Caterham 7 with transaxle

[edmandsd]

Has anyone ever built a 7 with a transaxle arrangement ? A l/weight sequential Hewland box would easily fit in the back of a Caterham allowing the engine to be fitted further back and saving a lot of weight.

[Paul Ranson]

I don't think 'easily fit'....

 

The gear bit would interfere with the de Dion, so you'd have to rearrange that. The fuel tank would probably also interfere, and you wouldn't be able to get it to bits to change the ratios, and that's half the point...

 

Anyway why do you want to move the engine back?

 

Paul

[Chelspeed]

The westf1eld FW400 has (had?) one, as well as a carbon composite chassis. Nice.

[Peter Carmichael]

No Paul, Dave doesn't have an issue with it clashing with the de Dion tube because he is intending the world's first *live transaxle*... (just to get the unsprung mass up) teeth.gif

[cdg]

Dave,

 

You're always second guessing my ideas!

 

The transaxle you need is the Alfa Romeo 75/Alfetta/GTV one. The whole drivetrain including clutch housing is one (splittable) unit, and the output shafts are at the extreme rear of the housing. You would need to make a flange to fit to your crank (machine down an old flywheel)and then a propshaft to the rear mounted clutch spider. It isn't as light as a Hewland,48kg as opposed to 34kg, but has good ratios, and the 3litre V6 clutch can take monster torque as it's a twin plate affair.

 

I wouldn't attempt to put anything more than 200bhp through an LD200, Mk9 etc. The FT200 is strong but rare, and very expensive at £4000 ish used. The Alfa V6 transaxle can be bought used for £100! I have an Alfetta trans. sitting in my garage as I was going to use it in the Mallock and go IRS, but I have something much more outrageous planned...

 

I'd say "bollocks" to what people think and do it!

 

Chris.

 

Edited by - cdg on 25 Mar 2002 18:22:45

[oilyhands]

I have some photos somewhere of an early Lotus seven from Brazil or Venezuela which has a transaxle fitted, cant remember where the TX is from but the installation looks pretty good.

 

Oiuly

[edmandsd]

Thanks Chris - I/HT Racing were thinking of using an FT200 with the current live chassis......and yes I was being serious.

Ray Addis at HT Racing who used to be involoved in Australian Touring Car racing a few years back is currently designing/fabricating a lightweight wide track equal length/plane double wishbone set up for the car, using modified trunnions and with provision for a front anti roll bar (although I won't be using one), which goes to show I'm prepared to put my/their ideas into practice.

[James Arnold]

Whilst I haven't done any measurement I'b be surprised if the Alfa gearbox would fit - the diameter of the clutch house would be too big and right by your elbow.

I can also say, owning a 75 and previously a GTV6, that this gear box is not one I am over fond of. In the GTV with the 'old' linkage it was nasty in the extream. In the 75 its tolerable but way behind the norm.

The GTV6 had the twin plate clutch (but I thought 3.0litre 75 had a single?) and it was a nasty brute.

I know of a few GTV6s that were converted to a ford g/box.

Speaking as a keen Alfa man, the alfetta gearbox is possibly the worst bit!

J

 

[Paul Ranson]

It's my understanding that the weak point of the LD200 is the CWP, and that the FT200 is pretty much the same in this area albeit with bigger (and heavier....) gears.

 

These transaxles are all designed to be structural and take suspension loads, so perhaps that's a way forward for the Caterham chassis to get a true IRS?

 

Paul

[cdg]

The Alfa transaxle would have been a "budget" fitment. I suppose everything depends on how much one is willing to spend, and how much one is willing to modify the chassis. The Alfa clutch housing is about 290mm in dia. but it can be offset to the passenger side on a pure competition car. You could have a direct gear-change mechanism and so get rid of the admittedly troublesome Alfa gear linkage.

 

Obviously the Hewland transaxle is the one of choice if money is no object. Adapter plates and input shafts can be made for any application, and the facility of being able to quickly change ratios is extremely useful.

 

You could be forgiven for thinking why not just buy a purpose built Sports Racing Car? ... as modifying a road Caterham to that extent is at best a compromise.

[edmandsd]

What are you planning Chris, sounds different/exciting ?

[R2D2]

The Porsche 924 uses a transaxle in the rear of the car. I think that it uses an Audi gear set and there used to be a close ratio set and a ZF sticky available.

 

I am sure that the prototype RS1700T Rally Car (Escort replacement that was shelved when the Quattro appeared)tested with one before the special Hewland was finished. This unit is quite compact compared to the Alfa and quite a lot lighter.

 

The configuration of Front Engine, Rear Transaxle and a De Dion was used on quite a few successful F1 Ferraris and Maseratis. The Lancia Aurelia uses the same set up and the handling is a delight.

[cdg]

Chris,

 

I'd thought of the 924, but it requires a hefty torque tube to take the prop via a central bearing as the gearbox input shaft doesn't like too much lateral thrust. The Alfa clutch housing carries hefty bearings, and all it requires is a prop flange/universal joint mated to the clutch spider. Now if you were to make an adapter between the Porsche transaxle and the Alfa clutch housing...

 

Chris.

[elie boone]

The best clutch for the alfa transaxle is the one from the turbo. A lot of V6's are converted to the turbo single clutch system and this seems to work better. If you want to be 100% sure maybe it is best to contact the Alfa owners club.

Why not consider the Porshe ( 6 speed )or Quaife transaxle, the gearbox will be at the end of the car but this way you keep everything in the centerline of the car ( easy'er to balance than an offset set up )and it is easy'er to modify the chassis to IRS and no need to use that dinosaur of a dedion axle. wink.gif

With this setup you can use two fuel tanks or a saddle tank.

[R2D2]

I looked at building a Mk3 Escort as a rally car a few years ago using a V6 Alfa in the front and a 924 Transaxle. (The wheelbase on the Escort and the 924 are within 0.5" and the track is similar)

 

I am fairly sure that the 924 transxale used to be used in the back of an 80 Quattro.

 

I think that a flexible disc coupling would be the best way to connect the transaxle to the engine as this would be quite light.

 

The problem will be the load on the input bearing to the transaxle and the position of the weight, so I agree that a Hooke Joint would be quite heavy and a long way out.

 

The lateral critical speed of the shaft would need looking at as well depending on the final length of the transmission shaft.

 

The calcs aren't very difficult and although flexible disc couplings are expensive compared to Carden shafts they are much lighter and may get rid of the need for the torque tube.