Lotus Elan

5 speed T9 conversions

PostPost by: worzel » Sat Oct 02, 2010 10:03 am

Hi

See my other post today- this one might specifically interest those with T9 boxes already in their cars.

At last I've got back a couple of parts I was having made by my local precision engineer.

Basically I've designed a system that reintroduces the spring loaded bias against 5th gear. An earlier version fitted in a boxed sextion on the top of the lid. That worked very well but some might have considered it bulky.

This one screws into the lid and is about an inch round and about 1.5 inches high.

I'll stand corrected on the last point but my understanding of the Alan Voights system (which also screws into the lid) is that a ramp/cam effect acts as limit on sideways lever travel in the neutral plane.

To obtain reverse one pushes the lever hard over leftwards to overcome the spring loaded ramp which is effectively a cut out in the interlock disc in the main casing. Selection of 5th operates in a similar fashion ie you have to overcome a stepped resistance.

I know this idea works because I have something similar in my own converted car. The problem (if that's what it is) might arise when changing from 5th to 4th. Pulling the lever out of 5th one needs to manually pull the lever leftwards to overcome the ramp/cam which usually leads in turn to having to move the lever back to the right to find 4th or 3rd.

You do get used to it but I think a spring system without a ramp is better. My idea does this and has the advantage of being adjustable for resistance by substituting springs of different rates. The cam effect is retained for selection of reverse but this is no bad thing since selecting reverse is only done when stationary anyway.

Unfortunately fitting this system requires the box to come out but minimal work is required to the box itself- basically a captive nut needs to be welded to the lid, a separate spring plunger installed for reverse (this is virtually flush with the lid and measures roughly half inch in diameter) and the selector rod needs to be freed from the selector forks. Assuming my understanding of the AV system is correct the interlock washer would need to be flipped over and a new small ramp cut out (an easy task- the ramp is only about 1/10th inch deep).

The system works on a test gearbox I have and provides a smoother selection of 5th, finding 4th or 3rd means merely pulling back out of 5th, the spring then naturally pushes the lever across the gate to the correct position for their selection.

Measuring the clearance on my own car there is ample room to fit and remove the device with the gearbox in the car- a bit fiddly but only as bad as removing/fitting the carbs and a lot qiuicker!

If anybody wants any info feel free to contact me- if there is sufficient interest I could get a few made. I'm not sure about the costs since the one I have was a one-off but I imagine making a couple would be cheaper than what it cost me.

My number is 0151 480 8400

Regards


John
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PostPost by: garyeanderson » Sat Oct 02, 2010 11:09 am

This was posted in the for sale section several years ago and it was as close to a do it yourself kit as I have seen on this forum. For the amount of talk that it recieves, this conversion for the "masses" has gone no where. I guess that it may be a "fun" project but then when it comes down to it it doesn't happen all that much in real life.

Gary

p.s. - maybe if these "plans" were posted it might be something that a bright spark could do?
****************************************************
Hello all

Back again with the same item. I advertised this some months ago but as you can see a sale didn't follow so here goes.

This is a Ford Type 9 item modified in a number of ways. To "filter out" the casual inquiries I've included as much info as possible in this listing. Should anybody want more details please e-mail me and I'll get back to you quickly.

Basically this is an old idea- the person who designed the conversion did so back in 1982 and has had the modified box in his own car since that date so it's well proven. He designed three conversions on this gearbox each of varying complexity but they all do the same thing so there is no "better" modification as such.

The first involves not surprisingly the simplest changes to the internals and this is the one in my own car (since 1999 in fact) and keeps most things as standard but relocates the lever forward. The final position of the lever is almost at the same point as the 4 speed item and uses a very short remote to further shift it forward and angle it backwards as per original. In the case of my car I never bothered but simply used the lever without any extensions. If any one wants to see how it looks as installed in my car I 'll e-mail; some shots.

The second design is more complex than above (this is the type I'm selling) and modifies 5th selector fork, relocates the selector locking mechanism for 5th and relocates the spring loading mechanism for 5th in a different position. More involved but still works the same way ie no difference in the change quality.

The final conversion involves much more precision engineering and modifies 5th selector for to bring the selector for 5th through into the main casing and eliminates the need for 5th to have its own lockout mechanism. From an engineering perspective this is the most elegant but as I said it doesn't work any differently to the others.

Some points to bear in mind-

This conversion is not suitable for spaceframe chassis cars because the tubes at the beginning of the centre spine are too closely set for the tail of the box so it will only fit original lotus chassis or the non-spaceframe early spyder units.

You need other items- an alloy bellhousing from a rally Escort- specifically a "BDA to Rocket box" unit. Ford very kindly retained the same fixing pattern so this bolts directly onto the Elan block without the need for a sandwich plate. It also has the starter mounts on the correct side and uses the same clutch slave cylinder mounting points. Cost of the bellhousing is about ?120 secondhand or about ?190 new from BurtonPower Ltd.

Since the splines on the rear of the Type 9 differ you need to have a new propshaft made by GKN who charge about ?130 inc balancing.

You also need a different clutch friction plate- about ?70 from Demontweeks (it's a MGB racing item I believe). Don't use the standard sierra item- it'll fit but might slip under hard loads.

A modified speedo cable is also needed to match the head of the instrument to the gearbox drive- cost is about ?20 or you can do it yourself for about a fiver.

A different gearbox support bracket is also needed- this is the last item to be made (you'll see why when you install the box). The original rubber mount is retained but the bracket is bolted to the 5 speed captive nuts thoughtfully supplied by Lotus so no mods here to the chassis.

I don't know about the Burton item but I'd strongly recommend that the holes for the starter have stainless recoils fitted since these bolts need to be very tight as we all know.

Finally- and a very important point- you need to fit the clutch and bolt the box to the block OFF THE CAR and rig up a temporary hydraulic system to the clutch. With the box in gear and with an assistant ensure that the clutch frees off properly. The reason for this is that the dimensions of the alloy bellhousing vary very slightly from the original. In some cases this alters the leverage/travel of the clutch fork and it might be neceassary to have a new post made by a precision engineer. Mine cost about ?15.

Fitting is a straight swap so if you are capable of removing an engine/transmission it's a diy proposition. Mine took a few days because I made the mistake of having the gearbox bracket made before the engine was installed and couldn't clear the centre pipe of the exhaust- but that was the only problem.

How does it work in practice? Depending on the tyres used and the diff ratio 5th should give around 22 mph/1000 revs. My car uses a 3.54 diff with tyres of 1836mm rolling circumference. This equates to 22.7 mph/1000 revs. Don't expect much noise reduction however- it will never be a quiet car. Change quality is excellent. Internal gearing is slightly different- some figures are below-

Std Elan-
1st (2.97) 5.784 mph/1000 revs
2nd (2.01) 8.546 "
3rd (1.39) 12.36 "
4th (1.00) 17.18 "

All above with 3.77 diff and tyres of 1737mm rolling circumference.

Figures for Lotus 5 speed are-

1st (3.2) 5.368
2nd (2.01) 8.546
3rd (1.37) 12.54
4th (1.00) 17.18
5th (0.80) 21.47

Sierra Type 9-

1st (2.97) 5.784
2nd (1.97) 8.72
3rd (1.37) 12.54
4th (1.00) 17.18
5th (0.82) 20.95

So why am I selling this box? The gearbox in my car has a bearing problem with 3rd (not related to the modifications) so I built this one to do a straight swap with mine to save time but since had a change of thought. I've now decided to retain my own box and try another modification involving maching excess metal of 5th driving gear to see if this alters in any way the feel of the gearchange. For those not familiar with this box 5th is outside of the main casing (unlike more contemporary designs) which means that 5th driving gear is continuously revolving. Reducing the amount of metal on this gear will reduce this flywheel effect and should lighten the feel. Since this is untested I'd rather do it on my own car.

One last point about the box for sale- it has an interesting history. Some years ago Ford were carrying out similar experiments and played around with a few boxes. The idea came to nothing so the boxes were discarded. I ended up buying a few! In effect they were new ie had never been fitted to a car so the internals on the one for sale have never seen any wear unlike the other conversions being offered which use boxes from scrapped cars.

If anyone is seriously interested I can (given reasonable distances) demonstrate how one works in my own car but due to my insurance I regret only I can be pilot! I'm in Liverpool but do attend some of the shows so I might be able to meet up.

Anyone wishing to talk boxes feel free to call me on 0151 480 8400- John. [email protected]



Finally- very last point I'm doing one very minor job on the box hence the term "shortly" at the beginning. Re-assembly is only a matter of about 30 minutes work but I'm still waiting for somebody to finish the item- about another week probably.
Attachments
t9elan3.jpg and
t9elan2.jpg and
t9elan1.jpg and
t9elan.jpg and
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PostPost by: Foxie » Sun Oct 03, 2010 12:01 pm

Hi John,

I have an AV T9 which I fitted 6 years ago.

I attach photos of the cam and plunger. The cam ramp is only ramped on the reverse side, the 5th gear acts as a stop.

The selector left right detent is fitted in the rear casing.

I'm really happy with the AV T9 except for one thing, that is the protrusion of the plunger tower in the top cover. As I have a TT large bore exhaust manifold, I find it much easier to remove/refit the engine and gearbox as a unit, with the manifold in place. The plunger tower catches on fibreglass at the front of the transmission tunnel, so I have to first remove the plunger to remove the engine gearbox assy, and re-fit it again while the engine assy is going back. The plunger was relieved on on side to match the ramp, but there was nothing to key it into the correct orientation when refitting on the blind. I rectified this by relieving the plunger conically.

I have been thinking how to rectify this problem, a leaf spring would give more clearance.

I'm interested in your solution, I'm not sure whether it would suit me.



worzel wrote:Hi

See my other post today- this one might specifically interest those with T9 boxes already in their cars.

I'll stand corrected on the last point but my understanding of the Alan Voights system (which also screws into the lid) is that a ramp/cam effect acts as limit on sideways lever travel in the neutral plane.
<snip>
To obtain reverse one pushes the lever hard over leftwards to overcome the spring loaded ramp which is effectively a cut out in the interlock disc in the main casing. Selection of 5th operates in a similar fashion ie you have to overcome a stepped resistance.
<snip>
If anybody wants any info feel free to contact me- if there is sufficient interest I could get a few made. I'm not sure about the costs since the one I have was a one-off but I imagine making a couple would be cheaper than what it cost me.

John
Attachments
Top cover & plunger.jpg and
Selector cam.jpg and
Selector detent.jpg and
68 Elan +2, 70 Elan +2s
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