BCA milling machine/ pulley drive system

Dear all,

I'm making a comparison of the best drive system from Hauser Mill to Deckel pentograph GK2 and now BCA milling machine. Does anyone owns a BCA mill and able to share some light over the pulley drive system as well as the constant belt tension it can offer when the spindle head moves?

Thanks ahead.

Regards,

Steve Wan

Hello Steve

Me again! I think the following pictures should explain better than words:

Any questions, please ask, I have/will update the pantograph drive pictures thread aswell.

William

I have one of these (that a bit of Dorset Echo in one photo..? .) and I must admit that the rear pair of pulleys confuses me, though I notice you have the belt passing under them in one or two cases. On my machine the belt usually runs clear of them, but in any case they never seem aligned at the belt angles.

Mine came with a rather dubious inverter to power its original motor so I replaced both with a new motor and controller (Newton Tesla) but I was careful to fit the original pulley, and in its original location including height. I had to make an adaptor plate for the task.

Nevertheless, whether those jockey pulleys do any jockeying seems to depend on their mood at the time, and I am not sure if that is natural.

I am not convinced either, that the tensioning spring does much, but I have noticed that even when the tensioner is out at its maximum, the belt rubs slightly on the body of the machine if used on the lowest speed spindle pulley.

I suppose it's possible the belt on my BCA has stretched with age. I've not tried asking Tenga if replacements are available but if their collet prices are a guide, they won't be cheap!

You can buy a good quality Polyurethane belt from the guy on the "Lathes" website.

I have one on mine and it is very good.

Phil

Hello

The rear jockey wheels that I have run the belt over and under in some pictures are only to be used when the head is tilted, not when vertical. As I demonstrated they are there to keep the belt square off the motor pulley.

The newspaper is a Waitrose own brand thing, it’s the only plentyfull supply of free good fire lighting paper(and bench protector)!!

Even with the original motor the belt does stilll rub on the headstock casting on the slowest pulley combo, however on my previous machine which had a longer belt and a smaller diameter it didn’t.

The spring does seem to work on my machine, better than my previous machine, it has to be the right length too long and when the belt is released it launched the pulleys across the room! The spring in the machine above is perfect as the belt can be totally removed and the assembly remains. I do still have belt slip when using a slitting saw not that that is an issue, saves the saw blades!

Yes Tenga are not cheap, but nor where the machines back in the day, mine in 1977 with all the tooling I have would of been around £14000 in today’s money!

William

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The original belts were cotton [maybe reinforced with a synthetic strand ... I'm not sure] twisted from ‘ribbons’

I replaced mine with the textured green polyurethane version supplied by Tenga [possibly 20 years ago] at a cost of about £40

... It’s very nicely made, and allegedly Swiss, but apparently-similar belting material [for DIY butt-welding] is available cheaply from China these days.

MichaelG.

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Edit: __ There’s even a U.K. supplier on ebay offering it 

https://www.ebay.co.uk/itm/2-10mm-Dia-Round-PU-Conveyor-green-Belt-Polyurethane-Belt-for-Drive-Transmission/284145449903

Edited By Michael Gilligan on 20/03/2021 18:14:35

Thank you for the advice gentlemen.

I'd not realised the rear jockey pulleys are only for when the head is tilted.

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The belt on my BCA appears to be a mixture of cotton and rubber.

I've a Taylor-Taylor-Hobson (so it is old!) engraver too, also awaiting a new drive belt, and it would make sense to combine the order, but first see if the machines will even use the same diameter material.

I've also a part-built Stent T&C grinder for which the same round belting may be suitable (with appropriate pulleys - the drawings assume a V-belt).

Hi William

Wow! Thanks a million!

I see, the back pulleys are used to get the belt in-line for headstock tilts milling operations.

All the BCA photos will be printed and recorded in my library. A wealth info for my mill design

Please see my 3rd photo in the album, my mill stand is ready. I look forward to your Pentograph photos in the near future. Once again, thank you from the bottom of my heart!

Regards,

Steve Wan