Vee-belt pulleys

[cmhicks]

Hi All,

I've got a Seally drill press that has always vibrated quite a bit since new. It's vee-belt drive with a 5-step pulley on each of the motor and spindle. The motor run on its own is fine, and there doesn't seem to be any great amount of play in the spindle, so I suspect the vee-belt and pulleys.

The pulleys are die-cast aluminium, and I'm wondering how easy or otherwise it would be to true them up on the lathe, and whether I could expect quieter running of the drill as a result. Anyone done this?

Thanks in advance,

Christopher

[SteveW]

Christ,

I had a similar problem with vibration on my Myford 7B when I upped the primary vee belt to the faster pulley set. I described the problem to the Myford man and asked about a re-con kit for the lay shaft. He said it was the solid vee belt and sold me one of those multi-segmented belts saying it would solve all my problems.

I haven't had time to try it yet. Anyone else here tried this cure?

[spurley]

Hey Chris

Promotion!?!? ;D ;D

Cheers

Brian

[jackrae]

Before I bought a tesla system, I had vibration problems with my myford and cured it by changing to the "Brammer" type segmented belt. You have to ensure it's fitted the right way round, so's the inside tails of the links are trailing in the direction of movement.

Re the drill press, is it a 10 speed with an intermediate idler pulley or a simple 5 speed . If it uses a 10-speed arrangement you may find that the vibration is caused by the intermediate system "bouncing". On my old drill press I found that the position of the pulley, relative to the system geometry was quite critical. Again I used a section of linkede belt for one of the drives to cure most of the problem. Getting rid of the machine cured all the problem.

Even though your motor runs smoothly off-load, the chances are that its the motor quality that's causing the problem. Cheep single phase motors are notorious for "lectrical" vibration when on load. They may be mechanically balanced but they "notch" between poles due primarily to lack of steel and copper in their make-up.

regards

Jack
.

[Laurie_B]

jackrae said:

Before I bought a tesla system, I had vibration problems with my myford and cured it by changing to the "Brammer" type segmented belt. You have to ensure it's fitted the right way round, so's the inside tails of the links are trailing in the direction of movement.

That's interesting.The vee belt on my Myford is looking a bit frayed now,and I was thinking of fitting one of these Brammer type belts to save having to strip the headstock and countershaft assemblies.Could I ask where did you aquire your belt from ?

[jackrae]

Most of the usual bearing supply or pulley agents should be able to supply linked v-belts. Their cost/foot is a bit more than a normal v-belt but that simply reflects the extra work and material involved.

If my memory serves me right the Myford primary drive is an "M" section belt and the drive from layshaft to spindle is an "A" section.

Most of the common types can be easilyassembled/disassembled using pliers to rotate the link pins - make sure you get this type or you'll have difficulty making them the right size.
The belts also have a slight tendency to stretch after initial fitting as the links take up so be prepared to have to take a link out after a few hours use. However after this initial settling in period they are excellent for elimination of vibration.

Jack

[SteveW]

Laurie,

I got my primary belt from the Myford stand at the Guildford show at around 32 quid.

[houstonceng]

jackrae said:

Snip.

Cheep single phase motors are notorious for "lectrical" vibration when on load. They may be mechanically balanced but they "notch" between poles due primarily to lack of steel and copper in their make-up.

regards

Jack
.

All single pole motors "cog" (even expensive ones) it's in the nature of the beast.

[jackrae]

Andy,

The older style, when British industry built things to "Clyde" standard rather than price, had plent of meat in the rotor assembly with the resultant increase in inertia that effentively eliminated this cogging effect

You pays your money and you gets your goods

Jack

[houstonceng]

Jack

Sorry to say they all "cog". It just depends on "how much".

I have a British Thomson Houston (No relation) 1/2HP Induction Start and a 1/4hp BTH induction start single phase motor - both "pre-WWII". [BTH - later became "Hotpont"]. I also have a 1.5kW (2hp) Brook-Hanson (PKA Brook-Crompton) capacitor start single-phase motor circa 1997. They all exhibit classic "single phase pulsing".

None of these are "resiliantly mounted" and all are niminal 1450RPM and heavily constructed. The first one was salvaged from an "industrial sized" domestic washing and rotary ironing machine - made by BTH and called "The Hotpoint" - which my father bought new, circa 1938, and scrapped circa 1975. The effect wasn't noticable on the machine, but is when the motor is well loaded driving a machine.

The second was used on a vane compressor and currently is "in store". No effect was seen on the compressor.

The latter motor was replaced by a 3-phase on my lathe since it cause patterning on the workpiece when taking a light finishing cut. It's also "in store".

I will agree that the heavier the construction of the "squirrel cage" the more the flywheel effect, but nothing will effectively remove the "cogging"/"pulsing" entirely.

[Prowe]

Gentlemen
Slightly off the original topic, but I thought some might benefit from my experience. When I first inherited my Super 7 there was no way I could achieve a good finish when facing bar stock, surface finish when turning diameter was fine. I went through all the usual checks – tool grinding, surface speed, slide way adjustment etc. nothing made any difference.
I spoke to Myfords at one of the Midlands exhibitions and after seeing an example of the surface on a bar end, they assured me that it was due to incorrectly ground tool bits. To be fair they did later grind a piece of tool steel and send it to me F.O.C. but needless to say it made no difference.
On a colleague’s recommendation I replaced the drive belts with new ones and to my surprise all patterning on facing cuts disappeared. I have later learnt that this is not unknown especially where the lathe has been standing for a long period, which had been the case with my m/c; I presume the belts develop “flats” where they have been in contact with the pulleys and this sets up a vibration.
However the belt change on a Super 7 is not the easiest of tasks to undertake, so I really like the sound of the detachable link type of belt for anything in the future.

Regards to all,

Phil

[havoc]

On a colleague’s recommendation I replaced the drive belts with new ones and to my surprise all patterning on facing cuts disappeared. I have later learnt that this is not unknown especially where the lathe has been standing for a long period, which had been the case with my m/c; I presume the belts develop “flats” where they have been in contact with the pulleys and this sets up a vibration.

This is what my drill has. You can feel it when you turn the pulleys by hand. The belt has a "favorite position" where it gives more resistance.

[chris vine]

I too can say that the multi link belt for primary on super 7s makes a great difference for the better.

Chris.

[cmhicks]

Thanks for all the info regarding belts. I'll definitely try a segmented one (maybe on the lathe, too) before messing with the pulleys.

Christopher
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