singer le mans gearbox

For now, I lumped all the pre-war cars together, I would LOVE for there to be enough demand to split it into groups (hint...hint, post here about your pre-war Singer)
Mall
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singer le mans gearbox

Post by Mall »

Hello

Being new to singers,my first aquisition, I have found this excellent forum and would appreciate advice regarding a recent gear change problem.
Moving the car around in the garage yesterday all was well with gear changes as normal.Then gear changes became eratic culminating in the gear box being stuck in a forward gear.I cant find neutral or reverse, all gears seem to move forward .The gear stick appears to be normal moving through the relevant gears but not finding neutral or reverse. My first thoughts are that it could be a breakage between the selectors and the gear box. Any advice would be much appreciated.

Thank you in anticipation

Mall
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Peter McKercher
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Re: singer le mans gearbox

Post by Peter McKercher »

It's likely that it is second gear that you are stuck in. If this is the case, you are probably missing the locking pin which should be located between the two ball bearings that you will find in semi circular grooves in the selector rails. It's a 3/16 diameter pin that fits in a drilling between the two bearings.

While this condition might not occur under normal driving conditions, it will lock up tight if you don't come to a full stop before shifting into reverse. If you were shunting the car around, you probably didn't come to a full stop.
Peter McKercher
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Pre war Singer Specialist and Collector
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Mall
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Re: singer le mans gearbox

Post by Mall »

Thank you Peter for your reply

Having taken off the gear box lid I cant find the ball bearings referred to or a locking pin. Should the ball bearings and locking pin be visible on removal of the lid or is further dismantling required

Regards

Mall
DarcyG
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Re: singer le mans gearbox

Post by DarcyG »

Hi having just put my gear box together for the first time ( after years of being left apart by one of the previous owners) I am not sure what part you are referring to Peter. I had three ball bearings, one for each selector that are accessed from the top. Plus each shaft has a screw locking pin that should be wired to prevent it coming loose.

Attached is the drawing I have (ignore the comments), I can't see the locking pin?
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Re: singer le mans gearbox

Post by DarcyG »

Drawing
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Peter McKercher
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Re: singer le mans gearbox

Post by Peter McKercher »

Here is a piece that was written years ago by Ian Blackburn on the issue.

This is actually a common problem with the Nine Sports and Le Mans gearboxes with remote control gearshift.

It may be noted that if any attempt was made to engage reverse gear, unless all forward motion had ceased and a few seconds pause were allowed, that second gear would engage and the selectors were incapable of either selecting any other gear or releasing second.

To understand this problem, one must realise that when reversing, FIRST GEAR is locked in its neutral position and the reverse pinion is brought into mesh with both parts of the first gear pair. If the locking mechanism is not operative, it is found that as reverse is engaged, the first gear pinion, together with its selector rail and fork, are dragged forward on to the second gear position. While some resistance is provided by the detent ball and spring at the front end of the selector rail, it is not sufficient for hurried or crashed changes. Consequently, positive locking is provided near the rear end of the selector rails.


gearbox.jpg
gearbox.jpg (77.08 KiB) Viewed 2580 times




The mechanism consists of two ball bearings locking into semi-circular grooves in the selector rails The centre rail has two such grooves, opposite each other, and is drilled through. A 3/16” diameter pin operates in the drilling. All this operates within a drilling through the aluminium of the gearbox top casting, located horizontally near the rear end, and closed with a threaded plug (See iIlustration).



It will be seen that when the lst and 2nd rail is moved from the neutral position, it displaces the ball bearing to lock in the groove in the 3rd/4th rail, which in turn acts on the pin to lock the ball bearing into the reverse rail. Similarly, selecting reverse locks both other rails. When 3rd or 4th is selected, both balls are displaced and both other rails likewise are locked.



Now the condition previously described is often caused because the pin above is missing (having been lost when some other job was being performed on the gearbox top). This same mechanism prevents two gears being engaged at once. It could prevent a very expensive breakage — make sure yours is working
Peter McKercher
Vice President - NASOC
Pre war Singer Specialist and Collector
Automotive Historian
Author of "Racing Roadsters"

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DarcyG
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Re: singer le mans gearbox

Post by DarcyG »

Thanks, did not have, didn't know and therefore did not put any in, so out comes my gearbox, again. You can clearly see now that I know, where these two balls sit.
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DarcyG
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Re: singer le mans gearbox

Post by DarcyG »

Peter do you know the size of the balls? Or are they just what fits? Plus while the pin is 3/16, how long is it? Is it just the length of the space in the selector shaft?
Last edited by DarcyG on Thu Oct 08, 2015 8:34 pm, edited 1 time in total.
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Peter McKercher
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Re: singer le mans gearbox

Post by Peter McKercher »

It actually requires the balls plus springs for tension. I'll get some measurements and pictures.
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Automotive Historian
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Mall
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Re: singer le mans gearbox

Post by Mall »

How critical are the three threaded plugs that fit in the rear end of the gear box selector housing.Mine are missing.

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Re: singer le mans gearbox

Post by Peter McKercher »

If you mean on top of the housing, quite critical as they house the springs and ball bearings. I'm assuming you are missing these as well. I will get photos and measurements for you and Darcy when I have a few spare moments. Unfortunately it's our Thanks Giving weekend and things are quite busy.
Peter McKercher
Vice President - NASOC
Pre war Singer Specialist and Collector
Automotive Historian
Author of "Racing Roadsters"

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DarcyG
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Re: singer le mans gearbox

Post by DarcyG »

Hi, and have a a great Thanks Giving. We have the Bathurst 1000 V8 Super cars this weekend. see http://www.v8supercars.com.au/events/ne ... hurst-1000

The following is from a member down here:

"The three detent balls (under the springs) are 3/8”.
You might have to experiment with the springs. Too hard, difficult to get out of gear. Better to be too soft if anything. Don’t rely on those springs to hold things in gear. They are only there to give a “feel” when going into or out of gear.
The two interlock balls are 7/16”
The sliding pin is 1/4” dia. and the one I found was .407” long.... 13/32”. A strange size. It appeared a bit worn on the ends so may have been 7/16” when new.
You could start with 7/16” and check that everything works/fits then grind down as necessary. It is a hardened pin like a dowel pin!"


Note the 3/16 versus the 1/4 above. Where some cars different? Very possible. From my discussions the ball size and relative length of the pin are critical - they must work together.

Peter you might confirm this detail with yours when you get a chance. I will wait for your feedback before I take the top off my gear box again. I am hoping I can replace it without taking the full box out.

The screw heads and the caps on the other end also keep the dirt out!

Mall, thanks for raising this item before I ventured further.
Mall
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Re: singer le mans gearbox

Post by Mall »

Hi

The three plugs I referred to and am missing should be screwed into the rear end of the selector housing sealing the rails. When removed they allow the selector rails
to be removed following removal of the forks.When dismantling I found that heavy springs were fitted,to mine,the pin was in place but the two ballbearings were missing.

Mall
DarcyG
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Re: singer le mans gearbox

Post by DarcyG »

What the dimensions of the pin?
Mall
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Re: singer le mans gearbox

Post by Mall »

Sorry,I did not measure the pin and its now reassembled.

Mall
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