Z3 Stalker Posted January 22, 2014 Share Posted January 22, 2014 JohnK your up with the hardware info. Link to comment Share on other sites More sharing options...
coffee break Posted January 22, 2014 Share Posted January 22, 2014 I was digging thur a box of books and found my copy of Racing and Sports Car Chassis Design by Costin & Phipps. Time for review. Link to comment Share on other sites More sharing options...
WestTexasS2K Posted January 23, 2014 Share Posted January 23, 2014 John k, I have been enjoying the thread my self. Johns car is not the typical S2k. The rear end looks like it was pulled from the XR7 model which is a completely different frame than the s2k. I m not sure when that car was built and why it was built the way it was. It looks like John is getting it sorted I am sure most owners would have thrown thier hands up long ago. Bravo for John sticking with it and doing the work to get it sorted. The S2k suspension isnt perfect, I'll be the first to admit it. It works pretty well for the most of us and can be adjusted to be a good performer. I have owned several S2ks and they all have been very capable cars. I have run with many Caterhams and passed many on the track. I have been passed by a few as well and a few Stalkers and a few Birkins and Locost models too. I have never driven a Caterham I assume they are jewel like precision driving machine. Since they are about 30k out of my price range I'll have to pass for a poor boy model. Keep up the work John its been educational for me. I have read most of those books you have mentioned. I havent attempted the software. I'm a little intimidated by it to be honest. Link to comment Share on other sites More sharing options...
JohnK Posted January 23, 2014 Share Posted January 23, 2014 Really not worth more than 2 cents here, --- but Most of us humans have some bit of a sense of "pride in ownership" - not because this or that thing that we own is particularly wonderful, but its OURS!, and us being human, that gives whatever it is some sort of value. And I'm sure that everyone out there has read some criticism and felt like the person just kicked their dog. I mean, its human nature. So is it really worth is to describe a situation that's only gonna send shrapnel out in to the List? Link to comment Share on other sites More sharing options...
AndyB Posted January 23, 2014 Share Posted January 23, 2014 "I have never driven a Caterham I assume they are jewel like precision driving machine." You must be talking new Caterham, My 76 Caterham is fun but "jewel like" it is not, more like a beach pebble Link to comment Share on other sites More sharing options...
speedwagon Posted January 23, 2014 Share Posted January 23, 2014 Really not worth more than 2 cents here, --- but Most of us humans have some bit of a sense of "pride in ownership" - not because this or that thing that we own is particularly wonderful, but its OURS!, and us being human, that gives whatever it is some sort of value. And I'm sure that everyone out there has read some criticism and felt like the person just kicked their dog. I mean, its human nature. So is it really worth is to describe a situation that's only gonna send shrapnel out in to the List? Taught my kids to be especially careful of the old junker next to us in the parking lot as it may be all the owner can afford or perhaps belonged to their grand parent who just died, and more valuable to them than our brand new rig. Same goes for wives or girl friends. I too have junk that is my pride and joy. Link to comment Share on other sites More sharing options...
JohnK Posted January 24, 2014 Share Posted January 24, 2014 (edited) - I made mention in the last post that I tried a bunch of different dimensions, going back and forth between reading and editing and plotting graphs and thinking about what the plots were telling me and ... before I got to SOMETHING. And this is to stress that the thing you have to face here is that there's no correct answer – you just get to the point where you've explored the consequences of many different arrangements, and recorded the results of each, and actually built stuff to see what is and is not physically possible, and you get to where you have so many results that you can lay them all out on a table, find that you can arrange them according to some logical scheme, and then think about it all. And after a while it becomes perhaps even obvious what seems to be a good direction and what's more likely to work, and what you can and can't have. And you think to yourself, “If I had access to O'Connell's facilities, https://www.dropbox.com/s/edccxybb5nq2pgr/oconnell.pdf?dl=0 I could actually test and measure how ...” But you don't, and you see what seems, given what you've learned and think you understand, to make sense and go ahead with it hoping that it just might turn out like you hope. Math and Physics and the other Sciences don't exist to give you what you want, they are just tools you can use to understand what's real and what's pretend. Here's an overview diagram of what I started with and what I came up with in the program, the top panel being the result, the bottom what I started with. https://www.dropbox.com/s/ovztammlmfr6p3i/Before-After.JPG?dl=0 (it's really more accurate to speak of “the MODEL” I constructed using the program and my data, because the technology allows you to create a virtual MODEL of reality. And if you've done it right, the two are damn near identical, which is wonderful because the MODEL is enormously easier to work with. - and it being computer technology, the only thing you get dirty is the air. . . “^&*#W@% keyboard can't spell!” ) In this diagram, most obviously the upper a-arms have had their outboard ends shortened and their attachments to the uprights raised, both quite a bit (5 1/2” and 2 15/16”, former and latter). You can also see that the roll center has moved higher which means there will be more lateral weight transfer (Tune... pg 36) and more jacking force (Tune... pg 38,39). This is isn't desirable because it decreases traction by loading the outside wheel at the expense of the inside, and pivots the chassis upwards on the outside wheel lifting the chassis with the greater jacking force which brings the outside wheel into droop. I'll guess that this could be improved my moving the inside suspension pickup points but on my car, there's either there's just no space to move into in that area, https://www.dropbox.com/s/b7ph8puk31rwied/HBrake_suspClear.JPG?dl=0 and https://www.dropbox.com/s/5em3bmzkt6g7qqf/Links-lower-clearance-inboard.JPG?dl=0 or there's not structure available in that area that you would want to place a clevis, into which you'd feel comfortable feeding loads. https://www.dropbox.com/s/05cq2ssgwwbxmzt/Links-Fwd-inbd-Pickups-space.JPG?dl=0 One thing that's interesting to look at is https://www.dropbox.com/s/5tsk9yc0zs9wt9u/capture_5-5_2-973_15el_0rot.JPG?dl=0 where the program's view is elevated 15 degrees and reveals the geometry of the inboard suspension pickup points. On the right you can see that the links are all just a bit shorter and the right upper rear link is noticeably shorter. While my main concern is whether this is going to result in any weirdness in how the right rear corner of the car behaves, I can't help but appreciate that things like drivetrain asymmetry can really bedevil anyone who's attempting to design a nice clean chassis, assuming that's where these differences came from. - The dimension changes I came up with were driven by two things. The first is what Smith had to tell me, and you can find drawings that look just like these in Tune... and his explanation of why this is what people run. The second was the car's space constraints. Smith's explanations and illustrations and results made it clear what behavior the various geometrical arrangements produced, the nature of the goal and the tradeoffs of the different choices. So he provided the framework for staying oriented, but without giving any dimensions. Potential dimensions that could be tried were determined by the car's layout. The program again proved its usefulness by allowing me to test the effects of changing a length or height without having to go to the car and change a part and measure the effect of the change. But recall, that I'd gone to no small amount of effort measuring the car with a high degree of accuracy (for a hobbyist working in his garage), so I was working with a model that represented reality fairly closely. And, of course once I found a path that looked promising, I had to go out to the car and measure to see what was living there already, if anything. One other thing that I used to help me understand things so I might be able to avoid shooting myself in the foot was to go out to a Subaru dealership and find an Impreza WRX up on the rack that I could take some pictures of for thinking about – the WRX being the source of the rear suspension parts. https://www.dropbox.com/s/okddp9wlvngbi5v/Subaru_Hub_InSitu-Best.JPG?dl=0 - Expectations ruined again. One of the reasons I found this particular car attractive was that it had an IRS instead of a live axle – advantages in lightness, suspension tuning capability, LSD, .... Well although the differential, axles and uprights are from the Subaru, and very stout members all, they were designed as a STRUT geometry, not an IRS and, as you read others say in this area, STRUTS are for cost-savings and not handling excellence (just ask Porsche). More importantly to me the pieces were DESIGNED to operate as a strut. Without getting too far into it, the strut that's connected rigidly to the top of the upright (that big lug that sticks straight up from the top of the upright that my car attatches its upper a-arm to) keeps the upright traveling vertically and the lower supporting assembly provides a longitudinally vertical triangular plane to form a support that aids the strut in keeping the wheel well controlled in its movement. Particularly the radius rod, going to the left in the picture, is in this plane with the lower a-arm above it since it attatches via a clevis to the lug on the bottom of the upright directly below the lower a-arm, and the radius arm is long, so it has a shallow arc. On my car the radius arm is short and way inside the hub which causes it to twist the hub as the hub moves in Ride, which causes rear Ride steer – which is bad, if you consider your rear end is steering your car as it chooses to when it goes over bumps as bad. With a lot of work you can fiddle with the alignment to keep this problem somewhat on the small side but it is designed in by the geometry and there's no fix I've found that's possible. Compromises! - After obsessing about the the correctness of the MODEL, I got to the point of facing how I could move the outboard upper upright link to its new position. Most obviously, this involves making uprights with different dimensions at the top, just as indicated by the diagrams in the models. - Now the straightforward way of doing this is to carve a model out of wood, attach fittings to it, drill in some holes to seat the bearings for the outboard CV joints and test it in place of the existing upright with the new links. Wood is nice to work with, it's easy to cut and drill and can be built of glued-together pieces and is strong enough to stand in for real uprights when moving the suspension around during testing and of course you can verify that you have clearance, and if not easily modify it to fit. After you get your wooden models in the right dimensions and shapes, you have someone do a pair of castings from them (I actually have a shop that will do this right up the street!), preferably in magnesium, and then find a machine shop with a milling machine to put in the bearing seats and mounting holes and all and you got yourself a new pair of Uprights – and a rear suspension that just might work a lot better – but certainly will look VERY cool – hip, even. Now since I would either have to win the Lottery or rob a large bank in order to pay for doing this (and since winning the Lottery is likely to take an awful long time and I have never recognized any skills in myself that one would associate with making a good bank-robber) I inventoried my stash of 4130 steel and got a full tank of Argon for my TIG machine, and started finding wood and metal bits around the garage that I could tack on to the existing uprights to prototype a wood-metal model for testing and then to have these act as the dimensional references so that I could fabricate a pair of uprights instead of trying to create ones I can't possibly afford to do the right way. Reading Smith isn't the only thing I've found that can make my hair hurt. Looking at where this is going is enough to conjure up thoughts of the Dispair Squid (Red Dwarf, anyone?) https://www.dropbox.com/s/4e3r6fww1l5mufd/Links-Lateral-view-from-left.JPG?dl=0 Next: Facing reality and building prototypes. Edited December 28, 2016 by JohnK Changes mandated by DropBox Link to comment Share on other sites More sharing options...
MeteorMotorsport Posted January 24, 2014 Share Posted January 24, 2014 Hi All Hello from Wales. A true coincidence that I have come across your forum this afternoon and that one of the busiest topics is the Handling thread. I hope one or 2 of you have heard of my business and that I can be of some help and information. I wont try to sell you anything (I will have to bite my tounge on occasions I am sure when an opportunity stairs me in the face):chillpill: Please slap me down if I over step the mark. Me I have owned a 7 since 93. I have been Sprinting (Autocross to you guys) and hill climbing since 2002. I was the L7C Competition Sec for 6 years (Stepped down this year) and have a few FTD and competition wins to my name:hurray: Meteor Motorsport grew from my interest in the 7 and more particularly its handling. I raced MotoX as a kid and understood bump and rebound. I think this helps a lot. So as I seemed to have a well sorted car people asked advice - I would guide them toward a suspension supplier and so on - then I started to sell the dampers on set ups I specified. Now Meteor sells most of the aftermarket suspension to the 7 community in the UK. I found your site as I have been gaining more and more customers for your part of the world and thought I would introduce myself here.:seeya: Back to the discussion - Terry's very first post said under damped and over sprung - says it all about many many 7's - you wont find that with our dampers be they Penske, Ohlins, Quantum or Nitron. In fact our Nitron Spec is over 4 times softer in rebound than the regular Nitron Setup in Rebound. So if you have any questions I will try and answer. Here is my Car https://www.youtube.com/watch?v=L-nRbWoYUGA&list=UU7RH1ud1FpNj4DJ7DBWZggQ&feature=c4-overview :auto: Link to comment Share on other sites More sharing options...
jlumba81 Posted January 24, 2014 Share Posted January 24, 2014 (edited) So a question to the suspension gurus. What damper adjustment will help with bottoming out when hitting frost heaves at 70-80 mph range? I had issues with the front bottoming out going up the bumps and the rear bottoming going down them. It made for and interesting game of throttle control whenever I saw the ripples in the road. PS forgot to add that its a Caterham SV with the stock suspension. I do have some AVO adjustable shocks that I bought off another member. Still haven't gotten around to getting them rebuilt tho. Edited January 24, 2014 by jlumba81 Link to comment Share on other sites More sharing options...
JohnK Posted January 25, 2014 Share Posted January 25, 2014 Part 7a1, 1 of 3. This is the really creative part of all of this because there's such a huge gulf between what you are trying to accomplish and the end point, plus the fact that there just aren't any guidelines on how to proceed in these circumstances. Much of it isn't explainable in terms of any theory or practice or by following certain rules of thumb – you pretty much write the script as you go because, in this instance particularly, you're building stuff in mid-air. I expect the things that I experienced when I was being a scientist doing basic research on the nervous system have been of the greatest help since science is all about starting with a blank sheet of paper too. None of the stuff that's below is from a text I've ever seen. All of it proceeds from sitting down, looking at what I needed to find out and then figuring out how to cobble something together that might tell me what I needed to know, if I was careful and paid attention. What follows is probably like what people did 30 or 40 years ago, and it's really slow work and very error prone – and then there's always the thought that it might not work, but that happens to the big guys too. I hope that some of the approaches and pointers I provide make sense and are of interest. I know from my experiences that such things as follow are generally useful when doing other kinds of work on a sports car. A bit of current perspective: Today, a person doing this would likely be starting work with a 3-D model of a chassis created from a file of data that described the chassis to the particular program, and the person would probably participate in the design of the chassis and places would be identified where pickups could be attached and the whole thing would be done virtually. The work would go to another computer that ran the equipment that built the suspension pieces. The chassis would be a tub made out of composites and might provide suspension links either built-in as stock, or as per buyer specs – can you say 'expensive'? Also, some of this kind of work can be done with WinGeo3. In such circumstances, you can start with the behavior that you're after (camber curves, weight transfer values, …all the stuff that Milliken & Milliken teach and Mitchell shows you how to do with his program, and Smith teaches you what they mean to a team manager making his cars more competitive) and the program will allow you to define the dimensions of the physical pieces that will deliver those handling specifications. - My experience with this kind of environment (outside of WinGeo3's scope) as it's done today had to do with the brake system I developed for my car. Starting with a blank sheet of paper, a few physical measurement, a CAD package and a text book on brake systems by Fred Puhn. I drew (drafted, actually) the system fitting all the parts together as I went and ordered the parts using the specs from the file from THREE different vendors one of which was a machine shop to whom I provided a CAD file that his NC Mill could read – all to fit an existing upright and an existing wheel from which I took the basic measurements. When all the parts showed up and I sat down and assembled everything, and everything fit together perfectly – including the 0.020” clearance between the wheel and the caliper, just as I designed. 20 years ago this could only be done by GM or Boeing. Now you or I can afford to do it and it keeps getting cheaper and cheaper. WinGeo3 is a start in this direction, because its a lot cheaper than your average CAD package, but someone has to provide you with the data that describes the chassis or you have to get the measurements yourself like I did, and WinGeo3 doesn't tell you you've run into anything or that the bits of the mechanism collide in the way that a CAD package does. Next: Part 7a2 Where to start. Link to comment Share on other sites More sharing options...
JohnK Posted January 25, 2014 Share Posted January 25, 2014 (edited) Part 7a2, 2 of 3. So where to start... Looking at https://www.dropbox.com/s/4e3r6fww1l5mufd/Links-Lateral-view-from-left.JPG?dl=0 we've got two rod ends staring at us at the top of the upright and those rod ends have to go up nearly three inches and in five and a half – (but when I began this, at this stage, I didn't know this yet and had to find a way to find out that/if I could actually get them to live there.) Clearly the only available structure to start building on is that lug where the links currently insert, but what the dickens to put there to hold them in a new and relatively distant position? I already found that the purpose of this lug (I. e., what the engineers designed it to be strong enough to do) is to be bolted to the bottom of a strut which meant that it had to be able to deal with some lateral, some longitudinal, and a large vertical forces. This is worth a back and forth comparison as I'm doing right now as I'm writing. https://www.dropbox.com/s/okddp9wlvngbi5v/Subaru_Hub_InSitu-Best.JPG?dl=0 That lug is clearly a hefty structure (I know from welding it that it's cast steel), - - - and besides that, what else have I got since the lottery and bank-robbery solutions seem to be out of the picture. I also reassure myself that no car like mine has broken a lug off an upright used in the manner shown in this picture. - Gathering stuff to experiment with. Speedway sells pretty convincing shock clevises that I've used and I'll put two of these into the mix and figure out how to sit them on something that'll point them toward the the links' origins, and search around in the spare parts for this something that will to sit between them and the upright, and whatever might connect to the upright. I also located some links I replaced earlier that are shorter and just about the right length and some cheap original rod ends of the right size – and anyway the links are pretty cheap if I need different sizes (unless you buy good/light/strong/beautiful ones from Woodward). (Here's the first of perhaps several places where you have to worry being overcome by hysterical laughter.) I happened to have some very hi-tech 1” diameter curtain rod (Lowe's finest) about that I drilled long-ways and fed 1/4-20 threaded rod through to serve as an arm off the lug (replacing the existing bolt+clevis assembly) and a piece of 5/8” plank cut to size I can glue to the wooden rod if my clamped together arrangement shows promise – ta-DAH - a platform for the clevises to sit on. ~/Desktop/WORKING/MockUp00.JPG https://www.dropbox.com/s/h5didx6d96duzbh/MockUp00.JPG?dl=0 What you're looking at here is the right side of the car, looking down the axle, head inside the fender well. The lower a-arm and radius rod links are in place (as they were, adjusted following this suspension being correctly aligned) so only the top of the upright is free to move about. Here I'm just beginning to explore where the rod ends are going to be now that they're at about the length I calculated with the program and how I'm going to be able to raise their position so that outboard end of this a-arm is 3” higher than the existing one attached to the lug on the upright – and how to measure, that what I'm about to build, is actually delivering that. Digression: a few paragraphs that are important. Background/Supporting stuff: Reference approaches. The Red diagonal on the right is a dummy shock that I built a set of and that are just plain very useful for holding things in place while you're working on the suspension, and they help to keep you from damaging anything by accidentally dropping assemblies you're working on. Holes are drilled for locating pins so you can hold the suspension at full Bump, full Droop and Normal Ride Height positions, and the ends have cheap rod ends and jamb nuts so you can fine tune length. This is my second set and such things are good to build when you've just bought your first TIG welder and need little projects that don't have to look pretty that you can use for practice and will probably do a second or third versions of as your work gets more involved and you learn more and grow your skill set. Building such things also serves an important function because thinking through what you need such a thing for and what it should do as you use it helps you form a better idea of the work you're attempting, and to be able to see further down the road which is the sort of seeing that allows you to avoid disasters or a damaged car. - While we're talking about positioning the suspension it's a good time to consider other references. All the stuff done with the program references the ground when positioning the parts not to mention reference locations that are on the car itself (like its centerline based on the one the collection of inboard suspension pickups allow you to define accurately), so it's necessary to develop a system of some sort to insure that you can accurately determine where you are when you have to adjust anything. I have this setup procedure that I wrote up along with a little diagram that I keep handy for reference whenever I do anything with the suspension, which means the car will be on jack stands and the wheels in droop, and I have to take all of that into account if I want to pull the shocks and change, say, camber. It serves as a guide to take into account things like where the bottom of the chassis is with respect to ground when you've got the car on jack stands and identifies the different bits on the car/suspension to measure from to see where things are... things like being able to position the wheel at Normal Ride Height is important whenever your doing anything with the suspension, and if you're inaccurate, the car doesn't deliver what you are after or may confuse efforts to track down another problem you're trying to solve. E. g., one bit that's useful on my car is a 5/8” bolt that runs fore-aft through the lower part of the upright, it's a good reference for the the ride height since, if you spend a moment looking at it you'll see that it doesn't change its Ride Height position with camber change. Things like that are useful and help you actually get what you do the work in order to get. (Doing this I think of a guy I used to spend an evening talking with every once in a while who does stuff like this, except on El-primo machinery for real money at Zakiras Garage - and I'm sure if I showed him what I was doing he'd walk away thinking to himself, “They really shouldn't let people buy tools so they can try to do a Mechanic's work.” I can't describe how accomplished he was/is – and the experience of talking with him has kept me permanently humble about my little achievements). Keeping the project from getting out of hand or failing altogether. You might go back to the first photo and appreciate that, while this is a really early picture, It shows pretty well where things go - and the key here is that that lug at the top of the upright and the two links that constitute the upper a-arm and insert on the lug, all wind up fitting within the notch in the chassis directly above it. More exactly, I've found that when the car is aligned (and aligned means, among other things, that all four wheels sit exactly at the corners of a rectangle 56”x 88”, and the centerline of the car as defined by plotting and resolving the locations of the inboard suspension pickups (some of which are not reliable indicators on my particular car) is identical to the centerline of the rectangle, and that the rectangle you build as a reference isn't in reality a rhombus, ) the rear wheels wind up directly under that notch in the chassis and the lug+links are centered in that notch at full Bump. Now, since only the top a-arms are targeted for change, the lower a-arms and the radius rods (those fore-aft links that keep the uprights rotated in position about the Y axis so that the top of the lug is in the position it is, (this position also minimizes the geometry's inherent Ride steer) ), all three of these lower links remain as they were when the car was correctly aligned. This is very fortunate because it means I can count on the fact that, whatever I fabricate, as long as I keep that lug oriented correctly within the notch, I will not have moved the suspension from its normal range of operation and nothing will come back to bite me by running into something I didn't want it to, since the only thing that will be altered is the camber curve generated when the suspension moves in Ride. All I have to do is ensure that what I fabricate to move the ends of the upper a-arms to their new location keeps the upright in the center of the notch This is also very important because the chassis tubes that form the notch limit the maximum Bump – if the lug, and more importantly the axle, is moved fore or aft, the upright will be limited in Bump movement – by running into the chassis! Whew! I intuitively got to this understanding when I did the work, but it sure wasn't something I was able to reason out beforehand and this is the first time I sat down and articulated it. Next: Part 7a3 Back to the prototypes Edited December 28, 2016 by JohnK Changes mandated by DropBox Link to comment Share on other sites More sharing options...
JohnK Posted January 25, 2014 Share Posted January 25, 2014 (edited) Part 7a3, 3 of 3 Back to the prototypes: Here is another shot of the same from a different angle so you may have a betters sense of things' orientations: https://www.dropbox.com/s/az4gmvz1hko1p4w/MockUp01.JPG?dl=0 The following shows the same setup except from within the chassis. https://www.dropbox.com/s/xrmj5sjfa***t7r/MockUp00-from-inside.JPG?dl=0 Links are attached to their chassis pickups and their lengths are about right, so this is somewhere in the ballpark, but I have no idea about height here. Second iteration of the prototype, and a new set of issues: prototype is glued together and the clevises are mounted on vertical supports that hold the clevises upright, and are in-line with the links and spaced so that they can be assembled as-is on the platform. https://www.dropbox.com/s/vnn2m2cr7ijlpa0/MockUp13.JPG?dl=0 My efforts are finding that, in order to get the height that is specified by the model, the clevises need to be mounted both on the top and stood vertically on the platform that's attached to the upright lug. Also these efforts have found that angling the platform that the clevises are mounted on upwards provides a means of adding more height to the clevises while still managing to clear the chassis tubes in the notch. https://www.dropbox.com/s/ug72mas8vtnfos7/MockUp16-from-outside.JPG?dl=0 Shows the 2nd iteration of the prototype from the outside and https://www.dropbox.com/s/f36347sqs70e0b5/MockUp118-positioning.JPG?dl=0 shows what I did when I got to the point of closing in on the target dimensions. Not shown due to the glare are that the block has a value on it*. I made a number of them each of different heights: idealy one is 1-1/2” tall, and the other is 2-1/2” tall. I'd set the upright lug on the scissors jack with the 1-1/2” block on it and then wind the jack to set the reference point to the height from the floor that, translated by the arithmetic in my notes, would move the right rear wheel to Normal Ride Height, then if I removed the block without changing the jack position, the wheel's position would be at full Droop and if I put the 1-1/2” block back under the upright and the 2-1/2” blocks on top of the 1-1/2” block, the suspension would be at where the right rear wheel was at full Bump. Net, it's worth cutting and labeling the blocks and swapping them out instead of measuring and adjusting each time you do something different with the related potential of making mistakes along the way. *You can see this better on MockUp01.JPG above. - There's another important reason for working with these dimension closely – speaking of things helping you see further down the road. In my initial build of my 'kit'. when I put the rear fenders on the car I found that the left one was quite a bit lower than the right due to the chassis being more than a little lower on the left side (check my rear fender positions in my Site photos- I had to mount the left one higher making it proud of the upper chassis tube). Also related to this, when I specified the dimensions that Koni wanted in order to build my shocks, I did so without the fenders on and found that on BOTH sides the of the car the fenders limited the 17” diameter wheels to way less than what I thought was available – What this means is that hitting a bump which takes either shock to the bottom of its stroke would have caused either fender to be pushed off the car by a wheel or perhaps also lock up the/a rear wheel(s), and that this is more of a problem on the left side than the right. Now the shocks I have have spec'd Silasto bump rubbers that allowed me to design an extra spring into the shock. These bump rubbers allow a progressive spring rate for, on my setup, the last 1/2” or so of travel before the end of the stroke of the shock (going solid) is encountered at full bump – very handy if you think it through – you can run a real low/soft spring rate for excellent following of the road by the wheel (not to mention getting a really comfortable ride to boot) without the cost of a hard landing if you run into a situation where you use up all the shock travel, and especially, no instant loss of traction at that wheel like you'd experience if the shock just bottomed solidly and all of a sudden. Finding out about these new dimensional constraints was a result of paying close attention to where all the parts are able to move to within their ranges, and the extent of the ranges involved. The shock-fender fix was done by redetermining the allowable wheel movement and then reducing the bump stroke so that it would be full on the Silasto limit before a wheel hit a fender by using “packers” which are built-for-this-purpose washers that you put on the shock's piston rod between the body and the top eye. . Also, with regard to getting accurate measurements, a 1” steel plate (cast iron would be lots better but you can't weld to it) large enough to put the car on with maybe a foot of overhang all the way around to do this kind of work on solves a lot of accuracy issues, but if that is a bit much for your budget you can still do this. but more inexpensively. Buy some 1/8” wall, 2”x2” square tube and lay it under what you're measuring and it will get rid of what can be significant local/area variations in concrete floors. You should verify that your floor is indeed level, and you can figure out how to arrange the 2x2s – like maybe buy two that are 10' long and run them long-ways beneath the car and shim them level if you have to, and then put shorter 2x2s cross ways on top of them as needed. The more accurately you can measure, the better your car will work in the end. Next: Part 8 I finally get to do some welding. Edited December 28, 2016 by JohnK Changes mandated by DropBox Link to comment Share on other sites More sharing options...
JohnK Posted January 25, 2014 Share Posted January 25, 2014 So a question to the suspension gurus. What damper adjustment will help with bottoming out when hitting frost heaves at 70-80 mph range? I had issues with the front bottoming out going up the bumps and the rear bottoming going down them. It made for and interesting game of throttle control whenever I saw the ripples in the road. PS forgot to add that its a Caterham SV with the stock suspension. I do have some AVO adjustable shocks that I bought off another member. Still haven't gotten around to getting them rebuilt tho. All of the stuff I have been posting says I've learned that a Caterham is so highly developed it's out of my ken.... Perhaps the person in the post just prior to yours has some guidence that he can offer based on actual practice, rather than just theory, like me. The only guess that comes to mind is something called "jacking down" and if I remember correctly has to do with too much rebound damping keeping the shock from returning to full stroke - but it's just a notion. Link to comment Share on other sites More sharing options...
bigdog Posted January 25, 2014 Share Posted January 25, 2014 Hitting frost heaves at 70-80? Holy crap. There just isn't enough suspension travel in a seven to absorb that. What you need is a Baja race buggy. When I was riding dirt bikes we called what JohnK talked of "suspension packing" If one puts a too stiffly rated spring on then they will try to add more rebound damping to counteract the pogoing effect an overly stiff spring requires. In the street scene we (most folks anyway) have been brainwashed by the lowrider look. The super low F1 look works on a smooth track but not the street. So we have learned to prevent bottoming out on a suspension that has little travel by throwing on stiff springs and damping. It was an ingrained attitude that we fought hard to loose in dirt biking, where bikes had 13" of travel and guys were still throwing on too stiff a spring. Link to comment Share on other sites More sharing options...
JohnK Posted January 26, 2014 Share Posted January 26, 2014 (edited) A general technique suggestion: After I got the prototype 'done' and was able to use it to guide my building of the working piece, copying the dimensions, I realized I still had to make its mate, and since the left side of the chassis was off true it wouldn't be identical – and besides, left and right hand parts aren't swappable. I turned out (I was lucky) that the basics that I had assembled could be taken apart (screws are better than glue here because screws allow you to disassemble) and I was able to flip things over and re-mount the components into new orientatins. And I found I could re-apply several aspects of the development sequence. Nett: even when you're making progress/having fun, it helps to step back and think a moment or two about next steps , as well as build prototypes in as modular a way as possible. I don't feel that there's benefit to getting into any more detail about the prototyping although many details were in fact critical to ensuring that the result was correct. It seems that going on any more would just prove too tedious. If anyone's got any questions, please feel free to ask. Recall what I said about readers who predict an end to my little project in terms of smoking remains? Well, here 'ya go – a great opportunity! While the prototype was fine for testing the behavior of the setup, the final piece had to survive real-life stresses, and if it didn't, I'd find myself going down the road with a rear wheel hanging loose on one side of the car, the wheel, most likely, just before having been supporting the rear of the car on the outside while in a fast turn. So, “overkill” is the goal here. Speaking of overkill and in case anyone out there is interested, I captured a series of shots of the final assembly, the left one, hopefully enough so that one can resolve all the relationships satisfactorily. https://www.dropbox.com/s/9ee2407kzpy1f0h/01010021.JPG?dl=0 -#21 https://www.dropbox.com/s/6c0xstjfq8pvxsm/01010022.JPG?dl=0 -#22 https://www.dropbox.com/s/ue72hhpa6dvi9qq/01010023.JPG?dl=0] - #23 https://www.dropbox.com/s/00zmah1kluotx1f/01010024.JPG?dl=0 -#24 https://www.dropbox.com/s/hl8k4v9ud1zh6nb/01010025.JPG?dl=0 -#25 https://www.dropbox.com/s/kkr84c86pkttayd/01010026.JPG?dl=0 -#26 https://www.dropbox.com/s/rly4bgdtbr4ph53/01010027.JPG?dl=0 -#27 https://www.dropbox.com/s/1dfuc7gzvw0mfic/01010028.JPG?dl=0 -#28 https://www.dropbox.com/s/dlddhzbz8akzsn9/01010029.JPG?dl=0 -#29 https://www.dropbox.com/s/o0vjuwfxyyti71u/01010030.JPG?dl=0 -#30 https://www.dropbox.com/s/gw1absixckjymy6/01010031.JPG?dl=0 -#31 https://www.dropbox.com/s/i5ne9t4nb5wc4ph/01010032.JPG?dl=0 -#32 https://www.dropbox.com/s/n45kqvhaz799jmg/01010033.JPG?dl=0 -#33 https://www.dropbox.com/s/lfs192sv81mvt35/01010034.JPG?dl=0 -#34 https://www.dropbox.com/s/hkzxjfsrwpf2w6g/01010035.JPG?dl=0 -#35 My reasonings about matters of stresses and how to handle them proceeded as follows. -The lug on the upright is clearly stout, but the prototype feeds all the load into one point, and that point is on the rear-facing side of the hub, so the force of the wheel in Ride, which will be roughly along the axle, will act to twist the lug. Therefore I should build a support on the opposite side of the lug as similar as I can to what's already there. As you can see on #25-#28, this took some doing, and the effort was prompted to do so by appreciating how hefty the lug is. -The most fundamental job of this extension to the upright is to present the outboard upper suspension pickups to the upper a-arm 3” higher and 5-1/2” further toward the center line of the car. To do this it has to poke through a space in the chassis without, over its entire range of movement, running into the chassis. It partly accomplishes this by putting the pickups (clevises) out on the end and on the top of a platform, and angling the platform upwards. The gussets that support the clevises were oriented to be directly in line with the links when the wheel was correctly aligned to assure that all of the stress that they bore came in line with their plane. It is a truism that all the forces in a suspension like this are in line with the axis of the each link, and therefore the clevises should not experience twisting forces. -The construction of the diagonals supporting the platform at the clevis end was prompted by thinking, “And where are the forces going to be fed into this structure when I hit the brakes or dump the clutch?” Although such forces will travel in line with the links, forces such as these will not necessarily be balanced on the pair of clevises and thus may act to push the platform fore-aft, and if unsupported could result in a twisting of the platform. Hence the supports. I made them adjustable taking into consideration the closeness of fit at full Bump with the chassis and the possibility that the platform may need to be lowered for clearance reasons. Also it is conceivable that lowering the outboard pickup point of the a-arm may turn out to change the handling favorably under yet-to-be-discovered circumstances. The red structure (#24) is an earlier construction and was built to support the end of a 1/2” bolt that accepts forces lateral to the bolt, from the radius rod, shock/spring, and ARB. This structure supports the very end of this bolt which, as delivered, had only single-shear support and the bolt was unsupported from the face of the lug that you can see at the bottom of the upright to its end. The red structure also supports the 5/8” bolt running longways near the bottom of the upright, and which bears the loads imposed by the lower front a-arm link, previously in single shear. (Think; “single shear” = “heavy person bouncing on the end of a diving board”.) The first issue is failure of the part due to fatigue, the second issue is creating poor control by, in effect, adding another spring into the mix that will cause your wheel to move around in unintended ways. Next: About the fabrication and wrap up. Edited December 28, 2016 by JohnK Link to comment Share on other sites More sharing options...
JohnK Posted January 26, 2014 Share Posted January 26, 2014 (edited) Comments on the fabrication. I can not stress enough how incredibly versatile and easy to use the Miller DX 200 welder I bought has been in building this and other things. It was not cheap, it did take time to understand the significance of even some of the benefits it offers, and welding in general is a skill and takes practice. But using my past experience in oxy-acetylene welding, I found I could do previously unimaginable things: from building an internal sump for my fuel tank out of 0.030 aluminum sheet to welding 3/16” and even something as light as 1/8”steel to a large steel casting, to fillet (T) welding 16 ga. sheet to 3/16” stock without even worrying about burning through the thin sheet. (examples shown in numerous places in the collection of pictures in this post). Now I've seen a few people do incredible things with a gas torch, but it took them years and years of practice and that was their job. I bought this thing and with a modest amount of practice, could fabricate things as if I were an experienced professional welder, of which I am neither. This part added 2-1/2 lbs. to each upright which weigh around 24 lbs each, and the brakes are inboard so I'm likely still coming out ahead here on unsprung weight. (values from memory – probably close but need to verify 1/25/2014) Lots of times you'll weld something and the back-side will get covered with what I've heard called “mill scale” which is caused by oxidation of that surface from the heat on the opposite side of the piece. It takes away some of the surface of the metal and can leave hard deposits (this is not burn through from too much heat). This can be a problem if you're welding something to a tube and the tube will have a close-fitting bolt run through it – and you wind up doing a lot of work to clean up the inside of the tube before you can get the bolt through. I've has some luck in such situations covering the surface with copper-based anti seize. Copper next to steel doesn't weld and the copper particles on the backside of the weld tends to reduce or eliminate the formation of the mill scale. Standard industry practice is to have a second supply of the inert gas you're using (Argon, Helium, …) piped into the area where the back of the weld will be. This is the best, but is a lot of work. The platform consists of a set of 16 ga 1” square mild steel tubing welded along all seams, capped on the inboard end and welded without any breaks to a 3/16”wall 1” diameter tube. Clevises are formed out of 1/8”(?, at least) stock and supported by 1/8” mild steel gussets. The gussets are the features that limit the height to which the a-arms can be moved to without hitting the chassis at maximum Bump. Diagonals supporting the ends of the platform that I fabricated used solid rod ends that I had to machine myself (Reid Supply) and 4130 tube with mild steel plugs welded in, drilled and tapped in a lathe to keep things straight (not as easy as I'd thought it would be.) Positioning these on the upright and in the available space was quite a challenge because everywhere I seemed to look, something was running into something else and, in general, the available space was limited. I made the right side first and along with the need to get everything very close to where it had to be, to not only fit but also deliver the behavior needed, I wound up having to tack things with each or several bits in place on the car. Difficult to do. You may notice that the upright itself is irregular in that the side face of the lugs makes the platform tilt downward toward the front of the car. This means that the diagonals' clevises need to be at an angle, both at the upright and at the platform otherwise there will be pretty significant binding when you try to assemble things. While I got this part of the structure to assemble without difficulty, there was a lot of variation in the individual parts. In self defense, I wound up engraving the position of every piece (each tube, each rod end) identifying where that piece went by side, f/r position and clevis and vertical orientation so that I could assemble it free of strain (which you get when you bolt stuff together that doesn't fit correctly – assembling parts under strain is an classic way to get an exhaust system to break apart. Along with all of this was ensuring that the fabrication had the clearances it needed everywhere to be able to pulled in and out of where it fit in the car and to be able to be assembled. (Ever put something together and then find out that you couldn't get a bolt in or out?) Installed, there are several places where this could happened, if allowed, re the axle and CV joint, other suspension parts, … Tight! (Of course, if you've seen pictures of the engine compartment in 7evens WCM with dry sump and supercharger and extra heat exchangers, and all you're probably thinking, “Hey, this guy could probably play handball in all the space he's got to work with!”) - “The other guy's job is always easier!” After the local Metal Supermarket got to be just too much of a hassle to deal with (it's not really what one would call a 'supermarket', at least this one.) I wound up buying all my steel and aluminum from http://www.airpartsinc.com. They've got a wide range of stuff in wide range of dimensions, you only have to buy what you need, and they're very pleasant and friendly, and give great service. They stock a really wide range of tubing, and in steel it's all 4130/chrome molly and 'normalized' to aircraft spec, which means is what most folk call 'heat treated'. They made my work easier. At this point (late January 2014)I'm hopefully not too many months away from being able clean, prime and paint all the bits and install them. I have in progress a support I'm fabricating for the differential. And I'm desperately searching for a differential I can buy that has an LSD and 4.111 ratio - which the car really deserves. And, of course, am looking fwd to installing and testing out my little project. Should I make the headlines due to me and my car's new suspension's involvement in a spectacular crash sometime this coming summer, I hope you're listening to the news so you can say, “Hey, I knew that guy!” Edited March 8, 2015 by JohnK Link to comment Share on other sites More sharing options...
JohnK Posted January 26, 2014 Share Posted January 26, 2014 Hitting frost heaves at 70-80? Holy crap. There just isn't enough suspension travel in a seven to absorb that. What you need is a Baja race buggy. When I was riding dirt bikes we called what JohnK talked of "suspension packing" If one puts a too stiffly rated spring on then they will try to add more rebound damping to counteract the pogoing effect an overly stiff spring requires. In the street scene we (most folks anyway) have been brainwashed by the lowrider look. The super low F1 look works on a smooth track but not the street. So we have learned to prevent bottoming out on a suspension that has little travel by throwing on stiff springs and damping. It was an ingrained attitude that we fought hard to loose in dirt biking, where bikes had 13" of travel and guys were still throwing on too stiff a spring. My involvement with off-road and street bikes was so long ago it was mostly about just managing to get them started and keeping them running! I can understand balancing a stiffer spring with more rebound, but clearly you can only take that whole thing so far, but I'm thinking back that there was nothing that I remember that was like Silasto in my time - where you've got a selection of different bump rubbers so you can tailor what happens at the end of travel, and with the spring rate have kinda two different rates. People talked about progressive rate springs, but nothing I ran into would give both good following of the dirt for small bumps yet still keep a big bump from upsetting things other than really long shock travel. 'Course on a car, there's just not room for that. Interesting to think about it cause it's been a while, but I learned an awful lot about what it's like to go around corners on Bikes, maybe even more that on 4 wheels. Link to comment Share on other sites More sharing options...
bigdog Posted January 26, 2014 Share Posted January 26, 2014 I know that while the physics are a bit different between a bikes and a cars shocks. The theory is the same. But a bike gets so much more suspension loading in a corner. With dirt bikes having so much more travel, one can adjust to have initial softness to follow the small bumps. My Yamaha WR450 used a straight rate spring, but also used air volume (not air pressure) via oil level changes to create progressiveness in the last bit of travel. Riding a fast sport bike will certainly teach a person about the proper approach to corners. With smoothness being a key factor, trail braking technics, and learning that if your front washes out getting on the gas will help you regain front wheel traction. Which seems counter intuitive. Link to comment Share on other sites More sharing options...
JohnK Posted January 27, 2014 Share Posted January 27, 2014 I know that while the physics are a bit different ... - You're way beyond me. When I was enjoying bikes I'd never heard of that kind of suspension, let alone anybody having a formal approach to tuning that was available to mere mortals. The last new thing that I had any close contact with was the Yamaha DT-1 - a Bultaco Matador wannabe and the OW31 was the last road racer I knew about from close-hand contact. The other thing is that I haven't had anywhere near enough actual practice time, and none of it on a track - When riding a sport bike on the street you just can't commit yourself to a line without getting pretty suicidal - at least from what I've seen and where I've riden. So your having experience working with these pieces puts your knowledge way beyond what I can bring to the table in terms of the actual nuts and bolts practice - Another point, while I've enjoyed being able to leverage math and physics to get me in the ballpark on some issues - and it is very powerful -, but as I found out there is a world of stuff that just can't be done mathematically. An excelent example is the trucking company Diamond Heavy Haul. Take a look at their web site. The late Steve Engles (who I had the great good fortune to talk with several times) would build these collosal vehicles starting with drawings he made for his staff on the floor of his factory. Other companies would buy these "trucks" and try to copy them and their engineers couldn't make their maths work, not to mention the trucks they tried to build. Humans can solve, in their heads and based on experience and practice, the differential equations that define how our equipment works in the real world that the mathematicians haven't figured out yet - and may never. So while the stuff I learned from Carroll Smith and using the software is indeed pretty amazing, it only gets one in the front door. Smith talked in other circumstances about the importance to a team of having a really good test driver. My experience is that (some) engineers can get to act like religious wackos - if it's not in the textbooks it can't work or be true - which is simply idiotic. These people will be replaced by computer programs and people who know how to live in the real world. I envy that you have and have had the opportunity to work with the different pieces of hardware you talk about. Link to comment Share on other sites More sharing options...
bigdog Posted January 27, 2014 Share Posted January 27, 2014 I think you are selling your self short. But the bike scene is lightyears different than the car scene. Due to the huge power to weight ratio of a modern bike (dirt or street) Most bikers do not spend a lot of time messing with the engine. And most concentrate on handling. Which of course is (normally) quite the opposite to a car person. I would say that the vast majority of car people are only slightly aware that their car even has suspension. I've been fortunate that as a (now former) biker I spent a few years working at a bike shop. And since 1982 when I first started riding I've owned 38 bikes. I've had the racer bikes (Suzuki RG Gamma, Ducati 888 SPO LTD). Touring bikes (2 Goldwings, BMW K12LT) Dirt bikes (CR250R, KDX200, KTM 620 adventure, Yamaha WR450F) Even 2 supermoto bikes (KTM duke II, Husqvarna SM610) Link to comment Share on other sites More sharing options...
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