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doctorbob
United Kingdom
145 Posts |
 Posted - 11/03/2008 : 09:01:08
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What would be the most appropriate clutch setup if one was to connect a supercharged J2 engine to an ENV75 preselector gearbox?
Would it be the J2 clutch with heavier springs?
Cheers Bob |
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kimber
United Kingdom
1529 Posts |
Posted - 11/03/2008 : 09:39:02
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I used an ENV 75 on my (blown) P-type for about 10 years trouble-free. The car was fitted with no clutch. It was perfectly manageable both on the road or track. The idea is that the first gear band works as (instead of) a clutch.
I made an adaptor plate to fit the flywheel to which was bolted a spider and flexible drive coupling from a 2-litre Lagonda, the splined bore of which was a perfect fit on the ENV input shaft. It also got round the problem of the very short input shaft on the ex-Riley box I was using as I simply made the adaptor/spacer to the required thickness to 'fill the gap'. |
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Gerhard Maier
Germany
873 Posts |
Posted - 11/03/2008 : 12:22:13
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Bob,
I have no direct experience in fitiing a ENV75 to a J-type, but did it on other MMM-cars. As "kimber" say's, you use only the flywheel and no clutch. There are various methods to connect the input shaft of the wilson box to the flywheel, and it mostly depends on the length of that input shaft. Often propshaft-forks and flexible disks from a M-type are used, or sometimes also a adapter-plate bolted to the flywheel.
If you want a photo or more info, send me a mail.
Gerhard |
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doctorbob
United Kingdom
145 Posts |
Posted - 12/03/2008 : 09:52:52
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| Thank you for the informative replies gentlemen. Gerhard I've dropped you an email. Bob |
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Richard Hardy
United Kingdom
2159 Posts |
Posted - 12/03/2008 : 14:46:40
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You may wish to consider the shear weight of the ENV75 which on a J type just hangs to the bolts in the back of the block, ie no crosstube. A heavy non crosstube gearbox makes the J type arrangement prone to an oil leak in the rear main gallery between block and flywheel housing. The F type had a manual gearbox non crosstube box but got around the problem by having a different oil delivery system to the rear main.
There are a few points to consider to limit the risk of an oil leak.
1. Enlarge the block/ flywheel housing bolts to 3/8 BSF.
2. Modify the union between the block and flywheel housing so you are not just relying on the casting contact faces to make the seal.
3. Consider fitting block / flywheel housing torsion brackets to help prevent the twisting motion in the flywheel housing created by the weight of the gearbox
Finally, the ENV75 saps more engine power than a manual gearbox!
Regards
Rich H |
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David Allison
United Kingdom
665 Posts |
Posted - 14/03/2008 : 10:38:19
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The only J type factory fitted with a pre-selector was I think (I could be wrong) the Hamilton J$.
J4's are fitted with a cross tube mounting for the gearbox.
When Colin Tieche rebuilt the car though they did not have the pre-selector but had a ENV manual box and that was how the car was built.
I think that a pre-selector probably saps too much power and adds too much weight to a Midget (P or J)but this is a personal thing.
That said a pre-selector is a great toy if you have one - which of course my NA does.
The clutches were fitted to the road cars to save the transmission.
The high bottom gear on the pre-selector designed to suit the MG can cause problems to the final drive.
Dad went clutchless on the NA for a while to save weight - but broke so many diffs in racing starts that we re-fitted the clutch when we got the car back on the road in the early 90's.
The NO has never had a clutch but does have a flywheel and a starter ring - the racing cars often went without a flywheel too.
The clutch also saves the bottom gear band as well - the torque multiplication in first and reverse gears is very high and the clutch helps reduce the heat build up in the lower rations.
The NA has a twin plate clutch - it is the original and has never been re-lined as long as I can remember (although my direct involvement with the car is only about 30 years) - Dad might have done it when he first got the car.
The set up is similar to an L type flywheel, there is just no release bearing or connection to the pedal.
Rileys and Rapiers use a traffic clutch - this does have a release bearing and leaves the car with a "soft start" on initial pull away.
Again though the racing versions of both Riley and Rapiers were clutchless to save weight.
Andrew and Gerhard both explain ways of connecting the engine to the gearbox - both were used on the racing cars rather than road cars.
That said as long as you are carefull and dont try too many racing starts you should be ok.
I have to say though a better "non standard" modification to a J is to fit the ENV crash box - as fitted to the J4 and C types - even the F type box has better ratios than the J2 and PA box and the gear shift is a peach.
Having said that - there is nothing wrong with a standard J box really - dont carried away by the pre-selector being a cure all!
Also the ENV crash boxes are rare.
Pre-selectors run very hot and take up lots of cabin space (not something a J is famous for in standard form) on a hot day the heat build up inside the car is terrific and bordering on the unpleasant.
My advice is to leave your car with its standard box - the pre-selector has no real advantages and plenty of disadvantages.
Regards David |
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