Belt drive question

With only 3" between shaft centres, I think you will be struggling to get any belt typeto work as your pulleys would need to be quite small. At 10K rpm aswell, you might have additional issues. I would have thought gears would have been a better solution here. Mike

I think that the only easy way to go would be with toothed 'timing' belts, but gears would be a more professional method, but require more engineering to get the centres and meshing correct. I assume you will be working with small cutters as3300 rpm is quite fast. If you wish to get things going slower, a layshaft could be used to give a further

According to Gates DFpro, it's doable with toothed belts/pulleys.

Link below shows the possible combinations.

If the shaft centres are 3" apart and the radii of the two pulleys are r1 and r2 then you need r1 + r2 = 3 (give or take a bit for clearance)

If you want a speed reduction of 3 then the circumference of one pulley has to be 3 times the other so r1 = 3 x r2

So we have 3r2 + r2 = 3 or 4r2 = 3 or r2 = 3/4"

and r1 = 3 - r2 = 2 1/4.

So a 1.5" diameter pulley driving a 4.5" diameter gives you your speed ratio and a 3" separation of centres.

Sounds perfectly do-able with poly-V drive, though you'll have to settle for slightly smaller pulleys to allow for a bit of clearance? You also need some movemenrt somewhere to allow setting up of belt tension if you go that route.

I used a poly-V belt to drive a countershaft from the motor on my lathe, I manufactured both driver and driven pulley using the JohnS "tap in the tool post" method to cut the grooves. The difference in the thread angle and the belt "v" angle has proven to be a non issue in real life use.

The other nice thing here is you can choose any odd ball diameters of pulley to suit your need and they are easy to make.

Steve

Steve wrote: [...]

I'd ask about that, but it seems obvious enough. Only problem, where can I get a 0,092"/ 2.34 mm pitch tap? What tap did you use?

The difference in

Good to know.

I rather fancy a belt drive which will slip if something goes >clonk!

Thanks.

I may go with a poly-vee belt instead, but that's useful to know.

-- Peter Fairbrother

Use an 11 tpi Whitworth form pipe tap of Coventry die insert.

I used a single point tool ground to 40 degrees included angle and

I've done them with a single point tool (DRO makes it much easier) and finished with an 11 tpi hand chaser. The pitch difference taken off by the chaser is minimal.

Tim

I've done them with a single point tool too as my machine wouldn't be solid enough to use a 11 tpi tap. I use a HSS tool ground to 40 degrees with the tip ground down to 0.022" width and use it to cut each groove to a depth of

Mike

"Peter Fairbrother" schreef in bericht news:48a2742c$0$26074$ snipped-for-privacy@news.zen.co.uk...

Could a link belt, e.g. powertwist, be useful? Can be made in any lange,

Thanks for thew suggestion (and thanks to everyone else too!), but I think a poly-V belt is the best way to go. Good grip, good strength, very flexible, low mass and therefore high speed, plus it will slip if there is a crunch.

The pulleys are not hard to make - by the way, I found a scavenged washing machine motor with a hardened J size pulley, it's the wrong diameter but I think I can use it to make a tool to clean up the rib profile.

That leaves finding a source for the belt, which isn't going well - any ideas?

Thanks to all again,

-- Peter Fairbrother

Peter

Try Tony at lathes.co.uk, he advertises Poly V belts.

He did a bespoke round belt for my Naerok pillar drill recently - very efficiently and at a good price.

Cheers

Peter

DFpro didn't find any workable solutions using their range of v-belts/pulleys. It did come up with 2 'problem' drives, but I never actually looked to see why they didn't work.

moray

Too difficult - honest - cut it once as above really easy and works well

That'll depend, to some extent on the possession of a 5/8"BSW tap or die box insert.

Mark Rand RTFM

BSL-Brammer

But I suspect your requirement will to prove to be for a shorter belt than is readily available.

I buy here, quick and a huge choice