Lotus 7 Project Arrived

[MV8]

It would be based on the installed axle flange and wheels with the same tolerance as an alignment. Flange runout is typically less than .010". I forget the wheel run out. There is no need to fully weld a brace. 1/2 to one inch stitches every three inches is plenty for a brace. Long beads are more likely to warp. Weld a few, wait a few, wet towels to suck the heat out faster. Alternate between axle ends. Use enough heat for a fairly fast weld instead of a slow weld that has a greater heat affected area.

Edited January 19 by MV8

[ianashdown]

2 hours ago, anduril3019 said:

If the goal is zero toe and zero camber, what's a reasonable tolerance?

The Lotus S2 owners manual doesn’t quote any alignment figures for the rear suspension, probably because there is no adjustment.  It’ll be whatever the manufacturing tolerances of the Axle were.

 

I am certain that what the welding is likely to do, induce toe-out, is bad.  Some induced positive camber is not preferable, and I’ve heard of some deliberately inducing a small amount of negative camber.  Probably a trade of performance for potentially shorter life.

 

Ian

[ianashdown]

2 hours ago, MV8 said:

It would be based on the installed axle flange and wheels with the same tolerance as an alignment. Flange runout is typically less than .010". I forget the wheel run out. There is no need to fully weld a brace. 1/2 to one inch stitches every three inches is plenty for a brace. Long beads are more likely to warp. Weld a few, wait a few, wet towels to suck the heat out faster. Alternate between axle ends. Use enough heat for a fairly fast weld instead of a slow weld that has a greater heat affected area.

All good advice, thank you.

 

If I have to do this myself, which is looking increasingly likely, then I will build some kind of fixture.  I hoped to avoid this.

 

I’m going to follow the advice of Chris Beebe and use rectangular tubing rather than the 1/4”, or whatever, steel plate.  Too agricultural for my preference.  So there will be a minimum of welding and therefore less shrinkage.

 

All my fabrication experience has taught me that welds always have shrinkage and it’s better to build compensating for that rather than trying to correct afterwards.  Straightening is doable, stretching not so much!  Shrinkage in this case will induce toe-out what is never good in my experience.  I’ll have to think about how much toe-in to build in to the fixture unless anyone who has done this can relate past experience.

 

All part of the journey!

 

Ian

Edited January 19 by ianashdown

[IamScotticus]

I am getting closer to deciding to remove my brace plate.  Not for alignment reasons, and I don't plan on going over 150hp, but for safety. 

My brace plate is a big knife ready to slice into the gas tank if I get squished.

Edited January 19 by IamScotticus

[Christopher smith]

6 minutes ago, IamScotticus said:

I am getting closer to deciding to remove my brace plate.  Not for alignment reasons, and I don't plan on going over 150hp, but for safety. 

My brace plate is a big knife ready to slice into the gas tank if I get squished.

That is why I have an ATL fuel cell with internal bladder and foam.

[IamScotticus]

1 minute ago, Christopher smith said:

That is why I have an ATL fuel cell with internal bladder and foam.

That's a good idea.  Which model?

[Christopher smith]

4 minutes ago, IamScotticus said:

That's a good idea.  Which model?

 

4 minutes ago, IamScotticus said:

That's a good idea.  Which model?

 

4 minutes ago, IamScotticus said:

That's a good idea.  Which model?

It is the rectangular 8 gallon ATL sports cell like we always used for SCCA in other cars. But it is too big to fit in usual 7 place so we mounted it above the axle. Higher center of gravity of course. I think the custom ones can go behind axle but they are even more pricey. I was setting up to go D production racing but it took so long I felt too old for serious racing. Almost 80 now.

[ianashdown]

1 hour ago, IamScotticus said:

I am getting closer to deciding to remove my brace plate.  Not for alignment reasons, and I don't plan on going over 150hp, but for safety. 

My brace plate is a big knife ready to slice into the gas tank if I get squished.

You make a very good point on the safety of that style of reinforcement.  I like the tube much better, but then again, safety was never a 7 strong point!

 

I haven’t got to it yet, but I have some thoughts about cutting an access panel in the front of my original tank and fitting a custom made bladder, with foam.  I feel the sloshing of fuel can be felt in a car this light.

 

If there is any interest I’d be happy to see if a group buy could be arranged.  I have a long term contact in the fuel cell business and years of experience designing fuel cells, pickup systems etc.  We could also accommodate an internal collector tank with a high pressure pump for anyone running injection.

 

Ian

Edited January 20 by ianashdown

[IamScotticus]

@ianashdown

Sending PM

[SENC]

Here's how mine was done (likely when it lived in Australia), in the event it helps...

 

[ianashdown]

That’s an interesting approach.

 

Thank you,

 

Ian

[pethier]

16 hours ago, SENC said:

Here's how mine was done (likely when it lived in Australia), in the event it helps...

 

I don't think that would clear the fuel tank on my 1979 car.

 

All in all, I'm happy to have the deDion setup on my 1991.

[ianashdown]

My car seems to have had engine mounts made that move the engine back by maybe as much as maybe 6” (see attached).  
 

This car has a history of some form of competition, auto cross or similar, back in the mid to late ‘60’s so I wonder if shifting the engine was a thing back then.  I’ve heard, and it would seem logical, that it balances the F/R weight distribution to close to 50/50.

 

Is this a mod worth keeping, understanding that it is not original, but is an in-period modification?  I believe the original mounts are in the pile of part somewhere.

 

Ian

[pethier]

I believe this is just the sort of thing that would have been done.

 

I suggest you measure up to see which setup was used.  If everything fits with the engine in the rearward position, I see no reason to not do it.

 

That said, my 1991 car with the engine far-enough-forward to stick under the nose does have more than 50% of the weight on the rear wheels.  This is without driver and without the spare tire and bolt-on bracket.

Edited February 6 by pethier

[wdb]

Those mounts do look a bit longer than the ones in the picture below, which is from this thread: https://usa7s.net/ips/topic/15043-ford-kent-engine-dry-sump-mount-bracket/

 

 

However I wonder if that difference is due to block width. My understanding is that there are various widths in Kent blocks. Also I doubt it is a 6 inch move even if they are longer; to move the block that far back and still clear the oil pump, there would need to be a pretty big curve in the tubing.

 

[ianashdown]

It’s going to take some study for sure.  I’m surprised to hear that you’re at 50% with no drive or spare when the engine is well forward.

 

I think some the secondary difficulties may sway me against.  No available exhaust, gearbox mount to name just two.

 

Hmmmmm . . . 
 

Ian

[anduril3019]

15 minutes ago, wdb said:

However I wonder if that difference is due to block width. My understanding is that there are various widths in Kent blocks. Also I doubt it is a 6 inch move even if they are longer; to move the block that far back and still clear the oil pump, there would need to be a pretty big curve in the tubing.

The only width difference is on the 711M block which is the uprated crossflow block introduced in 1970. The left side motor mount bosses are taller, 1/4"-3/8" I think, but I'm not 100% sure on that. I'm not sure what Caterham did for new engines, but often when this block is used as a replacement or upgrade for an older engine, the bosses get milled down then drilled and tapped deeper if needed. Otherwise, a modified mount is needed.

[Joe Petty]

I just looked at my mounts and I think yours look like they are giving slight setback.

 

On the right side, my bolt pedestal is directly in line with the center of the oil pump plate.

On the left side, the pedestal is maybe 2" in front of the generator backplate.

Both mounts use straight bars.

 

I saw something onetime about moving the engine back a couple inches.  Don't remember if this was a racer mod or a factory thing.

Might be early, but when you get the engine in the front belt pulley only clears the frame crossbar by an inch or so.

There is not much clearance between the starter and the footbox on a RHD, so I don't see how the engine could move back.  Not so big a problem on LHD.

 

Always an adventure!

 

Good Luck, Joe

[ianashdown]

4 hours ago, Joe Petty said:

I just looked at my mounts and I think yours look like they are giving slight setback.

 

On the right side, my bolt pedestal is directly in line with the center of the oil pump plate.

On the left side, the pedestal is maybe 2" in front of the generator backplate.

Both mounts use straight bars.

 

I saw something onetime about moving the engine back a couple inches.  Don't remember if this was a racer mod or a factory thing.

Might be early, but when you get the engine in the front belt pulley only clears the frame crossbar by an inch or so.

There is not much clearance between the starter and the footbox on a RHD, so I don't see how the engine could move back.  Not so big a problem on LHD.

 

Always an adventure!

 

Good Luck, Joe

Hi Joe,

 

Thanks for the references.  I’ve never seen this car with the engine in so this was a big question.  I have the frame drawings and was looking for some reference to engine position, but there are none.  It’ll be while before this goes back together, but this info will be a good check.  I will try to find the other engine mounts, there’s also a fixture to make more, and see if there are differences.

 

My guess is this was an autocross car or similar, but some very low level as the standard of workmanship of the welded-in roll hoop was very, very poor.  It would not pass tech inspection, not even close, these days!  My thought is that moving the CG rearwards may have improved turn in response.

 

Ian

[SENC]

I'll be at my shop later this morning and will grab a couple pictures for you for comparison, but as others have suggested I think you'd have noticed other chassis or aluminum mods if they move things back 6".  The most visibly obvious would be gearshift location in the car, exhaust outlet hole in port-side aluminum, and chassis/firewall entry point for the gearbox (I don't recall exactly, but I'm certain my gearbox couldn't go backwards anywhere close to 6" before fouling on the chassis).