bandsaw speed

[fobco]

hi chaps,me again,i have just got a dominion 14"bandsaw,its got a 4 pole motor,its a direct drive no belts,should it be a 4 or 2 pole,what sort of speed should a wood bandsaw run,thanks frank.

 

[9fingers]

Say 1000 to 3000 feet per minute

2pole motor runs at 2850 rpm on 50Hz, 4 pole , 1425 rpm.

HTH

Bob

 

[fobco]

hi bob,the 2 and 4 pole speeds i understand,but will a 4 pole be ok as a direct drive,or would the 2 pole be more adequate,frank

 

[9fingers]

4 pole will possibly give better starting for a given type of motor but if you make sure have a capacitor start and run type motor then you should not have any problems. I assume we are talking of single phase?

Surely getting the speed right from the direct drive is the most important thing here and that depends on the size of the driven bandwheel.

Bob

 

[Tony Spear]

hi bob,the 2 and 4 pole speeds i understand,but will a 4 pole be ok as a direct drive,or would the 2 pole be more adequate,frank

Bob has given you the blade speed you need to obtain i.e. 1 to 3 thousand feet per minute.

You can then establish which is the correct motor by measuring the pulleys that the blade runs around and calculating the peripheral speed.

i.e. pulley diameter in inches divided by 12, multiplied by 3.142 (pi), multiplied by motor rpm gives you the blade speed in ft/min.

The motor that gives you the nearest to Bob's figure is the right one.

e.g for 6" pulley
6/12 x 3.142 x 1425 = 2239 ft/min.
OR 6/12 x 3.142 x 2850 = 4477 ft/min.

So in this case 2 pole is too fast!

 

[9fingers]

hi bob,the 2 and 4 pole speeds i understand,but will a 4 pole be ok as a direct drive,or would the 2 pole be more adequate,frank

Bob has given you the blade speed you need to obtain i.e. 1 to 3 thousand feet per minute.

You can then establish which is the correct motor by measuring the pulleys that the blade runs around and calculating the peripheral speed.

i.e. pulley diameter in inches divided by 12, multiplied by 3.142 (pi), multiplied by motor rpm gives you the blade speed in ft/min.

The motor that gives you the nearest to Bob's figure is the right one.

e.g for 6" pulley
6/12 x 3.142 x 1425 = 2239 ft/min.
OR 6/12 x 3.142 x 2850 = 4477 ft/min.

So in this case 2 pole is too fast!

I can only hope this is a 3 wheel saw. Otherwise if it is a 2 -wheeler, being quoted as a 14" saw it would imply at least a 15" driven bandwheel so even a 4 pole motor will be too fast!

Bob

 

[Tony Spear]

You're dead right there Bob!

I've just looked at the VWM website and all the Dominion machines there seem to be 2 - wheel units.

The smallest I can see has a maximum cut of 370mm. and a wheel diameter of 410mm.

Have I made a boo-boo? :?

 

[fobco]

hi again chaps,the dominion i have has 14"wheels,its a very old machine,what bob and tony have said is all double dutch to me,well lads using yous calculus,what motor should it have 2 or 4 pole for good wood cutting,frank.

 

[9fingers]

Where precisely is your confusion Frank?

When you say direct drive, do you mean that one revolution of the motor shaft turns the driven band wheel one revolution?

One turn of a 14" bandwheel will advance the blade by 14/12 X pi feet= 3 feet 8"

if you have a 4 pole motor running at 1425 rpm then the blade will run at 5225 feet per minute.

If this is the case then it is too fast and maybe you should be looking at a 6 or 8 pole motor.

Bob

 

[devonwoody]

What does it cut like? :wink:

 

[fobco]

hi chaps,i will try and make it clearer,the motor is italian not brook as should be,being a old english machine,its not under power because the tyres were shot,but the lower wheel is bolted to a boss,which is original its reduced in the middle for 24mm with keyway,it would i assume it was 1" when made,so when the motor turns so does the wheel,a company called electro-motion have the same one for sale,but that has a 2 pole motor,very confusing,help frank.

 

[9fingers]

So this is the one you are looking at Frank? http://www.electromotion.co.uk/stockite ... item=47430

It does not say 2 pole motor in the advert but maybe you have talked to them.

Anyway back to your saw.

1) There is nothing wrong with Italian motors.

2) If it is 4 pole I still think that is going to be a bit fast but get it running and see how it cuts. If it is too fast then maybe look out for a 6 or 8 pole motor.

3) make sure that the bottom wheel runs true now that it appears someone has modified the bore. A small error there and the high speed could have the blade flying off.

4) There are other ways to get a reduced speed but I don't want to confuse you any more are this stage.

Despite what you seem to think - I am trying help - honest

Bob

 

[Tony Spear]

So this is the one you are looking at Frank? http://www.electromotion.co.uk/stockite ... item=47430

It does not say 2 pole motor in the advert but maybe you have talked to them.

Bob

But it does say 3 PHASE! :?

Maybe 'twould be useful to know what the rating plate for the existing motor actually says (even frame size would help) also is it foot, flange or foot/flange mounted? :?

 

[9fingers]

Tony,

Frank said it was 24mm shaft which suggests a 90 Frame size which also fits with a 1.1kW/1.5Hp motor as fitted to the one for sale on the website I found.
However I'm still concerned about the speed being too high.

If it were mine I would put on a 3 phase motor and run it from a speed controller. That is what I have on my startrite and with one belt change and an inverter I can do wood or 1/4" steel with ease.

Bob

 

[Tony Spear]

Tony,

Frank said it was 24mm shaft which suggests a 90 Frame size which also fits with a 1.1kW/1.5Hp motor as fitted to the one for sale on the website I found.
However I'm still concerned about the speed being too high.

If it were mine I would put on a 3 phase motor and run it from a speed controller. That is what I have on my startrite and with one belt change and an inverter I can do wood or 1/4" steel with ease.

Bob

Agreed.

If he's only got a single phase supply, can he get a combined transformer/frequency/phase converter?
I'm getting out of my depth here!

 

[Tony Spear]

Funnily enough Nev. Hallam has just posted this on the thread about his Wadkin AG 10.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 3D1&_rdc=1

Bit big for this requirement, but I assume you can get smaller? :?

Edited to correct typo's!

 

[9fingers]

Hi Tony,

I think Frank might have confused you as well as himself :lol:

My understanding that he has a saw which has had the motor swapped at some stage and it now has a 4 pole metric shaft motor on it. I asked if it was single phase and got no reply.

In trying to show us which model it is, he mentioned another similar one for sale by Electro Motion and I did a search and found the one I linked to.

Hope that clears it up for you!

Bob

 

[fobco]

hi bob,your 100% right,its 3 phase 1.1 kw 4 pole 90frame,i run my machines from a static convertor,i am not a single phase man,3 phase far better,i did email electro-motion and they said their one was 2 pole,very confusing,i cannot use mine under power as yet i striped the tyres off,waiting for new ones,frank.