Timing belts produce noise (and heat) as the speed increases - this is a fact!

I agree with you on this point, although it also applies to belts of all types.

Since we cannot agree on v-belt vs timing belt, perhaps we should compromise on a grooved belt . . . a.k.a.  'serpentine' as it is commonly called in automotive applications.

This would avoid the single disadvantage of timing belts . . they cost several times more than v-belts.

In this way, I can be satisfied with it's 'flatness' and you can find joy in it's  . .  'V' ness. 

Seriously, a groove belt is an alternative worth considering because it fall in price between the 'timing' belt and the 'V'-belt and the pulleys are stupid easy to make and since the grooves are shallow, the pulley can be small in dia . . . . so long as it stays within the flex radius spec so we can be scientific. 

I agree on the Poly V-belt (or a grooved belt like you say) Already mentioned it being used on industrial lathes. Not sure about the pricing though - was getting mine for ridiculously low prices - something like $5 for a 17" XL belt. Much cheaper than the polyurethane reinforced V-belts I've been buying - about $20 for about the same size belt. But then it may be just my supplier

Daniel

Seems we are on the same page, albeit in different scales and with some symantics. I recall you are in the middle east and I am in the USofA.

Big multiple V-belts as one would find on a machine tool are called 'banded' or 'ganged' in my world. Also big V-belts can be had in 'matched sets' (matched for exact length, but separate belts.)

The little brother is called 'grooved' or 'ribbed' and in automotive speak is a 'serpentine' belt, although that desribes the arrangment and not the belt structure. A difference, (other than the obvious  . . . size) is that the grooved belt has traction material on the smooth side which is intended as a drive surface in a serpentine arrangement.

I'm not clear on which belt type 'poly v' refers to, but it seems that you used the term for both a big machine tool and Hood's little engraving spindle, so it seems the term is somewhat universal. And yes, your are right about suppliers also. A 'grooved' belt purchased from an industrial supply house might be $10. But the identical 'Serpentine' belt from an automotive store is $38.      Go figure.

"Wee Gearbox"... hmm... sounds good, but what is it anyway

Daniel

Well I will assume you know what a gearbox is so it must be the "wee" bit you don't understand
Wee is small 
Hood

Thanks Hood

Daniel

Did a bit of testing today with the coolant running through. Alu was cold after half an hour at 3000 rpm input. Output shaft was a bit warmer but nothing like it was before, I could quite comfortably hold the back of my hand against it

Hood

Good results

Daniel

Well its actually not
Decided to let it run while I was welding up a stainless anchor, after about half an hour I heard the sound change, went over to the mill and the output was not turning very fast. Felt for heat and it was ok on Alu and shaft like yesterday so removed from spindle and hauled it apart. Belt was all stretched and misshapen like it has had too much heat.
 Going to think about things and decide the next move.

Hood

Oh... sorry for that. It's strange. Must be something wrong with that particular belt you used or the pulleys. May be they were not meshing correctly... may be didn't have same tooth profile. Otherwise, I think, the speed was not that high to cause what you described. Could be a bad alignment of the pulleys...?

Daniel

Ha ha no sorry thoughts needed. Its been put down to experience Its how we learn, if you dont make mistakes or fook ups you are doing something wrong, secret is to move on and learn from the mistakes

Belt and pulleys I think are matched but as I never bought I cant be sure, they do look ok though. Pulleys were running true and tension seemed fine.
Gears sound like they may be my next move as it will hopefully allow me to keep things more in line with the spindle.

Hood