R500 with the sequential box
Discussion
Incidentally, there are some pics from this build (including the new diff carrier stuff) here:
http://community.webshots.com/album/564624234
http://community.webshots.com/album/564624234
Mars said:
Incidentally, there are some pics from this build (including the new diff carrier stuff) here:
http://community.webshots.com/album/564624234
Interesting and dead simple. http://community.webshots.com/album/564624234
Look as though they'll certainly support the diff and reduce the twisting that causes all the problems. Might buy/make some for car actually . . .
The braces are of different lengths too and our eyes (we didn't measure) suggest to us that they are mounted to one side of the upper (seat belt anchor) rail. To the left a bit.
Given that I believe Caterham or their chassis co. uses CAD a bit more these days, I'm willing to believe there's some reasoning behind this.
IIWY I'd buy the braces from CC and just fit them yourself. They *should* fit directly to the selt belt anchor holes.
Given that I believe Caterham or their chassis co. uses CAD a bit more these days, I'm willing to believe there's some reasoning behind this.
IIWY I'd buy the braces from CC and just fit them yourself. They *should* fit directly to the selt belt anchor holes.
Mars,
The diff rotates anticlockwise (viewed from the reart of the car)under load from the engine.
Offsetting the tubes to the left will certainly counter this rotational moment, but perhaps not as effectively as if the tubes were not bushed oin the diff in the same plane as the rotational moment they are trying to counter. The unequal lengths will provide some degree of rigidity, but not as effetcive as triangulation.
The old pre 1996 chassis had the rear bulkhead constructed from 18 gauge tube. I guess this may present weld penetration isssues. In 2001 when I had the chassis break the first time (just 2 months after the sequential box was fitted) the chassis suffered a massive failure (cruciform) and 5 other cracks to tubes adjacent to the diff. Pic below shows the 4 main points where it failed. It also pulled the two upper bush stations away from the chassis. The tubes (with exception of cruciform on the tunnel top) all tore adjacent to the nickel bronze welds, and we could see from contamination of the cracks that the cruciform was tha last part of the chassis to crack.
After this the whole rear bulkhead and diff support area was rebuilt in 12 and 14 gauge tube (by Arch, not planned at the time, but this gives much more meat for the Mig welds now used on my chassis to penetrate) The connections between the tubes of the rear bulkhaed are gusseted like a spiders web and the the retainers for the upper metalastic bushes were webbed with a couple of triangular pieces of 10 gauge angle.
These two pics show that gussetting:
Above - the Spiders webs after it all broke again on 2006
Above - The upper diff mount gusset - only single ply and probably in the wrong plane - Horizontal instead of Vertical. It worked through. Damage to the chassis was then restricted to the lower mounts as can be seen below.
What we discovered however was that the lions share of the damage was on the drivers side of the chassis, and having worked out the direction of the reciproicating loads it became obvious the damage was not being done by the engine, but by the loads back up the driveline from the tyres when downshifting without the clutch.
The solution we came up with was as follows:
Triangulate the transmission tunnel to prevent any flex which could allow the rear bulkhead to move fore and aft. This included attaching the tunnel to the long scuttle lower tube just ahead of the gear lever. This first mod gave the tunnel at least the strength of a post 1996 chassis.
The issue then was to stop the torque reactions on downshifts moving the diff about. The key here was to locate the rear of the diff more securely. The standard caterham diff mounts in all non CSR and latest R500 are in a single plane of shear, so the nose and rear of the diff are not located either laterally or vertically.
This is where the solution on my car and the new R500 differ. Caterham have gone for a vertical link up to the top of the rear bulkhead. This is sadly, halfway along a pice of straight tube, so will be rather less effective than if they ran to a corner. Also, using the mount they have chosen on the diff, the bush pivoits in the same plane as the very movement we want to eliminate. The final flaw is that these two tubes are two unconnected elements. Really they need bracing together top and bottom so they cannot change their orientaion to each other. As it can all be removed at the moment, I'd think about getting someone to add this to these tubes, the only downside being some slightly elongated holes in the boot floor in order to be able to fit/remove it.
This looks like a production compromise to make a simple retrofittable solution. Perhaps there is a strong chance they had a chassis break during preprod testing, and the low cost fix to the dev car won. Guess we'll never know. It will however have a positive impact on providing control of the diffs torque reaction, particularly under engine load where it puts the two new tubes in strain if I understand they are biased towards the passenger side. Its just not executed in a good way from a pure engineering perspective.
In compression the whole thing will be rather less than perfectly rigid, so I guess we will have to wait and see if anyone gets problems..
I addressed the issue by using the two rearmost lower diff mounts, where the bushes are at a 90 deg axis to the load we are trying to control, and also ran the tubes out to the corners of the chassis and the points where the tunnel meets the lower rear bulkhead. By running all the tubes to corners or joins, I maximised rigidity through triangulation.
I hope the new R500 hangs together with the sequential box. We never got to see the clutch. With a sprung centre plate loads will be dramatically reduced, but to get the gearchange working at its optimum sub 70ms full power changes you need a small clutch.
Personally I think having a unsprung low interia clutch rated at 600ft/lbs and with the tyre sidewalls being the only compliance in the hole drivetrain, these are possibly the root causes of the issues I have.
I would be interested to see a pic of the clutch plate/cover - pref not assembled. If oit is sprung, I'd think very long and hard before moving to a proper race clutch. Perhaps this explains why the C400's all survived too.
The diff rotates anticlockwise (viewed from the reart of the car)under load from the engine.
Offsetting the tubes to the left will certainly counter this rotational moment, but perhaps not as effectively as if the tubes were not bushed oin the diff in the same plane as the rotational moment they are trying to counter. The unequal lengths will provide some degree of rigidity, but not as effetcive as triangulation.
The old pre 1996 chassis had the rear bulkhead constructed from 18 gauge tube. I guess this may present weld penetration isssues. In 2001 when I had the chassis break the first time (just 2 months after the sequential box was fitted) the chassis suffered a massive failure (cruciform) and 5 other cracks to tubes adjacent to the diff. Pic below shows the 4 main points where it failed. It also pulled the two upper bush stations away from the chassis. The tubes (with exception of cruciform on the tunnel top) all tore adjacent to the nickel bronze welds, and we could see from contamination of the cracks that the cruciform was tha last part of the chassis to crack.
After this the whole rear bulkhead and diff support area was rebuilt in 12 and 14 gauge tube (by Arch, not planned at the time, but this gives much more meat for the Mig welds now used on my chassis to penetrate) The connections between the tubes of the rear bulkhaed are gusseted like a spiders web and the the retainers for the upper metalastic bushes were webbed with a couple of triangular pieces of 10 gauge angle.
These two pics show that gussetting:
Above - the Spiders webs after it all broke again on 2006
Above - The upper diff mount gusset - only single ply and probably in the wrong plane - Horizontal instead of Vertical. It worked through. Damage to the chassis was then restricted to the lower mounts as can be seen below.
What we discovered however was that the lions share of the damage was on the drivers side of the chassis, and having worked out the direction of the reciproicating loads it became obvious the damage was not being done by the engine, but by the loads back up the driveline from the tyres when downshifting without the clutch.
The solution we came up with was as follows:
Triangulate the transmission tunnel to prevent any flex which could allow the rear bulkhead to move fore and aft. This included attaching the tunnel to the long scuttle lower tube just ahead of the gear lever. This first mod gave the tunnel at least the strength of a post 1996 chassis.
The issue then was to stop the torque reactions on downshifts moving the diff about. The key here was to locate the rear of the diff more securely. The standard caterham diff mounts in all non CSR and latest R500 are in a single plane of shear, so the nose and rear of the diff are not located either laterally or vertically.
This is where the solution on my car and the new R500 differ. Caterham have gone for a vertical link up to the top of the rear bulkhead. This is sadly, halfway along a pice of straight tube, so will be rather less effective than if they ran to a corner. Also, using the mount they have chosen on the diff, the bush pivoits in the same plane as the very movement we want to eliminate. The final flaw is that these two tubes are two unconnected elements. Really they need bracing together top and bottom so they cannot change their orientaion to each other. As it can all be removed at the moment, I'd think about getting someone to add this to these tubes, the only downside being some slightly elongated holes in the boot floor in order to be able to fit/remove it.
This looks like a production compromise to make a simple retrofittable solution. Perhaps there is a strong chance they had a chassis break during preprod testing, and the low cost fix to the dev car won. Guess we'll never know. It will however have a positive impact on providing control of the diffs torque reaction, particularly under engine load where it puts the two new tubes in strain if I understand they are biased towards the passenger side. Its just not executed in a good way from a pure engineering perspective.
In compression the whole thing will be rather less than perfectly rigid, so I guess we will have to wait and see if anyone gets problems..
I addressed the issue by using the two rearmost lower diff mounts, where the bushes are at a 90 deg axis to the load we are trying to control, and also ran the tubes out to the corners of the chassis and the points where the tunnel meets the lower rear bulkhead. By running all the tubes to corners or joins, I maximised rigidity through triangulation.
I hope the new R500 hangs together with the sequential box. We never got to see the clutch. With a sprung centre plate loads will be dramatically reduced, but to get the gearchange working at its optimum sub 70ms full power changes you need a small clutch.
Personally I think having a unsprung low interia clutch rated at 600ft/lbs and with the tyre sidewalls being the only compliance in the hole drivetrain, these are possibly the root causes of the issues I have.
I would be interested to see a pic of the clutch plate/cover - pref not assembled. If oit is sprung, I'd think very long and hard before moving to a proper race clutch. Perhaps this explains why the C400's all survived too.
Edited by Fat Arnie on Friday 12th September 00:37
Mars said:
Noger said:
The current incumbents of the L7C junta don't even like the Internet much !
Couldn't agree more. They are the reason I left the club and gave up being an AO. Since BC became popular all we ever heard at the AO meetings was how much use it was getting from non-members. They stopped short of delaring their intent to "reclaim their club" but it's exactly what they did.
ks boys.Best you take it back to your "members only forum".
Bert
I'm complaining to the moderator - this thread was almost a good discussion untill the post on the L7C
:
If you have an axe to grind go start another thread and let us continue with the good topic of diff mods
:If you have an axe to grind go start another thread and let us continue with the good topic of diff mods
Edited by Dave J on Friday 12th September 09:51
Edited by Dave J on Friday 12th September 09:52
BertBert said:
Not sure we are very interested in your L7C political bks boys.
Best you take it back to your "members only forum".
Bert
Don't read it if you're not interested. Are you one of the mods? Do you dictate what's written about on PH? No?ks boys.Best you take it back to your "members only forum".
Bert
Since I am contributing towards the R500 thread, if I choose to add additional comments I shall.
Mars said:
BertBert said:
Not sure we are very interested in your L7C political bks boys.
Best you take it back to your "members only forum".
Bert
Don't read it if you're not interested. Are you one of the mods? Do you dictate what's written about on PH? No?ks boys.Best you take it back to your "members only forum".
Bert
Since I am contributing towards the R500 thread, if I choose to add additional comments I shall.
Bert
BertBert said:
Mars said:
BertBert said:
Not sure we are very interested in your L7C political bks boys.
Best you take it back to your "members only forum".
Bert
Don't read it if you're not interested. Are you one of the mods? Do you dictate what's written about on PH? No?ks boys.Best you take it back to your "members only forum".
Bert
Since I am contributing towards the R500 thread, if I choose to add additional comments I shall.
Bert
A very interesting and worthwhile thread. Could I just ask that anyone wanting to ask unrelated questions, exchange insults or engage in inane banter with other members might consider doing so by e-mail rather than seeking to display their razor sharp wit in public. We really have no interest.
Dave J said:
Mars
Is the clutch conventiobal AP sprung item on the new '500
ps - about time we met in Hopwood isnt it
Don't know yet Dave. The engine hasn't yet been delivered. I think it's due next week, but Nige hasn't chased it as he's got enough to be getting on with for a couple of weeks yet.Is the clutch conventiobal AP sprung item on the new '500
ps - about time we met in Hopwood isnt it
They used to deliver the clutch already attached to the engine. I suppose it'll be the same.
I have to admit that I quite like the standard AP clutch. I know it's not rated for the sorts of power this engine can put out but my engine was only a little less powerful, and had about the same torque, and yet that clutch was faultless. Those people who tried uprated paddle clutches (Rob G was one such person, I think) found them not to their taste and reverted back to the AP one.
We can say that the new clutch will be hydraulically actuated though. There's a reservoir for such above the pedal box.
There's no bellhousing yet either. Incidentally, I always thought having the dry sump tank being in the bellhousing was a great idea and I was a little disappointed to find they have done away with that idea in favour of a conventional tank behind the cruciform.
I'm not working at the mo Dave, so if you fancy a 5 mile diversion from Hopwood, you'd be welcome for a cuppa in Redditch.
Mars,
What would be really useful would be (when its delivered) a weight for the flywheel and clutch assy. Does the R500 use the std Duratec crank or an aftermarket steel item? If the latter, anyone got any pics or know if it has a reduced number of counterweights, x drilled b/e journals etc??
There is a concensus the clutch is the achilles heal of my car. Failures are not unique to the chassis. From being told by Mr Tewson at SuperClutch that it explicitly required hydraulic actuation, a concentric type, supplied by him which failed regularly, with teh engine out and a new slave assy at £200 aboiut 4 times. I then moved to an external slave system like the LHD SV which retains the lever in the bell housing. With this the control rod would sheer with alarming regularity, so it was retired to the bin.
Since April I've gone for cable actuation just like my car had with its GM clutch. Pedal feel is fine with the 5.5" unit, and clutch reliability has been 100% since.
Compliance with a sprung centre plate may save the R500 a lot of undue stress. I guess we need to wait and ssee. Is this the type of clutch used in the C400s with the seq box?
The big problem is the weight and rotational masses a clutch and flywheel of this type incur. It does not allow the rapidity of change which is certainly the whole value proposition of a sequential box in the first place.
Pics please!
What would be really useful would be (when its delivered) a weight for the flywheel and clutch assy. Does the R500 use the std Duratec crank or an aftermarket steel item? If the latter, anyone got any pics or know if it has a reduced number of counterweights, x drilled b/e journals etc??
There is a concensus the clutch is the achilles heal of my car. Failures are not unique to the chassis. From being told by Mr Tewson at SuperClutch that it explicitly required hydraulic actuation, a concentric type, supplied by him which failed regularly, with teh engine out and a new slave assy at £200 aboiut 4 times. I then moved to an external slave system like the LHD SV which retains the lever in the bell housing. With this the control rod would sheer with alarming regularity, so it was retired to the bin.
Since April I've gone for cable actuation just like my car had with its GM clutch. Pedal feel is fine with the 5.5" unit, and clutch reliability has been 100% since.
Compliance with a sprung centre plate may save the R500 a lot of undue stress. I guess we need to wait and ssee. Is this the type of clutch used in the C400s with the seq box?
The big problem is the weight and rotational masses a clutch and flywheel of this type incur. It does not allow the rapidity of change which is certainly the whole value proposition of a sequential box in the first place.
Pics please!
Fat Arnie said:
Mars,
What would be really useful would be (when its delivered) a weight for the flywheel and clutch assy.
Unfortunately they are very likely to be attached to the engine, and I'm certain Nige won't want to separate them.What would be really useful would be (when its delivered) a weight for the flywheel and clutch assy.
If they come separate, I'll take my kitchen scales round.
I'll take pics of course.
Fat Arnie said:
Does the R500 use the std Duratec crank or an aftermarket steel item? If the latter, anyone got any pics or know if it has a reduced number of counterweights, x drilled b/e journals etc??
I've no idea. Some of the Se7ens list guys (particularly Rob G) might know. Rob has a pretty smart Duratec installation from Ammo in his nice-and-recently-rebuilt motor.Fat Arnie said:
There is a concensus the clutch is the achilles heal of my car.
I've seen the pics of your set up and it looks quite brutal. I'm sure Rob mentioned his paddle clutch was a bit sharp, which is why he decided to revert to the original AP clutch.Fat Arnie said:
Failures are not unique to the chassis. From being told by Mr Tewson at SuperClutch that it explicitly required hydraulic actuation, a concentric type, supplied by him which failed regularly, with teh engine out and a new slave assy at £200 aboiut 4 times. I then moved to an external slave system like the LHD SV which retains the lever in the bell housing. With this the control rod would sheer with alarming regularity, so it was retired to the bin.
Since April I've gone for cable actuation just like my car had with its GM clutch. Pedal feel is fine with the 5.5" unit, and clutch reliability has been 100% since.
Well, as you know, most Caterhams have cable actuation which works well. Concentric hydraulic clutches may be technically better as they push the CRB perfectly [searching for the correct term and failing] "in-line", but some of the problems the earlier Vx concentric clutches suffered from makes one think twice before entertaining the idea. It's not a quick fix to remove a slave cylinder as I'm sure you appreciate more than most.Since April I've gone for cable actuation just like my car had with its GM clutch. Pedal feel is fine with the 5.5" unit, and clutch reliability has been 100% since.
Fat Arnie said:
Compliance with a sprung centre plate may save the R500 a lot of undue stress.
You know, I reckon that's what made the original SLR such an easy car to drive. It just worked. The tech specs suggested even that level of performance was close to the ceiling for that clutch but I haven't heard of any failures.After 4 years and a good 15K+ miles in V7SLR, I took my clutch out for my latest DVA upgrades and bought a new one "just because"... but after installing the new one, another local chap (Myles) came over and measured my old plate (which I'd not looked at since removing it) against the new one and found less than 15% wear. We put the old one in his car, which I believe he's still using.
Fat Arnie said:
I guess we need to wait and see. Is this the type of clutch used in the C400s with the seq box?
Honestly I've no idea. As you may know, I've been away from Se7ens for a while (had a Cerbera in the intervening period). Nige's new R500 is the first time I've had any real hands-on dealings with Se7ens since the end of 1995.Fat Arnie said:
The big problem is the weight and rotational masses a clutch and flywheel of this type incur. It does not allow the rapidity of change which is certainly the whole value proposition of a sequential box in the first place.
I couldn't agree more. To be honest *any* gear-change is made faster with reduced inertia in the rotating masses. I've always hated manual BMWs for this reason. The Cerbera was a revelation - the flywheel on the AJP-V8 must be made of cardboard..!!But you're right, for a sequential box the lack of rotational mass is essential, or the point of the box becomes lost.
Fat Arnie said:
Pics please!
I'll be popping over there from time to time but Nige is updating his own Webshots diary as he goes along. I probably won't get over there until next week now, but I don't think the engine's due until then anyway. I would certainly like to see the engine before it goes in. Having said that, Nige and I are members of the Worcs "engine in" crowd, having done quite a few over the years, so I'll be present before it goes in no matter what. 
Std crank in the r500
in the C400 race regs it is suggested that the clutch has a 20 hour life.
I understand that the C400 race cars use a std ap sprung clutch ( was asking the racers this very question at castle combe the other month)
A prop broke at combe on one of the C400's on seqeuntial- but this was said to be the second one to go and a "life" issue.
Several of the C400 race guys said that the sequential was no quicker and they used the clutch on the way down the box.
The other problem reported was the big ends/ rod interface adding additional crankcase ventilation, as a result the dry sump tank was increased in volume to a 7L (?) item and a new sump pan design was in use - possibly pace ? .
Finally a new ventilated nose cone was in action with a scoop into the top of the nose where the badge would normally live and a exit at the rear of the nose cone near the bonnet .
Drivers were complaining of excessive footwell temps .
I showed them my foil/bubble/foil footwell insulation
that keeps my feet loverly and cool.
in the C400 race regs it is suggested that the clutch has a 20 hour life.
I understand that the C400 race cars use a std ap sprung clutch ( was asking the racers this very question at castle combe the other month)
A prop broke at combe on one of the C400's on seqeuntial- but this was said to be the second one to go and a "life" issue.
Several of the C400 race guys said that the sequential was no quicker and they used the clutch on the way down the box.
The other problem reported was the big ends/ rod interface adding additional crankcase ventilation, as a result the dry sump tank was increased in volume to a 7L (?) item and a new sump pan design was in use - possibly pace ? .
Finally a new ventilated nose cone was in action with a scoop into the top of the nose where the badge would normally live and a exit at the rear of the nose cone near the bonnet .
Drivers were complaining of excessive footwell temps .
I showed them my foil/bubble/foil footwell insulation
that keeps my feet loverly and cool. Gassing Station | Caterham | Top of Page | What's New | My Stuff