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George Eagle
United Kingdom
3245 Posts |
 Posted - 25/08/2011 : 20:05:22
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I have just received a copy of the book by Peter "Banjo" Meyer who has written a much acclaimed book on the pre-select gearbox. The book is very detailed, has a large number of illustrations and comes with a video animation on a DVD. The preview I read stated that anyone with a modicum of skill and the right tools could strip and rebuild a pre-selector gearbox.
Details can be found on www.preselectorgearbox.de - I bought mine via the Riley Register. I think this is a must for anybody who has such a gearbox fitted to their car!
I have no connection with the Author.
George Eagle |
Edited by - George Eagle on 25/08/2011 20:07:50 |
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David Allison
United Kingdom
665 Posts |
Posted - 26/08/2011 : 10:06:40
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George - the posted link is a dead end I am afraid.
The info via the Riley register though is very good - although mostly concentrates on the Armstrong box rather than the ENV.
The internal workings of the ENV are smaller and more fiddly but the basic construction is very similar - the important thing with pre-selectors is that you work methodically and stick to a number of basic rules of thumb.
The Armstrong box is a larger unit to a later design with improved and enlarged drums and gears to cope with more horsepower.
The standard Armstrong box has bronze bearings inside the gear drums and the main "tweek" is to convert these (as far as possible) to run on roller bearings throughout.
The Riley version has (in my opinion) too wide a spread of gear ratios for an MG and it is well worth using the "close ratio" gear sets made for the Riley Sprite instead of the standard touring ratios.
MG boxes were all made by ENV and also supplied with different ratios.
The standard MG gear set (called the close ratio set by Riley people) for the ENV 75 box was fitted to K saloons and tourers - the close ratio set was fitted to the sports and racing cars.
The "R Type Box" was a yet closer gear ratio with a very high bottom gear and was fitted to a number of other racing cars at the time too (including the Eccles Rapier).
Utilising the deeper sump to hold more oil and keep everything cooler - these boxes were the ultimate development of the ENV 75.
My dad had one of these boxes in NA 0307 for a time in the seventies to nineties when he was racing the car regularly - but in truth the great driving ratios put huge strain on the final drive when making fast starts (often resulting in busted diffs and 1/2 shafts) - the gearbox was exchanged when we built the NO special for a close ratio Armstrong box with the R type box returning to its original R type chassis.
The ENV 75 is designed for engines of upto 80 HP (hence the type number) and struggles with highly tuned racing engines unless cared for and kept cossetted.
The larger ENV 110 is rarer than an Armstrong and therefore it is the de-riguer upgrade when tuning a MMM or indeed most other pre-war racing cars.
The amount of information on these boxes is quite good and there are a number of reputable rebuilders - however there are very few black arts involved and the rebuild of the pre-selector is actually quite easy.
Regards David |
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Dow
United Kingdom
490 Posts |
Posted - 26/08/2011 : 11:39:21
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Hi David.
My N has the large Armstrong in it. Can you give me a page link to the info you refer to ?
I have an owners Service manual for a Saphire which has several exploded diagrams of what seems to be the larger Armstrong Box.
Regards
David D |
Edited by - Dow on 26/08/2011 12:07:55 |
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Nick Feakes
USA
3414 Posts |
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Otto
Germany
63 Posts |
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