Lotus Elan

Twin-Cam to T5 Bellhousing Anyone?

PostPost by: johnc » Thu Jan 24, 2008 4:18 pm

I appreciate the comparison you guys put together -- it should help provide a focus for discussion and resolution.

I personally have never done any sand casting, but I am not convinced it should be deemed too expensive at this point. Perhaps this site, or a similar cost estimating site, can help resolve this question http://www.custompartnet.com/. I played around with sand casting for 5 minutes and was able to get a result. The program appears to be quite sophisticated and I assume able to give a reasonable result after one spends the time to learn the system. I also assume that we could hackup and reshape an existing bellhousing for a pattern at virtually no cost compared to outside tooling cost.

custompartnet.com also has the capability of estimating machining and other costs. So perhaps it might be helpful for estimating the cost of reworking an input shaft, etc.

Have fun.
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PostPost by: gjz30075 » Thu Jan 24, 2008 5:38 pm

CBUEB1771 wrote:
gjz30075 wrote:From what I'm reading here, I'm beginning to like using the stock bellhousing, too, but why use an adapter plate? That pushes the shifter location back. Why not simply re-drill the bellhousing for the trans mountings?

Greg Z


The primary reason is that the input shaft for the T-5 is roughly 3/4" longer than the input shaft for the Elan 4-speed box. As an alternative we are looking into a shorter input shaft but that has not yet been resolved. There is also a distinct possibility that the lower attachment points for the T-5 are so low compared to those on the Elan box that we would be drilling into air. .


I understand the need for a shorter input shaft so if Moderndriveline is turning down the diameter, I can't see it being a big deal to simply make it shorter at the same time. But I do see the concern about the lower mounting points of the box being perhaps too low. Good point.

This is all good stuff and the most progress this group has made, collectively, for 5 speed information.
Thanks guys,

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PostPost by: CBUEB1771 » Thu Jan 24, 2008 6:45 pm

gjz30075 wrote:I understand the need for a shorter input shaft so if Moderndriveline is turning down the diameter, I can't see it being a big deal to simply make it shorter at the same time.


About 3/4" needs to be trimmed from the pilot spigot, then the splined section also needs to be relieved to the pilot diameter over a similar length so it won't jam into the back of the crank. Then we'll find out if the remaining spline is long enough to engage the friction disc hub correctly with enough end float for clean clutch actuation. If not we'll need to get the splines cut or broached deeper (axially). Then the input shaft bearing retainer needs to be shortened. Then we'll see if there is enough axial room left for the annular slave cylinder and release bearing. I don't mean to sound like a s**t :) , it is just one of those cascading events. We are looking at all of these issues. The goal is to design/identify the cheapest and easiest solution consistent with good and reliable performance. We are having fun, just a lot of carpets to peek under.
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PostPost by: gjz30075 » Thu Jan 24, 2008 7:56 pm

Got it. The adapter plate is sounding like a better idea. Moving the shifter to the appropiate location shouldn't be too big of a deal. I've got an early Mustang in which I put the T5 in. The shifter stub has two threaded holes and I moved my shifter back by making a plate with two holes to match the shifter stub and two more holes at the other end of the plate to bolt the stick to. The plate can be made of any desired length for positioning the stick. If the shifter and its stub doesn't stick too far up into the cabin, this solution should be workable.
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PostPost by: johnc » Tue Jan 29, 2008 9:54 pm

Photo comparison of stock Elan and Ford-2.3L-T5 bellhousings.
Attachments
P1010046.JPG and
Elan
P1010047.JPG and
Elan
P1010050.JPG and
Elan Bellhousing Plate
P1010044.JPG and
Ford 2.3L T5
P1010045.JPG and
Ford 2.3L T5
P1010048.JPG and
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PostPost by: TomR » Tue Jan 29, 2008 11:53 pm

Yep, you can see that the top two bolt holes are in the wrong place as illustrated in my picture thread, but the others are good.

Did you check the length of the two housings relative to exposed input shaft length? The bellhousing should make up the 3/4" difference mentioned earlier as both shafts have to end up at the end of their respective cranks which are similar I think. I agree that the Ford pilot has to be turned down from 0.68 to 0.59. I think Camaro shafts are 0.59 to start with but the Ford spline works with the 2.3L 8.5" clutch plates. I think the Merkur input shaft is different from the others - maybe it is the longer one and has a different bellhousing?

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PostPost by: johnc » Thu Jan 31, 2008 11:39 pm

It has been mentioned that the T5 input shaft has to be turned down to 0.570" to fit the pilot bearing. The pilot section of my OE S1 Elan transmission measures approx 0.672". So I checked Dave Beans catalog and found four pilot bearings listed -- two for the 4-bolt, and three for the 6-bolt crankshaft.

4-bolt crank -- 0.670 & 0.570, both oilite bronze
6-bolt crank -- 0.670 & 0.590, two oilite, and one 0.590 needle roller.

In conclusion, a 0.590" pilot works for all Elans but you may have to change your pilot bearing.
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PostPost by: johnc » Fri Feb 01, 2008 12:01 am

In my previous message I stated the conclusion incorrectly. Only the 0.670 pilot bearing is common to all Elans.
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PostPost by: johnc » Fri Feb 01, 2008 7:40 pm

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.
Attachments
appEngForm.gif
Tremec application form.
appEngForm.gif (7.79 KiB) Viewed 2531 times
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PostPost by: msd1107 » Fri Feb 01, 2008 9:13 pm

Merkur XR4ti with gearstick and bell - 81 lbs.

Dimensions - the gearbox is in my garage and the tools are elsewhere, so the dimensions are approximate.

A ... 21 1/2"
B ... 7 3/4"
C ... ~1 3/8"
D ... ~ 4"
E ... 23 1/4"
F ... 14 1/2"
G ... not taken
H ... 4 1/8"

Input shaft dia ... not taken
Input shaft spline count ... 23

Output shaft spline diameter ... ~ 7/8"
Output shaft spline count ... 25
Output shaft exposed length ... 3/8"

Bellhousing depth front to rear face ... 7 3/4"

Trans w bell front face to shift lever ... 29 1/4"

Remember, on an Elan the gearstick on later cars is offset to the rear and leans backward so the shift knob is 3 odd inches further to the rear than dimension A.

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PostPost by: CBUEB1771 » Fri Feb 01, 2008 9:48 pm

johnc wrote:So I checked Dave Beans catalog and found four pilot bearings listed -- two for the 4-bolt, and three for the 6-bolt crankshaft.


John,
Thanks for checking Bean's catalog, something I should have done some time ago. You have proven that we don't have to worry about reducing the pilot spigot diameter on a T-5, it is just a matter of buying the correct pilot bushing. BTW, there appears to be a typo in Bean's catalog. They give the input diameter for 036E 6006 as 0.570" (15mm). Well, 15 mm is 0.590", so 0.570" is likely a mistake, not a true size option. I knew there were changes in the input shaft configuration over the life of the Elan but I did not realize there were two pilot diameters, 0.670" and 0.590". The T-5 is available in the same two pilot diameters depending on the application.
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PostPost by: johnc » Thu Feb 07, 2008 5:26 am

A little update. I got lucky and was able to source a 1987 2.4L T5 with bellhousing, shifter and output shaft yoke on craigslist for pick-n-pull pricing. I should be able to post dimensional data in day or two.

My first impression is that with a modified Mustang tail housing we should be able locate the shifter somewhat forward from that provided by the S10 tail housing by using a design similar to that used by Spyder Engineering in their MT-75 conversion (see attached picture). To see this picture in context goto: http://www.spydercars.co.uk/practical_performance_car_21st_century_elan_feb05_pg4.htm

Does anyone have any thoughts on this shifter design -- either pro or con?
Attachments
feb05_pg4_image_17.jpg and
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PostPost by: johnc » Sat Feb 09, 2008 11:30 pm

Below is a picture of the T5 transmission with 3 marks along the tail housing casting. The center mark labled 'Elan' is approximate center of Elan gearshift opening assuming a stock Elan bellhousing and no adapter plate.

The front mark is represents the approximate location of the Elan gearshift opening assuming a Mustang 2.3L bellhousing and no adapter plate. It is located 3/4" forward of the center mark.

The rear mark labeled 'S10' is the location is the S10 shift lever location again assuming a stock Elan bellhousing and no adapter plate. It is located 1" and 1 3/4" behind the center of the Elan gear shift opening with an Elan and Mustang 2.3L bellhousing respectively.

The S10 shift level location is assumed to be located 298.2 mm (11.74") from the transmission front face.

In my previous post I indicated it might be possible to move the shifter forward of the S-10 location. Well it is not as straight forward as I originally imagined. There is no bushing where the shifter shaft exits the case cover, and the diameter of the shifter shaft in this area is reduced compared to where it is supported by bushings. The rear bushing is located just forward of the shifter box.

Also on second thought I am puzzled on how the Spyder MT-75 shifter works. Assuming the MT-75 uses a single shift rod like the T5 I don't see how the Spyder design is able to rotate the shift rod either CCW or CW to select either 1st and 2nd, or 5th and R.

If anyone wants specific T5 pictures, now is a good time to ask. Removing the tail housing and cover plate is no problem.
Attachments
P1010008-2.JPG and
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PostPost by: garyeanderson » Sun Feb 10, 2008 1:36 am

Hi John

What is the max width of the T5 at the rear of the main case where it mates with the tailshaft housing. This will be a critical dimention on the Spyder chassis as the fattest part of the tailhousing need to pass through the two vertical square tubes, I measured 7 3/8 inches between them.

Thanks Gary
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PostPost by: johnc » Sun Feb 10, 2008 3:33 am

Gary, at the rear of the main case there is a tab on each side which can be eliminated so I will ignore them. I measure 4" from the center line to each side for a total width of 8". The measurement was made with the tail housing on. A measurement with the tail housing off should be more accurate, but I wouldn't expect it to change very much.
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