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4 speed box on a 1929 coil engine...

Do any Forum members have experience of fitting a four speed box to an early coil (1929) engine please?

If so, what modifications would you recommend to the clutch mechanism and/or anything else, if any?

Many thanks,

R

Re: 4 speed box on a 1929 coil engine...

Yes Ruairidh. I swapped the 3 speed release bearing and levers for the 4 speed release bearing and levers and it worked fine. However, you might need to do some adjustment of the lever stops to get the clearance right. I did that with the engine and gearbox on the bench using trial and error. Much better than finding out it doesn't, quite, work once it's all in the car.

However, I didn't like the conversion at all. Four speed might have an extra ratio and be more flexible but the three speed's much more 'fun'- at least it is if your three speed is c/r.

Steve

Location: North Yorkshire

Re: 4 speed box on a 1929 coil engine...

My special has a four speed gearbox on a 29/30 vertical oil tube crankcase. No problems fitting using four speed thrust race and levers. Do use a Ruby type pedal lever with detatchable pedal pad though.

Location: back at home

Re: 4 speed box on a 1929 coil engine...

"Alice" has a four speed box, which I managed to fit without re-drilling the mounting holes. I was told at the time that I had to re-drill the chassis, but I didn't, for that engine.

It is a long time ago now (1976) but I think I:

turned the speedo drive housing upside down so the drive went straight up
to the PA speedo

re-fitted said drive using at least one countersunk setscrew to give me
an extra 3/8" clearance at the rear

probably used 5/16" engine mounting bolts for the same reason.

It was a tight fit, and the rubber coupling always rubbed the handbrake a bit, but I did manage it. I failed with another engine, later. Don't know why, by that time I wasn't so picky, so out came the drill.

I think I kept the original clutch release bearing, though it may have been modified.

Cheers

Simon

Location: On a hill in Wiltshire

Re: 4 speed box on a 1929 coil engine...

R,
I used the 4 speed thrust race and 4 speed toggle levers with modified mousetrap springs involving drilling the holes for them in the clutch cover plate. Can't remember how I drilled them sorry.
Dave.

Location: Sheffield

Re: 4 speed box on a 1929 coil engine...

Don't you have to move the engine forward to allow the gearbox to clear the front crossmember?
The speedo will be about 100% out unless you change the worm and gear too.

Re: 4 speed box on a 1929 coil engine...

Page 257 of "The A7 Companion has an article by FL Townend (1950)& a later (1953)comment by the editor suggested it was better to shorten the propshaft rather than move the engine forward
My 1932 AG tourer has a slightly earlier engine (about 10.000 numbers)& has been converted to 4 speed by moving the engine forward ...very close to the radiator. I think it must have a short pulley. The original 3 speed is with the car. It has a second speedo (not connected!)I have no idea what the clutch is like...I am a little way from getting it mobile.
David H

Re: 4 speed box on a 1929 coil engine...

Have had this setup on my '31 tourer for a long time. The chassis has not been re-drilled. It has a 3 speed cover plate combined with the 4 speed pressure plate, release bearing and toggles.

If you drill the 3 speed cover for mousetrap springs using the a 4 speed cover as a drilling jig, you'll find that the coil portions of the springs will be hanging in mid air as the three speed cover doesn't have the radiused seating groove of the 4 speed version.

It's correct for the year of motor you're doing anyway, but you have to use the bacon slicer starter to get sufficient clearance over the taller 4 speed box, rather than the later rear facing starter.

Location: N W Kent

Re: 4 speed box on a 1929 coil engine...

Hi R,
I have done this on my November 28 top hat R saloon. It is possible to leave the engine in the original position if you use countersunk screws in the layshaft retaining bolt holes instead of the hex head bolts this gives about 3/8 " more room. If you are using a short chassis with uncoupled brakes the main problem is the front brake cable will rub on the gearbox housing in the area of the reverse idler / Oil filler bulge. This can cause the car to pull to the left. I still need to form a" cunning plan " to minumise this (roller- pulleys to re route around ?) This said I have driven the car many miles since.
Clutch-wise I modified the pressure plate to mousetrap springs by grafting -turning and welding the later toggle plate to suit along with the hammerhead levers - All this works well.
I have used a Bacon slicer starter. on 12 volts and a 4 speed herringbone crash-box which gives a great hill climbing ratio with relative silence. First gear is lower than any other box and great for hill starts with a caravan / off-roading etc. Nice engineering in these too and indestructable.

Cheers Steve

Location: Wellington NZ

Re: 4 speed box on a 1929 coil engine...

I forgot about the cable rubbing on the 'box. It had been doing that before I got the car, and had worn some very deep grooves in the casing.

I ran it through a short length of Bowden outer - old speedo cable outer, maybe - held on to I can't remember what, with a couple of turns of copper wire.

Simples.

Simon

Location: On a hill in Wiltshire

Re: 4 speed box on a 1929 coil engine...

Ruairidh, I recommend that you contact Andrew Jarmin or Malcolm Watts of the Cornwall A7Club. They have done this conversion to more than a few three speed A7s due to the 'Cornish Alps' hindering upward progress. Everyone who has had the conversion done locally (including me) would not go back even though missing clutchless gear changes and melodic sounds coming from the gearbox. Far better than the sounds from the driver stuck on a one in 'very little' local hill, and that's if somewhere can be found to turn and go up in reverse.
All the best,
Peter
Sunny Cornwall

Re: 4 speed box on a 1929 coil engine...

I seem to recall the floor support bracket on the passenger side has to have the rivets ground off, reversed and bolted back on. The floor has to be cutaway to accommodate the oil filler plug area. The splined tail shaft drive flange can be exchanged for one from a 4sp crash box if you are still using a fabric universal. I'm guessing you already know all this so I include it for others. cheers Russell

Location: oz

Re: 4 speed box on a 1929 coil engine...

I made sure the 4 speed filler plug was tight and left the floor as was, checking the oil level and filling via the gear lever hole like the 3 speed.

Re: 4 speed box on a 1929 coil engine...

For the 4 speed box I cut off the boss holding the gearlever and rewelded it back on the gearbox top further towards the driver's side and cranked the internal bit of the gearlever. Filed down the gearbox top enough to allow the 1930 to 1932 rearward facing starter motor and housing to fit on. This was 25 years ago and so I forget the finer detail. It still works ok. I did this to make it look slightly more authentic for my ulster replica and also because the bacon slicer starter creation should have been left at the meat factory where it belongs.
Dave.

Location: Sheffield

Re: 4 speed box on a 1929 coil engine...

Thank you everybody - here and off-line - who contacted me. I am very grateful for all your experience and advice, it is very helpful.

Re: 4 speed box on a 1929 coil engine...

Just one more mod you will probably want to do. Change the brass spiral drive from a 3 speed box to the 4 speed box--it is held in drive by the drive flange , or the 3 arm flex drive boss on the early 4 speed. I think there is a slight mod to do to the brass spiral (I did this many years ago). you will then have the correct ratio for the PA speedo.

Re: 4 speed box on a 1929 coil engine...

Thank you Ken.

Re: 4 speed box on a 1929 coil engine...

Not sure of the value of mousetrap springs. I use a 3 speed box with 1925 engine & have a 4 speed release bearing and the later clutch fingers. No mousetraps, no problem.

Re: 4 speed box on a 1929 coil engine...

Ruairidh

I have thi 4 speed arrangement on 1932 car detail on the DA7C website. Which should apply to a 1929 A7.

http://www.da7c.co.uk/technical_torque_articles/3_to_4speed_gearbox_conversion.htm

Douglas

Re: 4 speed box on a 1929 coil engine...

Thank you Douglas and Charles.