Modifying the rear transaxle hoop

[Grumblebuns]

There is a TCS chassis that may be available for sale but it's for the 352 transaxle. Anyone try to modify the rear transaxle rear hoop mount for a 365; what is involved?

Joji Tokumoto 

[BDA]

The parts manual lists two hoops for the 352. One is the same as the 365 and the other has tranny mounting ears. Presumably, the one you're looking at is the latter. The parts manual lists two mounting plates (but unfortunately only shows one and it looks like it is intended for the 365 style hoop). I would bet that a 352 mounting plate could either be modified or used as a starting point for a plate to mount the 365. There would have to be accommodation made for the R/5 detent housing and cover which might complicate it a bit. On the other hand, I've never looked closely at them so it could be much harder than it I would expect. If you could get a mounting plate for the 352 only frame, if it's adaptable, it may be the easiest way to go. A new rear hoop can be welded to your frame, though. Unfortunately, I didn't keep my old 365 hoop!

My frame was for a 365 but when I put the motor and NG3 in the frame, it didn't appear that it would fit (after seeing pictures from Andy Harwood's car, I may have been hasty). A call to Richard (at Banks) resulted in a 335 hoop with mounting tubes to mate up to Richard's NG3 tranny mounts. IIRC, it was cut from a frame at the frame legs. The guy who helped me with my fabrication cut the 365 hoop out of the frame legs and welded the 335 hoop in it's place. As I remember, the fact that the 335 hoop came the way it did was helpful to my fabricator but I don't know why and that seems silly now.

[4129R]

I have both a TC and a TCS chassis separated.

The TC chassis for a 4 speed box has a V with the holes for the rear gearbox mounting plate at the top of each side of the V.

The TCS for a 5 speed box has a U shape and a different rear gearbox mounting plate.

Let me know if you need photos.

[Grumblebuns]

I just looked at the drawings in the parts manual for the different TC/TCS chassis types.The differences are pretty easy to see with regards to the mounting methods and shape of the rear hoop. It is a bit harder to determine the actual dimensions of the hoop where the tranny mounting plate bolts in.

4129R, if it's not too much trouble, I would appreciate comparison pictures between the two chassis'. If you can place a ruler showing the drop of the tubes below the attachment point on the frame and the horizontal section where the tranny attachment plate bolt in.

I'm starting to come to the conclusion that a new rear hoop for the 365 will need to be fabricated  to replace the current hoop. With any type of replacement TCS chassis' so hard to come by, this extra work may be worth the effort.   

[BDA]

If you're thinking about fabricating a rear hoop, I'd call Richard (and probably DBE and r.d.) first in case they can sell you one that you can weld (have welded) in your frame. I think that would be a lot easier. Another option is Sports Car World. I understand they are still in business (Dave @ Sports Car World (972)-620-7285).

[jbcollier]

It's not hard to fit a new loop as long as you line it up correctly.  It has to be placed exactly in the middle other wise the care will crab down the road.

[Grumblebuns]

If you're thinking about fabricating a rear hoop, I'd call Richard (and probably DBE and r.d.) first in case they can sell you one that you can weld (have welded) in your frame. I think that would be a lot easier. Another option is Sports Car World. I understand they are still in business (Dave @ Sports Car World (972)-620-7285).

Good idea BDA, I wonder why Lotus didn't use a detachable rear transmission hoop in the first place. It would have made chassis fabrication easier with only one chassis part number for the TC/TCS and separate hoops for the three transaxles.

In regards to hoop alignment, I can visualize the effect and problems of an offset placement with the entire engine/transaxle canted off a few degrees to one side. 

[4129R]

In regards to hoop alignment, I can visualize the effect and problems of an offset placement with the entire engine/transaxle canted off a few degrees to one side.

and the two arms of each rear trailing arm pointing in the wrong direction.

It would make the Europa much more like a supermarket trolley to drive !

[4129R]

Do these help?

[Grumblebuns]

Alex,

If it's not too much trouble, can you measure the the drop down distance (horizontal plane to horizontal plane) where the hoops are welded to the frame to the center point of the holes where the brackets attach. Pictures are not necessary,need only the numbers.The hoop used in the 352 looks very similar to the 336 rear hoop.

Do I see a NFL logo on the ruler used in the pictures? 

[BDA]

I'm betting the drop down distance will be the same for both hoops.

[4129R]

The tapered chassis rails to which the tube is welded are about 2 9/16" wide.
I measured the holes from the top of those rails by putting a level across side to side.

On the TC 4 speed, the centres of the holes are 200mm from the top of the rail or 7 15/16"

Those holes are for 1/2" bolts, and they are 12 1/2" apart, centre to centre.

On the TCS 5 speed, the centres of the holes are 192mm from the top of the rail, or 7 9/16"

Those holes are 12" apart, centre to centre.

Obviously the brackets bolted on the gearbox are completely different.

The ruler did have NFL logos. I have no idea where it came from. Maybe it was under a seat on one of the stripped cars.   

[Grumblebuns]

Thanks for taking the time to measure the hoops. I was also thinking that the drop down distance would be the same considering the similarity of the gearboxes with the difference mounting points made up with the brackets.