Drumster Posted October 25, 2011 Share Posted October 25, 2011 Just about to order a throttle linkage for my Jenveys TBs. What are the pros and cons of the 'over' v 'under' linkage bracket. Which would BC recommend? Link to comment Share on other sites More sharing options...
Lee Fowler Posted October 25, 2011 Share Posted October 25, 2011 Mine is over with a nice mod for the cable at the pedal box end. Lee Link to comment Share on other sites More sharing options...
GordonW Posted October 26, 2011 Share Posted October 26, 2011 I've just converted a Vx and thought and heard the Jenvey offerings were complicated (some say prone to jamming) and expensive so opted for the SBD 'push' not 'pull' idea which is both extremely simple and cheap, I used the existing cable outer with a bike cable inner, not much used yet but seems very good and apparently a similiar system has been used by others (hill climbers) in the past to good effect. Link to comment Share on other sites More sharing options...
peter clarke Posted October 26, 2011 Share Posted October 26, 2011 I had the under one and it was a real pain to fit it in. When I redid the head about 4 years back switched to an overhead system, just made a small bracket and guide and direct to the throttle body. Much easier to assemble, adjust and maintain Link to comment Share on other sites More sharing options...
TonyR Posted October 26, 2011 Share Posted October 26, 2011 I agree with Peter. I have the under linkage and it's horrible to fit, difficult to adjust. In fact it's a bit of a bodge in my opinion. Did see a nice linkage on the Duratec engine that Northampton Motorsport brought to the last L7 Curborough Sprint. Tony. Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 26, 2011 Share Posted October 26, 2011 Although I haven't used either myself, having seen Lee's I would opt for the 'over' version for the reason given by Peter. The problem with the extremely simple SBD solution is that the throttle opening, particularly at light throttle, is too abrupt and, with a very responsive engine, can make it uncomfortably jerky in traffic. The Jenvey 'star' lever on the TB has a long and a short arm but neither is optimum and the rate is very variable with throttle angle. I made up a snail cam to make the opening progressive and smooth. The result is a very docile and tractable car for about the first 20% of throttle and then all hell breaks loose 😬. The effective lever radius goes from about 60mm at closed to 35mm fully open. The Jenvey linkage is not quite as progressive but is a lot better than the simple SBD arrangement which is fine for competition but pretty harsh on the road. The throttle pedal end mod that Lee refers to was designed by Bob Simon and allows the cable to leave the pedal box at about 30deg downwards so that the cable avoids the airfilter and is not sharply bent where it comes into contact. This, again, leads to a much smoother throttle and helps prevent kangarooing at light throttle. Paul edited to correct effective radii. Edited by - Paul Deslandes on 26 Oct 2011 11:55:45 Link to comment Share on other sites More sharing options...
Mr Locust Posted October 26, 2011 Share Posted October 26, 2011 I also made a rising rate lever for my K engine to allow for better control at small throttle openings. Used in conjunction with the Auto-Tecnix cable bracket and a standard K series Caterham (Rover 25) cable routed under then over (between the TBs). Link to comment Share on other sites More sharing options...
GordonW Posted October 26, 2011 Share Posted October 26, 2011 Paul & Lee, I'm very keen on the idea of the mod at the pedal box end and seem to recall seeing a picture of one which was very well designed with a roller guide for the cable, is this the one you describe? Link to comment Share on other sites More sharing options...
Drumster Posted October 26, 2011 Author Share Posted October 26, 2011 Thanks for the responses Lee & Paul, do you have any photos or 'instructions' to do your mods? Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 26, 2011 Share Posted October 26, 2011 Yes, that's the one. It replaces the large thimble insert that acts as the cable outlet from the pedal box. The cable comes up at 30deg to the horizontal and the inner passes over a pulley, then going horizontally to the top of the pedal rod. I've had mine in the car for a couple of years and it works a treat. As I say, it was designed by Bob Simon and I have made a couple. If you blatmail me with your email address I'll email some pics. Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 26, 2011 Share Posted October 26, 2011 If you give me a couple of days I'll try to put a package of photos and sketches together, ready to email out. They are quite time consuming to make in small quantities but, with big enough demand, could be made from injection moulded nylon or glass loaded nylon. However, I'm pretty sure the tooling cost would be prohibitive. Anyone interested can blatmail their email address and I'll sent the package out when its ready. Paul Link to comment Share on other sites More sharing options...
Drumster Posted October 26, 2011 Author Share Posted October 26, 2011 Paul yhm Link to comment Share on other sites More sharing options...
Area Representative skeetsy Posted October 26, 2011 Area Representative Share Posted October 26, 2011 Hi Paul YHM Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 26, 2011 Share Posted October 26, 2011 As I've received a number of requests for info, I'm putting together a short write-up c/w with drawings and photos which should go out tomorrow. Link to comment Share on other sites More sharing options...
Bob Simon Posted October 27, 2011 Share Posted October 27, 2011 Fairlead thimble pics here. Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 27, 2011 Share Posted October 27, 2011 Hi Bob your roller thimble has been a huge success on my car and I made another one for Lee which has been fitted but he hasn't tried it yet. Maybe you should go into production! Paul Link to comment Share on other sites More sharing options...
rj Posted October 27, 2011 Share Posted October 27, 2011 I've used one of these here on the TBs Made a bracket that attaches to the cam cover and used one of these here to get the cable in the direction of the pedal box. Not very complicated and works well. Link to comment Share on other sites More sharing options...
Area Representative skeetsy Posted October 27, 2011 Area Representative Share Posted October 27, 2011 Thanks Paul I've just seen the email and it's all jolly helpful Link to comment Share on other sites More sharing options...
GordonW Posted October 29, 2011 Share Posted October 29, 2011 Paul, not sure if you have received my email? I'd like to get hold of the 'package' for the thimble roller if possible please. Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 29, 2011 Share Posted October 29, 2011 Hi Gordon. Yes I got your email and resent package. Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 29, 2011 Share Posted October 29, 2011 Sorry, trying to do this on phone as away for weekend. Suggest you check spam folder. If not there let me know and I'll have another go when I get back tomorrow evening. Paul Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 31, 2011 Share Posted October 31, 2011 I've resent to Gordon this morning to the new email and to Nick and Luke. Due to the photos the file is about 4MB so maybe its being blocked. Either that or a spam filter is stopping it for some obscure reason. If you still don't receive it I'll reduce the size of the file some more. Paul Link to comment Share on other sites More sharing options...
Bricol Posted October 31, 2011 Share Posted October 31, 2011 I used the standard Caterham cable, routed down under the air box, and up to the throttle bodies, using, I think, the standard mounting bracket secured to the air filter backplate, and a modified standard Jenvey arm with a cut- off BL throttle cable cam/cable guide welded to it. No problems with sticking or jerkiness in operation - even strangers manage to drive it with no particular care. If I remember, I'll see if I have any photos of it - can't take any on an evening as it's dark and the car lives outside. Bri Link to comment Share on other sites More sharing options...
GordonW Posted October 31, 2011 Share Posted October 31, 2011 Hi Paul, Still no sign of email, ain't technology grand....not to worry I have the pics thanks to the link from Bob, however if your notes have any dimensions to supplement my meagre workshop skills these would be appreciated. Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 31, 2011 Share Posted October 31, 2011 Gordon, I've sent you a test email to see if its the email content that's getting stuck for some reason. I assume everyone else has received it ok and aren't still waiting If all else fails I'm going to temporarily host it on a webpage for download. I'll post details shortly once its working. Paul Link to comment Share on other sites More sharing options...
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