Machine Belting

[Uzzy]

I know this maybe a stupid question but, I think I have inadvertently thrown away the belt for my milling machine the question is can I use a normal fan belt from a vehicle and if so how would I work out what size I require?

Happy New Year

[houstonceng]

Automotive fan-belts are not the same profile as machine belts but, depending on the profile of the pulleys on your M/C may drive it. The problem is that automotive belts tend to ride lower in M/C pulleys and can rest on the core diameter so that the wedging action is lost - consequence - belt slips, wears and so on in an ever increasing problem.

Back when I was experimenting with my lathe drive, I tried some car belts. Good for trial but not for serious long-term use. I also had to buy a new pulley for the replacement 3-phase motor I'm now goinfg to fit as a result of the experiments and found that the original far-eastern pulley on the single-phase motor was probably not the right profile for a M/C belt anyway.

As far as sizing goes, I haven't - so far - found a formulea on the www. It's obvious that it depends on the diameter of the pulleys, their distance apart and the belt profile. Then it's a case of working out the tangential distances between the pulleys.

In the end, I went to "5-way Belts and Bearings" (on the A20 near me) and he was kind enough to source a correct profile pulley and give me advice on belts. On a previous occasion, I needed new belts for my Warco-A1S milling M/C and took along the worn originals. It transpired that these weren't accurately described in size, so "Mr 5-way" lent me 4 belts about the right sizes and I was able to find a combination of two that fitted and returned the unused ones. Only then did he ask to be paid. He's very trusting !

Maybe, armed with some dimensions and a pulley, you could go to "5-way" and have a chat.

Meanwhile, if I find some of the info O have on belts, I'll e-mail it off-line.

Happy New Year

[houstonceng]

BTW Guys. This is the URL for "5-ways" - no connexion just a very satisfied customer glad to find a specialist who is willing to deal with non-industrial customers. I believe he has a minimum charge on line with most specialist suppliers these days.

www.fiveways-bearings.co.uk/

Andy

[waggy]

Uzzy,

The more I think about this the more I'm sure the belt length is nothing to do with the speed of the drive, the length is based on the diameter and centres of the pulleys.
The speed of the driven pulley(s) depends on the driving pulley size and speed it is driven, the same amount of belt length will run past the pulley(s), irrespective of length.
Try to use the shortest length you can to avoid long stretches of belt without any form of guide as vibration can be set up and belts can jump off pulleys due to vibration. A long length can be tamed by use of a jockey pulley or bearing that can act as a tensioner and vibration damper.

Waggy.

p.s. Bet you get some funny looks in the spare shops when you start measuring belts! Bad enough when you compare paint sprays and try to explain things other than cars can be painted too!

[Laurie_B]

You could always have a look at www.chronos.ltd.uk/acatalog/ as they supply a range of 'A' section drive belts.Click on 'Site Map' then 'Lathe Accessories' then 'Pullies and Belts'
They also sell 'A' section 'Powertwist' drive belt which looks like a linked system whereby anyone can make up whatever length of drive belt they require.
It looks handy stuff as I'm thinking of trying some on my Myford lathe when the drive belt eventually fails.Could save having to strip the mandrel and countershaft.

[houstonceng]

Waggy

You're correct. The belt length has nothing to do with the speed and is only a function of the belt profile, the distance centre-to-centre of the pulleys and their diameters.

However, the belt profile and number of belts used depends on the power to be transmitted and, since power is a function of torque and RPM, the RPM of the smallest pulley affects the belt type required. In addition, the actual size of the pulleys also dictates the type of belt and visa versa.

The more I looked into the subject - and discussed it with "5-ways" - I came to realise the depth of knowledge required. The original pulley on my lathe motor was, as far as I can assertain, too small for the "A" profile belt and actually an agricultural type. I bought a good quality taper-lock pulley and bush and an "A" belt rides lower in it.

BTW. It's the "PCD" of the pulleys that dictates the "gear ratio" and manufacturers list this with OD. The portion of the belt inside the "PCD" has to compress so some belts are notched to allow a tighter radius of use.

[Phil Sutton]

Hi.I should imagine belt thickness will also play it's part.I was just thinking that a slightly wider belt wouldn't ride so deep in the pulleys so would drive onthe edges.
I can remember as an apprentice,there was a large planer at work,the bed was about 6'x20',and was driven by a 25 (or was it 50?) horse motor,with a reverse operated by an electro-magnetic clutch...a monstrous great thing it was.This was driven by flat belting,and eventually it was decidedto change to V belts.These,along with a taper lock pulley & bush were obtained from Fenners,in Leicester.These wer fitted and the thing ran quieter and with no slipping worth speaking about even though the drive was still onto the original flat pulley which drove the machine(ie V belt pulley on motor,flat pulley on planer)
It was worth watching the clutch in operation,you could hardly see the movment,just like an epicyclic gear box....
Of course,it all went for scrap,when the place shut down,a year or two after I left.A shame really,some of the old Victorian and Edwardian machinery was really well worked out,and lasted and lasted..


Phil

[steamjohn248]

You might also consider using "Redthane"its basically a round section of some sort of plastic which will stretch but not very much. it never seems to wear and provided you get the right diameter for the pulley section so it does'nt bottom in the groove does'nt seem to slip. You simply buy a length slightly longer that the distance round the pulleys (measured with a bit of string, put it round where it wants to go, mark it for length, cut it with a knife a bit shorter than the mark, to give it some tension, poke the ally joiner into the hole in the middle one end
put it in place but off the pulley, push the joiner into the hole in the other end stretch it into the two grooves and off you go. No need to dismantle anything. We use it on boats a lot. bilge water, grease, oil, and all the other nasties found in boat engine rooms don't seem to bother it.

On the subject of service, anyone in Essex area smight try Essex Bearings and Transmissions near Maldon. same sort of mind set as 5 Ways. "Try those , if they dont work bring em back and you can try something different, pay when you get it sorted". They recently got me two rather obscure size and very tiny 'O' rings 'next day'. Two men and their Ladies bought the firm when their employers went bust and they survive by dint ofexcellent service. No conection other that a regular and very satisfied customer.

John

[Uzzy]

Thanks for all your advice I have had another rumage in the workshop and found what I think is the correct one.