MightyMike Posted February 22, 2010 Share Posted February 22, 2010 I took off my center console to get it reupholstered and upon removal, discovered there are no driveshaft loops. Is this normal? http://i48.tinypic.com/2eg61vn.jpg Link to comment Share on other sites More sharing options...
11Budlite Posted February 22, 2010 Share Posted February 22, 2010 Mike, I'm not sure when Birkin started installing driveshaft hoops, but the only cars I've seen them on from the factory were the IRS chassis. Your car would not have had them from the factory. From memory, I ended up bending some 1.5" x 3/16" steel around an old Lucas generator to form a hoop, and had it welded to the frame. Sorry I don't have any photos at work. Check out Dick Brink's website for some detail photos from a later IRS chassis: http://www.texasmotorworks7.com/webtemplate.aspx?IID=575025 Link to comment Share on other sites More sharing options...
s2k7 Posted February 22, 2010 Share Posted February 22, 2010 (edited) xxx Edited January 24, 2014 by s2k7 Link to comment Share on other sites More sharing options...
MightyMike Posted February 22, 2010 Author Share Posted February 22, 2010 I'm definitely going to weld in a couple of loops. Seems rather dangerous not to. Link to comment Share on other sites More sharing options...
Ian7 Posted February 22, 2010 Share Posted February 22, 2010 Curious about the Birkin relative to my caterham. Where's the "backbone" vertical bending stiffness of the chassis since it has no structural tunnel down the centerline? I guess its just the elbow-level side frames? Why not put in a full tunnel while you're at it? Just a few extra tubes, and you're exposed already.... Link to comment Share on other sites More sharing options...
slngsht Posted February 22, 2010 Share Posted February 22, 2010 Curious about the Birkin relative to my caterham. Where's the "backbone" vertical bending stiffness of the chassis since it has no structural tunnel down the centerline? I guess its just the elbow-level side frames? Why not put in a full tunnel while you're at it? Just a few extra tubes, and you're exposed already.... i agree. every seven I had seen before (granted, not many), have a fully boxed center tunnel. Link to comment Share on other sites More sharing options...
paulmpetrun Posted February 22, 2010 Share Posted February 22, 2010 (edited) Mighty, I'd build two pronto! One for each u-joint. Your probably better off building something VERY strong rather than buying a universal one from summit or elsewhere! Mostly because if these fail on a regular car, theres still lots of hard bits between the driveshaft and your soft bits! Not so on a 7... Build them as close to the shaft as possible, that way if it fails they are contained and can only continue to spin, and not flail around. I had the front u-joint EXPLODE on my R1 powered seven at the redline in 6th on a track! Thankfully no passenger, as it ripped through the 3/4" square tubing cage that surrounded it like nothing was there. Then smashed my fire extinguisher, and mangled my passenger side(left side, car is RHD) kirkey seat. The only thing that saved me was the mounts for my driver seat. I made them out of 1" square tube with 1/8" wall. Its what I had laying around in the garage when building them, and wow was that lucky. The 1" tubing was shaped like a banana, where the shaft hit it, and was then deflected to the other side. On the new 7, the driveshaft loops are 1" round tube with 1/8" wall. Definately not something to take for granted in a 7. Good luck and enjoy! Paul Edited February 22, 2010 by paulmpetrun more info came to mind Link to comment Share on other sites More sharing options...
slngsht Posted February 22, 2010 Share Posted February 22, 2010 (edited) on mine, i have a 1" square tube .065 wall for the tunnel structure. there are two 3/8" plates with oblong holes near each end of the driveshaft. I'm pretty sure it won't tear through those. All my fuel, battery, brake lines are passed inside a steel channel along the length of the tunnel to protect them as well, and that steel channel sits on top left side of the tunnel, where it would stop any fragments flying up my way. yes, my car is heavy. Edited February 23, 2010 by slngsht Link to comment Share on other sites More sharing options...
DeanG Posted February 22, 2010 Share Posted February 22, 2010 On the positive side the hidden areas look clean. You have a very nice car. Link to comment Share on other sites More sharing options...
Boxologist Posted February 23, 2010 Share Posted February 23, 2010 i suspect most Caterhams and Birkins unless spec'd w/ a driveshaft hoop won't have them. Link to comment Share on other sites More sharing options...
Mike Rohaley Posted February 23, 2010 Share Posted February 23, 2010 Per my reference books, in 1985 Caterham made extensive modifications with braced longitudinal tubes to the transmission tunnel to increase torsional stiffness. It is a bit more complex than two hoops but essentially serves the same purpose should the drivshaft go flying. Link to comment Share on other sites More sharing options...
MightyMike Posted February 23, 2010 Author Share Posted February 23, 2010 Appreciate comments and suggestions - car is going in the shop by the end of the week. Besides the driveshaft loop, I will likely get a metal cover fabricated to replace the fiberglass cover. Link to comment Share on other sites More sharing options...
MightyMike Posted February 23, 2010 Author Share Posted February 23, 2010 On the positive side the hidden areas look clean. You have a very nice car. A little elbow grease goes a long way. Link to comment Share on other sites More sharing options...
slomove Posted February 23, 2010 Share Posted February 23, 2010 (edited) Per my reference books, in 1985 Caterham made extensive modifications with braced longitudinal tubes to the transmission tunnel to increase torsional stiffness. It is a bit more complex than two hoops but essentially serves the same purpose should the drivshaft go flying. Well, http://www.californiacaterhamclub.com/chat/attachment.php?attachmentid=434&d=1213062216 http://www.californiacaterhamclub.com/chat/attachment.php?attachmentid=436&d=1213062216 The Caterham version may help but is obviously not perfect. The driver was lucky that the shaft escaped on the passenger side. However, this is a 260 hp Cosworth engine with sequential transmission and very sticky tires, probably driven without clutch under race conditions. I ended up weding a more substantial cage to my Birkin: http://lh6.ggpht.com/_242PlvPtVpE/S4NHjiwciMI/AAAAAAAABWc/W93fs9idXFw/PropshaftPrison.jpg Gert Edited February 23, 2010 by slomove Link to comment Share on other sites More sharing options...
southwind25 Posted February 23, 2010 Share Posted February 23, 2010 Our Birkin did not have one, it does now! Link to comment Share on other sites More sharing options...
Mike Rohaley Posted February 23, 2010 Share Posted February 23, 2010 This photo is of the Caterham CSR chassis but the center tunnel is of the same design as the standard chassis. Triangulation is the important difference from a couple simple loops. Link to comment Share on other sites More sharing options...
scannon Posted February 23, 2010 Share Posted February 23, 2010 (edited) This photo is of the Caterham CSR chassis but the center tunnel is of the same design as the standard chassis. Triangulation is the important difference from a couple simple loops. Any opinions as to whether loops should be added to this frame or would the frame itself would contain a failed driveshaft? I'm wondering if I should loops them to my Caterham SV which is the same chassis except it has deDion rear suspension instead of the CSR's IRS. Edit: I talked to Ben at Caterham USA and asked if any Caterhams came with driveshaft loops. He said the only ones were R400s with sequential transmissions. Those aren't a loop like we have been talking about but rather a steel plate with a hole for the drive shaft which is riveted to the transmission tunnel. Ben said the only Caterham driveshaft failure he had heard of was a 300 hp Cosworth with a sequential transmission. It didn't have the plate or loops and the chassis tunnel contained the driveshaft. It is the shock of clutchless shifts on the sequential transmissions that cause the U-joint failures. I don't think I am too worried about a driveshaft failure on my car. Even with the quickest shifts I can manage, the sprung hub of the clutch disk will cushion the shock. I have an RX7 front U-joint and the stock Caterham rear U-joint connected by a high strength steel shaft. I mentioned MightyMike's Birkin with no chassis tubes around the transmission or driveshaft and Ben said that the Series 2 Lotus 7s were that way and in fact the live axle Birkins were direct copies of the live axle Lotus 7s. Edited February 23, 2010 by scannon Link to comment Share on other sites More sharing options...
MHKflyer52 Posted February 23, 2010 Share Posted February 23, 2010 Here is a drive shaft gard that you can have made up or you can make youself out of some scrap plate. If you need to change the dimensions to fit your trans tunnel it is easy to do. I would make two of them and place them so they are 2 inches aft and fwd of the universals containing the driveshaft. Just my thoughts and hope this helps. If you want a drawing for this to take to a shop and have made e-mail me and I will make one to your dimensions for you. Link to comment Share on other sites More sharing options...
MichaelD Posted February 24, 2010 Share Posted February 24, 2010 FWIW, Caterhams come with boxed in tunnels. That is one of the items that lead to a higher cost. Folis Jones did a really nice job boxing in the tunnel on his Birkin after seeing how well my Caterham is finished off. I would suggest you contact Folis n57fj@earthlink.net I am sure he can provide photos and is usually very willing to share information with another Sevener. I agree with DeanG as to how clean your car seems to be. It must have been cared for. Link to comment Share on other sites More sharing options...
slngsht Posted February 24, 2010 Share Posted February 24, 2010 Any opinions as to whether loops should be added to this frame or would the frame itself would contain a failed driveshaft? I'm wondering if I should loops them to my Caterham SV which is the same chassis except it has deDion rear suspension instead of the CSR's IRS. Edit: I talked to Ben at Caterham USA and asked if any Caterhams came with driveshaft loops. He said the only ones were R400s with sequential transmissions. Those aren't a loop like we have been talking about but rather a steel plate with a hole for the drive shaft which is riveted to the transmission tunnel. Ben said the only Caterham driveshaft failure he had heard of was a 300 hp Cosworth with a sequential transmission. It didn't have the plate or loops and the chassis tunnel contained the driveshaft. It is the shock of clutchless shifts on the sequential transmissions that cause the U-joint failures. I don't think I am too worried about a driveshaft failure on my car. Even with the quickest shifts I can manage, the sprung hub of the clutch disk will cushion the shock. I have an RX7 front U-joint and the stock Caterham rear U-joint connected by a high strength steel shaft. I mentioned MightyMike's Birkin with no chassis tubes around the transmission or driveshaft and Ben said that the Series 2 Lotus 7s were that way and in fact the live axle Birkins were direct copies of the live axle Lotus 7s. Skip, the tubes will not protect you. This is what can happen when the driveshaft lets go http://www.gt40s.com/images/jensenfailure/failure4.JPG Part of the problem is our square tubes are very thin gauge. The other problem is that when the driveshaft comes apart, the tunnel allows too much room for the driveshaft to whip around. I think it's alright to not have one, but definitely don't think that the tubes will be adequate in protecting you. Link to comment Share on other sites More sharing options...
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