5 speed toothed belt drives

Hi

I wonder if anyone has made a 5 speed toothed belt drive similar to the round belt drive pulleys on the Dore Westbury mill?

I have a speed reducer on mine (not the oil bath original) and find that the round belt gives a poor drive on the lower speeds when a reasonable cut is used.

Any suggestions would be appreciated.

Regards

Ian

I would suggest that for the drive on a Milling Machine(or a lathe), a Poly V belt would be my choice, It would proberbly only require a 3 grove belt, maybe 4, there has been a thread on this subject in the last week or so. Ian S C

Hi,

Just another consideration, toothed belts are intended to give a positive drive whereas smooth belts - flat, vee, A or round are intended to slip under extreme load or jams to give a margin of protection to vulnerable machine parts or motors etc. Worth taking into account when modifying anything to do with drives.

Best regards

Terry

Which takes less power, a poly-vee belt or a traditional belt?

Reason for asking, my Centec 2B is under-powered, and will not run at high speeds until warmed up, and, the vertical head pulley seems to have damaged its key (or key damaged pulley) because one can turn it about 40 degrees on the shaft.

I'm thinking that I'll have to re-make the pulleys (unless by some luck, they are available off the shelf), and was thinking about a Poly-Vee belt if it might be better than the straight V one.

Another JohnS

I use the round plastic melt-the-ends-together belt from Chronos, and it seems to work well. But my DW is a three pulley Mk 1, so a 5/16" belt will fit; I think the Mk 2 pulley grooves are narrower, and a thinner version of the belt might not do so well.

I assume your speed reducer comprises gearing between the motor and the driving pulley, putting the belt at the low speed with high torque end of the drive train. It would be better to have the gears between the driven pulley and the spindle, subjecting the belt to high speed but .less torque, making it less likely to slip. But that might be difficult to achieve, given the layout of the DW spindle head .

Having fitted an ex-running machine DC motor and PWM controller, I don't seem to change from the middle pulleys very often. A 2HP motor is OTT, but even at low spindle speed I rarely have to find the ear muffs and unleash my epicyclic gearbox..

Andy

Edited By Andyf on 20/10/2012 16:28:25

Ian.

Here is a Dore Westbury Head I modified to polyvee belts a while ago works great,

http://groups.yahoo.com/group/tom_senior/message/340

Regards

Alan

I's be interested to details, Alan, but the Tom Senior group is restricted to members only. Are you able to link to your conversion anywhere else?

Andy

John,

PolyVee is much more efficient than any traditional vee belt.

... please check the recent thread, where I posted the link to specifications.

Go for it ... I don't think you will regret it.

MichaelG.

[added hyperlink]

Edited By Michael Gilligan on 20/10/2012 18:25:12

Andyf

This is what I wrote in the Tom Senior group about pulley sizes. In use I have never changed the belt from the mid range

This is what I have made. I chose a max pulley size of 5" just for
material size. The sizes and ratios are listed below. I have
carefully selected these sizes to keep the same belt length in order
to avoid excessive adjustment when changing the belt to the other
pulleys. I also selected the mid range to cover most of my
requirements without the need to change the belt and use only the
inverter to change speed. In fact the higher and lower ratios are
only to cover the extemes which crop up occasionally. The centre
distance for my arrangement is nominally 254mm which gave a belt
length of 762mm (look up Arntz Optibelt group for belt lengths)

Pulley Diameters and proposed speed range for 1400rpm 1/2hp motor:-

Motor pulley 113mm dia, 72mm dia, and 30 dia.
Spindle 125mm dia, 89mm dia, and 45mm dia.

Speed ranges
1400 rpm x30/125 = 336rpm x 25% = 84rpm, 336rpm x 150% = 504rpm
1400 rpm x72/89 = 1133rpm x 25% = 283rpm, 1133rpm x 150% = 1700rpm
1400 rpm x113/45 = 3516rpm x 25% = 878rpm, 3516rpm x 150% = 5273rpm

I believe that an inverter may adjust over a greater speed range but
this seems an ok nominal.
Hope this is some help I will put some pics in my photos for you.
Regards
Alan

Alan,

Very useful information and photos !!

Thanks

MichaelG.

Thanks, Alan. That really is a very neat job.

5,237 rpm? Wow! Bearing in mind that the pulleys on the Mk 1 were set up to give a maximum 1,650, I've never taken mine much over 2,000; I thought the bearings might not stand it. Perhaps I should be more adventurous when using small cutters and drills.

Sorry to drag your thread off track, Ian.

Andy

Hi

Many thanks for the info received. My mill is the later type that uses 6mm round poly belt, heat joined.

Works ok at higher speeds, but when the lower speeds are used as Andy states, driven by a transfer gearing arrangement from the motor to the pulley, the drive will slip at very light cuts, 4 thou or so.

The suggestions of a poly vee belt look interesting, it may pay me to reduce the number of speeds and use a wider belt as the original pulleys are quite narrow.

reagrds

Ian

Hi

missed the post last month on belt drives as I was away on holiday.

Ian

Andyf

I have replaced the plain bearing at the base of the pulley with a ball bearing but have not yet run it for any length of time at the top speed possible so I would not take my theoretical max speeds as a reliable basis for design it is just that it is possible but for how long?

Regards

Alan

Edited By Alan Jackson on 20/10/2012 22:37:10

Alan, do you mean a thrust bearing between the underside of your pulley and the "lid" on the head casting? I hadn't thought of that, but it would be better than direct contact between the pulley (or in my case the underside of the aluminium epicyclic fearbox* casing) and the lid..

Andy

* a typo, but it does rather sum up my feelings about the thing.

Edited By Andyf on 21/10/2012 00:58:42

I use 6 mm round, heat joined belt on my Super Adept, and I think 5 mm , or even 4 mm would be adiquate for that, I'v got a 180W motor on it, think if you go the round belt way, 6 mm would be OK. Still like the idea of the Poly V belt. Ian S C

John A.S.

I have a centec 2a which has the same boby and drives as the 2B. I also suffered the same warming up experience as you describe. I came to the conclusion that the primary (motor to machine ) belt and the machine gears plus the lub oils caused the slow speed up particularly in winter when the motor cut out could be activated.

My solution was the fitting a seperate motor for the vertical head using a poly vee belt plus an inverter, I have not looked back. See my post under newton tesler title last year.

Regards Paul.

Paul - thanks for the interesting idea; MichaelG - thanks for the interesting link.

All things to think about, especially combining the VFD/sep. motor and the poly-vee belts...

Maybe after the Worden is finished!

Another JohnS.