M32 Generator gear form

[Hamwic]

Hi All,

Dismantling and inspection of the 500 OHV M32 has begun, and miraculously things are looking pretty good in the engine department so far. The drive gear that attaches to the BTH genny ("A" type with the eccentric adjustment and extended nose) has been robbed at some stage in the past, and luckily is not lurking in the bottom of the engine.

The drive gear has 25 teeth. Can anyone confirm the number of teeth on the missing gear, and its DP please?

If the picture in the manual is correct, it looks like it might be 21 teeth, but I have done the maths using the HPC page and it seems that the correct gear to mesh would again be 25 teeth at 18DP.

It would be good if someone could confirm this before I buy what might be another desk ornament from HPC.

Many thanks!

[Dave]

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[Aero]

In the absence of any other replies it might be of interest that the Aero 600 has a similar arrangement, and uses a 25 tooth drive gear on the crank, mating to a 21 tooth gear on the generator. I have a 21 tooth gear handy if you need any pics or measurements

[Hamwic]

Hi Aero,

Thankyou for the information re the number of teeth on the driven gear. I am pretty sure yours will be the correct size, as I now realise it should fit through the dynamo spigot hole in the outer case, which is 1 5/16" diameter.

I have today received the 25 tooth gear from HPC, and it is too big, so despite my best attempt at measurement of the shaft centres, 'taint right! I shall grovel to them tomorrow to see if I can exchange it for a 21 tooth, but some pictures and the dimensions from yours would be most welcome.

Cheers for now
Doug

[Aero]

Hi Doug,
here are the pics & dimensions of that 21t gear.
Its 32.2mm diameter across the teeth.
The teeth are 9.4mm long & 3mm deep.
The whole thing is 23.5mm long & the nut recess is 12.2mm deep.
Hope this helps.
Mark








[Attachments converted to linked images. 25Nov21 -Doug]

[Hamwic]

Hi Mark,

Thanks for the timely information - the dimensions all make sense and an HPC G18-21 gear should do the trick. Now for a bit of negotiation with HPC about my 25 tooth example!

Thanks once again
Doug