Nifty Posted March 4, 2006 Share Posted March 4, 2006 I'm assuming it is torque that is causing chassis damage like Arnie's. So what sort of torque figures are 200bhp Scholar 1.9K engines pushing out and would you consider my 1995 chassis (with removable engine bay cross members) able to handle it without modification 🤔 Do R400s have strengthened chassis 🤔 Your thoughts please   Edited to say that I intend to fit a ZF LSD too if that makes a difference to the loading on the diff mounting.  Keep off the straight and narrow 😬 Edited by - Nifty on 4 Mar 2006 07:47:59 Link to comment Share on other sites More sharing options...
Jason Plato Posted March 4, 2006 Share Posted March 4, 2006 The 1900's are pushing out between 160 - 178lb torque . I think its more than just torque thats fracturing the chassis - its also down to clutch, gearbox , flatshifting , year of chassis and tyres .  Link to comment Share on other sites More sharing options...
AMMO Posted March 4, 2006 Share Posted March 4, 2006 And doughnuts. The amount you eat and the amount you do. 😬 I have 175 ft lb of torque on my 1989 big tube De Dion. No breakages yet. I keep checking. Matt Deakin's similar vintage chassis broke with a bike engine in. Although it was prviosly fitted with a RK Crossflow I think.  Personally I will play a awiting game and see if anything goes before I do anything about it. AMMO Link to comment Share on other sites More sharing options...
Normans_Ghost Posted March 4, 2006 Share Posted March 4, 2006 My top bracket (n/s) had broken away and we did a quick mig weld fix 4 days before going to Le Mans last year. It broke away again and I stripped the rear and brazed it back on this time with an angled flat bracket brazed in across the bracket to chassis. I've refitted the diff and not tightened the top bolt so as to allow slight movement on take up. I don't do donuts and treat the car with mechanical respect, which, I suspect, makes a difference. I did notice that the chassis metal was much thinner than the bracket which needs some skill in heating the relavant metals correctly. Norman Verona, 1989 BDR 220bhp, Reg: B16BDR, Mem No 2166, the full story here You and your seven to The French Blatting Company Limited Link to comment Share on other sites More sharing options...
oldbutnotslow Posted March 4, 2006 Share Posted March 4, 2006 Ive kept saying that having a Papier-mache chassis is not a good idea Nifty despite the weight saving!! 😬 Grant Taylor OBNS Motorsport 😬 183 BHP of Black and 'Stone Chip' excitement. 😬 here Link to comment Share on other sites More sharing options...
EFA Posted March 4, 2006 Share Posted March 4, 2006 Clutches are the primary cause, flatshifting is not a problem, clucthless downshifts are a big problem. Norm, If you brazed you chassis rather than nickel bronze welded it, you may find ti a good idea to read this here I also thought they were brazed until I read this!   K2 RUM - The 7 in front of you is a DIESEL Link to comment Share on other sites More sharing options...
Support Team Shaun_E Posted March 4, 2006 Support Team Share Posted March 4, 2006 Nifty - my target power was around 200bhp but it ended up a fair bit higher (227). Peak torque is 167 lbft. I haven't had any chassis alterations so I guess I'll just keep an eye on it. My car also has removable engine bay cross members. Yellow SL #32 Link to comment Share on other sites More sharing options...
EFA Posted March 4, 2006 Share Posted March 4, 2006 Engine power is also not really the issue. Its the torque reaction through the chassis from the rear wheels when there is no drivetrain compliance due to high grip sintered clutches and sequential boxes whihc allow clutchless downshifts, as I mentioned before.  Remember the Kumschick cars had 300bhp and over 200ft/lbs, but they never broke chassis except upper diff mounts where the chassis design is just simple bad design. I have this week sourced a new (in the Caterham sense) type of proopshaft which is rubber lined between the drive and load shafts (principally like a metalastic bush) This should address the zero drivetarin complance issue but allow the advantages in terms of inertia reduction provided by small sintered clutches. I have strengthened my chassis further (in fact I have cut out the whole rear end of the tunnel and re-designed it to include 6 diff mounts - but this is to some extent academic and just an insurance against the money I am spending on cosmetic reconditioning of the chassis/body)  So if you have 227bhp amd 167lb/ft on an organic clutch of factory option dimensions, I think you will be fine. Particularly if you have the 1996 onwards chassis which has a much improved tunnel anyway. Remember, we don't hear of any R500's (and there are lots of them around) with these kinds of problems.  K2 RUM - The 7 in front of you is a DIESEL Link to comment Share on other sites More sharing options...
Big Brother Posted March 4, 2006 Share Posted March 4, 2006 Anyone know how this works (torque reaction and chassis stress) on a live axle? Am I right in thinking that the majority of the stresses caused by torque will be seen within the axle as opposed to the chassis?  Steve  SE7EN-UP! Incorporating the Caterham Links Database Link to comment Share on other sites More sharing options...
EFA Posted March 4, 2006 Share Posted March 4, 2006 Steve, On an LA axle the stressed attachment points are some distance from the axis of the turning moment, on the edges of the chassis. Therefore the torque loads on these points reduce proportionally with distance (lb(load)/ft(distance)...) The issue is that the Di Dion chassis, particularly pre 1996, is a live axle chassis converted to carry the diff. This is where and when the compromise occurred in terms of triangulation and loading. There is not that much difference between a LA and DD chassis, and much of the design was carried over with a view to supporting the diff rather than considering the loads imposed and the structural changes required to cope with this. A rudimetary effort was made in 1996 to deal with this. Not great, but a big improvement. K2 RUM - The 7 in front of you is a DIESEL Link to comment Share on other sites More sharing options...
Big Brother Posted March 4, 2006 Share Posted March 4, 2006 Thanks Arnie - read your reply, got to the bit about torque/distance and the penny dropped     Steve  SE7EN-UP! Incorporating the Caterham Links Database Link to comment Share on other sites More sharing options...
Grubbster Posted March 4, 2006 Share Posted March 4, 2006 Nifty - the ZF LSD will make a lot of difference in your case, but don't worry I'll take it off you for a donation to NTL  Roadsport build photo's here Le Mans 2004 photo's here  Edited by - Grubbster on 4 Mar 2006 14:33:32 Link to comment Share on other sites More sharing options...
Bricol Posted March 4, 2006 Share Posted March 4, 2006 Pedant alert! Torque is measured in force x distance - so lbft or lbin or Nm or mNm or mNmm etc Spring rates are measured in force / distance - so lb/in or N/mm etc Alert over. But it does bug me - even get "professionals" supplying me info at work in the wrong units . . . Easiest cure for all these chassis worries (apart from buying one of those other "sevens" ) - narrow, hard, rear tyres  Bri Link to comment Share on other sites More sharing options...
Peter Carmichael Posted March 4, 2006 Share Posted March 4, 2006 Here we go talking about engine torque without thinking about the gearing in between the flywheel and where the damage happens. In Arnie's case, the diff ratio is a contributory factor. In all cases, it is much less of an issue once you are out of 1st gear. Link to comment Share on other sites More sharing options...
Nifty Posted March 5, 2006 Author Share Posted March 5, 2006 I realise that the gearbox affects torque at the diff Peter .... however, within reason we are all running similar gear ratios anfd therefore the difference between vehicles is the torque going into the gearbox, which obvioulsy affects the torque coming out of the gearbox once the gearing factor has been accounted for. In a mathematical equation way the gearbox is a constant and can therefore be removed from both sides of the equation .. if you see what I mean  Keep off the straight and narrow 😬 Link to comment Share on other sites More sharing options...
Peter Carmichael Posted March 5, 2006 Share Posted March 5, 2006 Ah, Nifty, you're sounding like me. Link to comment Share on other sites More sharing options...
elie boone Posted March 5, 2006 Share Posted March 5, 2006 The torque loads on a LX are also damped by the shockabsorbers. The problem on a DD chassis is that the only mounting points are close to the diff itself. Myself i am not a fan of the DD, it was designed for Astons and big Merc's witch need big differentials to cope with the torque and bhp and still have a accetable level of comfort witch would be difficult with a LX on 60's roads, this is not the case in a Seven where lightness is the most important factor. It puzzels me that some people only reinforce the chassis arround the diff but i never hear of aditional bracing towards the outer tubes of the chassis witch would spread the load much more. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now