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Variable Speed Bench Sander Conversion

View attachment 497713

(with thanks to @MrBane for the use of his avatar)

Dear Mr @moderator

I love informative posts, sadly yours falls short on information

You'd best have a word with Hoover as a diode in series is how they added Low & High speed to vacuum cleaners. Obviously Hoover must be wrong and BS/EU Safety Standards wrong too

What's that? Oh, it's crickets

Rgds

That's a direct drive induction motor, so mechanical schemes are out. To change the speed of induction motors, you really want to change the frequency, but that's not going to be cheap. You could change the applied voltage, like @pcar964's suggestion, but that's a) going to fvxk with the start capacitor and b) still a pain in the arrse.

Afaik diode is used to half the frequency, lower total implied DC voltage is a less important aspect

 
I have a Clarke brand bench sander/disc sander combo thing. TBH, it's pretty pants, but it's what I have and I can't afford to replace it with a decent one - I spent all my cash on a professional lathe.

This POS machine has a simple on/off button. Much of the wood I use burns at the speed this thing runs at. Can anyone tell me how to take the thing apart and convert it from the on/off button to a variable speed controller. I'm no electrician, but I know how to do the basics of electrikery.


Oh, and never, ever by 'Clarke' branded stuff. It's crap.

1. Coarser belt.

2. Press harder.
 
Dear Mr @moderator

I love informative posts, sadly yours falls short on information

You'd best have a word with Hoover as a diode in series is how they added Low & High speed to vacuum cleaners. Obviously Hoover must be wrong and BS/EU Safety Standards wrong too

What's that? Oh, it's crickets

Rgds



Afaik diode is used to half the frequency, lower total implied DC voltage is a less important aspect

Believe it or not... it wasn’t intended to be informative. I have no need to have a word with Hoover or anybody else. May I suggest you remove your head from the extreme depths of your humourless arse.

Rgds.
 
Dear Mr @moderator

I love informative posts, sadly yours falls short on information

You'd best have a word with Hoover as a diode in series is how they added Low & High speed to vacuum cleaners. Obviously Hoover must be wrong and BS/EU Safety Standards wrong too

What's that? Oh, it's crickets

Rgds



Afaik diode is used to half the frequency, lower total implied DC voltage is a less important aspect


Half-wave rectified AC I suppose would indeed half the frequency of the applied voltage (and the voltage too), but I am not sure what effect that would have on an induction motor. I suspect the starting capacitor wouldn't charge properly, and might not start at all.
 
Believe it or not... it wasn’t intended to be informative. I have no need to have a word with Hoover or anybody else. May I suggest you remove your head from the extreme depths of your humourless arse

Excuses, excuses. You put it up to say I was talking dangerous bollocks

If you don't know what you're talking about, best to be silent rather than reveal you're a fool
 
Half-wave rectified AC I suppose would indeed half the frequency of the applied voltage (and the voltage too), but I am not sure what effect that would have on an induction motor. I suspect the starting capacitor wouldn't charge properly, and might not start at all.

Don't know, elec motors are not my area, but would have thought it will charge albeit milli-seconds slower. It worked for Hoover and it's worked for me on various loads.

Give it a go, cost is pennies

I discovered the Hoover diode when Vac went full speed even on low and I took apart - On/Off fed 3 pin Low/Hi switch diode on 'Lo' pin. Replaced it with higher rated and all fine and thought "what a great, simple idea"
 
Excuses, excuses. You put it up to say I was talking dangerous bollocks

If you don't know what you're talking about, best to be silent rather than reveal you're a fool
You really are a cock. Until now I had only thought you might be. You perhaps do well to follow your own advice.

Oh... If I’d thought you were talking dangerous bollocks, then believe me, I’d have told you so quite bluntly. As it was it was just bollocks. Now be a good chap and do one, there’s a good halfwit.
 
My oh my. A BOGOF post

You really are a cock. Until now I had only thought you might be. You perhaps do well to follow your own advice.

Projection in full swing

Oh... If I’d thought you were talking dangerous bollocks, then believe me, I’d have told you so quite bluntly. As it was it was just bollocks. Now be a good chap and do one, there’s a good halfwit.

Rabbit holing there as there as diode already proven as a widely used solution

Are you Harry?
 
Why would Clarke produce a belt sander with the wrong rpm, they are not high quality but they have been importing machinery for a long time.

Its more likely the OP is using it wrong.
 

Legs

ADC
Book Reviewer
Why would Clarke produce a belt sander with the wrong rpm, they are not high quality but they have been importing machinery for a long time.

Its more likely the OP is using it wrong.

I am most certainly not "using it wrong". I do actually know what I am doing with the tools I own and use very regularly. I have in fact been using this machine for the last six years. I also did not say that it was produced with the wrong RPM. I said that for much of the wood I use it is too fast. It is made for basic woods, like Pine, Oak and suchlike. Some of the very dense 'exotic' woods are not happy being sanded at high speed, so they burn very quickly.

I want a bench sander that I can use at much lower speeds. Speeds that will not burn the woods that I wish to use it for. Stop making assumptions.
 
Don't know, elec motors are not my area, but would have thought it will charge albeit milli-seconds slower. It worked for Hoover and it's worked for me on various loads.

Give it a go, cost is pennies

I discovered the Hoover diode when Vac went full speed even on low and I took apart - On/Off fed 3 pin Low/Hi switch diode on 'Lo' pin. Replaced it with higher rated and all fine and thought "what a great, simple idea"

They’re different kinds of motors. A vacuum cleaner will use a universal motor, that belt sander has an induction motor. Three phase induction motors will self start due to the different erm, phases of the induced fields. Single phase induction motors (such as we’re taking of here) require a start capacitor. That produces a secondary magnetic field that is not in phase with the supply, and thus starts the motor. It will be switched out once the motor is running. If it doesn’t charge enough to produce a strong enough field, the motor won’t start. Cutting the applied voltage to 50% of its rated value, while also effectively DC biassing it with a diode is at best going to be unpredictable, and at worst may damage the motor (due to the heating effect of the DC bias).

It works on a universal motor because the two opposed electromagnetic poles are still there, just smaller field strength.

As for giving it a go, er, no thanks. The machines I want to be variable speed are already variable speed using completely different methods.
 

theoriginalphantom

MIA
Book Reviewer
petrol
match
insurance
 

Troy

LE
1. Disconnect electric motor.
2. Fit hand crank*


* Optional alternative is to mount the sander on Grannie's old treadle sewing machine table and power it by foot.
 

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