Lotus Elan

Gearbox dimensions

PostPost by: worzel » Thu Aug 04, 2011 1:53 pm

Hi

Many apologies for asking this again- but I've lost the info. Before I lose my marbles can anybody supply the following tech details.

I need these measurements to confirm in advance the clutch will work- I don't have ready access to an engine/gearbox combo already out of a car.

Distance from the end of the input shaft (on a 4 speed box) to where the splined section begins.

Distance from the end of the input shaft to where the splines end (ie the overall length of the splined section)

Distance from the front face of the gearbox to where the splines begin or- distance from the end of the input shaft to the face of the box where the bellhousing mounts.

Regards and many thanks

John
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PostPost by: john.p.clegg » Thu Aug 04, 2011 4:19 pm

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PostPost by: worzel » Thu Jan 05, 2012 10:53 am

Hi John

Thanks for the link.

Based on that info I've come up with the following measurements for the input shaft of the std 4 speed box-

From the front face of the gearbox casing the input shaft protrudes 160mm in total.

The distance from the front of the box to the beginning of the splines is 85mm.

The length of the splined section is 43mm

From the forwardmost part of the splines to the end of the nose is 32mm.

Are my calculations correct- if so I reckon from other measurements that the flywheel face sits 66mm proud of the engine block so that with everything bolted up (and assuming a std clutch assembly) the beginning of the splines of the friction plate (ie facing towards the gearbox) must be sitting right at the beginning of the splines of the input shaft. Do you reckon my line of reasoning is correct? Why the fuss- well I'm getting conflicting info on whether or not a box with a different input shaft will work since the splines on that box are positioned differently eg on a Type 9 the friction plate splines would sit roughly halfway along the input shaft splined section and end up nearer the nose of the shaft.

Regards

John
the gearbox end) must be located
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PostPost by: bcmc33 » Thu Jan 05, 2012 2:19 pm

worzel wrote:-
From the front face of the gearbox casing the input shaft protrudes 160mm in total.

The outside length of the bell housing is 171.5mm

worzel wrote:-The distance from the front of the box to the beginning of the splines is 85mm.

I make it 87.5mm to the end of the retainer tube. There is probably some spline inside the tube.

worzel wrote:-The length of the splined section is 43mm

Agreed 43mm

worzel wrote:-From the forwardmost part of the splines to the end of the nose is 32mm.

I make it 33mm
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PostPost by: garyeanderson » Thu Jan 05, 2012 2:28 pm

elan-f14/twin-cam-bellhousing-anyone-t15954-45.html
maybe start at the beginning and get some more info.

:(
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bell length.JPG and
Last edited by Guest on Thu Jan 05, 2012 3:50 pm, edited 1 time in total.
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PostPost by: worzel » Thu Jan 05, 2012 3:23 pm

Hi to all

This is for Brian- re your slightly differing dimensions- you aren't by any chance taking your figures from a 5 speed two seater are you?- inputs from other owners indicate that the overall length (outside edge to outside edge) of the 4 speed cast iron bellhousing is 160mm give or take one or two mm.

Regards

John
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PostPost by: bcmc33 » Thu Jan 05, 2012 5:04 pm

worzel wrote:Hi to all

This is for Brian- re your slightly differing dimensions- you aren't by any chance taking your figures from a 5 speed two seater are you?- inputs from other owners indicate that the overall length (outside edge to outside edge) of the 4 speed cast iron bellhousing is 160mm give or take one or two mm.

Regards

John

John,

If you want to be precise, the overall size of my 4 speed bellhousing is 6.3/4".

The other dimension I took is the spigot end face to the front face at 7.94mm (5/16").

As I see it, if the bellhousing was 160mm the spigot would be proud of the front face by 3.5mm and would not be a good match to the crank.
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PostPost by: worzel » Fri Jan 06, 2012 12:34 pm

Hi- and thanks to all for taking the trouble to reply.

I just need two last pieces of information-

1) On a std block with a std flywheel fitted how far from the block is the face of the flywheel- ie the face against which the friction plate bears?

Not an idle enquiry just for the sake of it- I'm trying to figure out what the consequences might be of fitting a spacer plate between the bellhousing and the engine so as to move the gearlever position a short amount. In effect I'm tyrying to figure out exactly where the splines of the friction plate would sit on the input shaft.

2) As for the friction plate how long is the splined section and how is it biased, ie how much protrudes on the gearbox side and how much on the engine side?

Many thanks.

John
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PostPost by: garyeanderson » Fri Jan 06, 2012 12:55 pm

piss-ant wrote:http://www.lotuselan.net/forums/elan-f14/twin-cam-bellhousing-anyone-t15954-45.html
maybe start at the beginning and get some more info.

:(


John

Did you read this ? what is it that this info won't help you. You know how I love reruns - when do the 3 Stooges come on :)

johnc wrote:The following measurements were taken from a stock S1 Elan 4-speed transmission and bellhousing.

Stock Lotus Elan Transmission:

A = 10 3/4?
B = 6.420?
C = 1.198?
D = 3.340?
E = 24 5/16?
F = 11 7/16?
G = 3.850?
H = 2 3/16?

Input Shaft Pilot Diameter = 0.670?
Input Shaft Spline Count = 20
Input Shaft Spline Outside Diameter = 0.870?
Input Shaft Spline Inside Diameter = 0.770?

Output Shaft Spline Diameter = slight taper to 0.870?
Output Shaft Spline Count = 20
Output Shaft Exposed Length = 0.790?

Bellhousing:

Depth (front to rear face) = 6 3/4?

Transmission With Bellhousing Attached:

Front Face to Shift Lever = 17 1/2?

Input shaft to bellhousing face 0.310? (tip of shaft is recessed behind front face of bellhousing)

If you can supply the corresponding transmission and/or bellhousing dimensions from say a T5, T9, Isuzu, Alpha Romeo, please do -- this type of information is very hard to come by and would help the 5-speed effort.


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PostPost by: worzel » Fri Jan 06, 2012 7:29 pm

Hi

That's a very useful drawing- particularly confirmation about the bellhousing depth but I can't see anything indicated on it that shows how away from the engine block is the outer face of the flywheel. As I said if I know this latter measurement I can figure out just where the friction disc sits on the splines of the input shaft.

Anybody out there just happen to have a spare engine lying around for these measurements?

I think the clutch disc has a splined length of about 1.25 inches- anybody able to confirm that and also tell me how the two sides are biased- ie how much splined section sits proud of the friction material on each side- unfortunately I don't have a disc to hand to check this point.

Regards

John
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PostPost by: garyeanderson » Fri Jan 06, 2012 8:11 pm

Hi John

do these work for you

Gary
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input shaft.JPG and
flywheel face to block.JPG and
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PostPost by: bcmc33 » Fri Jan 06, 2012 8:24 pm

worzel wrote:Hi

That's a very useful drawing- particularly confirmation about the bellhousing depth but I can't see anything indicated on it that shows how away from the engine block is the outer face of the flywheel.

From my notes the distance is 54mm.
I also note that it is 30mm from the block to the end of the crank where the flywheel sits.
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PostPost by: worzel » Sat Jan 07, 2012 1:48 pm

Hi Gary

Thanks for the pictures- now you have me worried.

Have a look at the drawing I've posted-

A represents the gearbox case face and B the rear face of the block. I've taken an average distance between them of 170mm to allow for slight manufacturingtolerances in the casting.
The numbers 85/43/32 represent the dimensions of the std 4 speed box input shaft.
Distance C represents the outer face of the flywheel against which the clutch friction disc sits.

Here's my problem-(I think)-the distance from the box to the flywheel outer face must be 116mm (170 - 54) so that means the friction disc sits 31mm along the shaft splines (85 + 31). This leaves only 12mm of spline within the flywheel. Now from memory (I don't have a clutch disc to hand) I'm sure that the centre splines on the clutch disc protrude far more than 12mm towards the engine so does this mean that the splines of the disc "hang over" the input shaft splines within the flywheel?. With my original measurements (can't recall from where I got them) of 66mm for block to flywheel face it makes more sense- but I can't argue with your pictures for measurements
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DSC00534.JPG and
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PostPost by: garyeanderson » Sat Jan 07, 2012 3:09 pm

I think that the measurements may be causing some problems

6.75 is the gearbox face to the bell mouth face
there is also a closing plate that is .0625 so that the max which is 6 13/16 or 173.0375 mm
Gearbox face to engine rear face.
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input shaft with line.JPG and
input shaft with clutch inserteda .JPG and
input shaft with clutch inserted .JPG and
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PostPost by: worzel » Sat Jan 07, 2012 4:00 pm

Hi Gary

Thanks again for your quick reply. Just to clarify- in the bottom picture of the last 3 you included, and assuming 54mm is the distance to the flywheel outer face the distance from the outer flywheel face to the mounting face for the input shaft looks to be about 110mm on your picture (can't be certain because of the slight angle) and on one of the other pictures you show the splines protruding thru the friction plate for around 12mm or so.

Adding the 3 numbers gives 176mm but I'm assuming that in practice the guide sleeve for the bearing carrier doesn't actually but right up to the splines of the disc anyway so the figures look ok.

Why all of this palaver you may ask?- well I'm going to use a Rocket to BDA bellhousing mated to a 5 speed MCT75 box. This bellhousing however is 175-6 mm deep which as you've probably figured alters the positioning of the input shaft splines on the friction plate splines. I was concerned that it might result in the disc splines "overhanging" those on the input shaft but it looks like I'm fretting over nothing.

John
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