P-Power hacksaw

[Chris BaetensParticipant @chrisbaetens16442]

Some more pictures while cannibalizing it even more.
Two brushes are angled at 180° and a third one is angled at (about) 60°.
So that explains it about the two different speeds I suppose.

[Ian PParticipant @ianp]

Well it is definitely a two speed motor. For your application the motor will be best on the slow (180 degree) brushes.

Can I suggest you undo the brush carrier plate and lift it slightly to see which wire goes where (or whether there are any other bits lurking)

Strange that the self parking mechanism is not apparent. Maybe on modern cars its done with an optical sensor on the blade mechanism.

The other oddity is that in order to stop the wipers dead in the parked position the usual method is to short out the motor. This would be done on the 180 degree brushes regardless of what speed the motor was running at. The is shorting might nowadays be done by whatever electronics is controlling the motor.

Ian P

[John RuddParticipant @johnrudd16576]

Posted by Chris Baetens on 20/04/2017 08:22:22:

Some more pictures while cannibalizing it even more.
Two brushes are angled at 180° and a third one is angled at (about) 60°.
So that explains it about the two different speeds I suppose.

I did mention this previously about the motor having two speeds…….obviously missed by many I guess….

If you connected your supply directly to the two wires rather than one wire and the casing, it will make the motor run hot!

"Have you considered that the motor may be a two speed job?

The negative connected to the body of the motor and the positive connected to one of the two wires for the two speeds?

Ordinarily, the brushes would  be opposite each other with half of the armature connected across the supply, with a third brush contacting a reduced number of coils, would give a higher speed but an increase in current….."

Edited By John Rudd on 20/04/2017 09:23:01

[Chris BaetensParticipant @chrisbaetens16442]

No no I didnt miss it at all John, that's why in the end I disassembeled it. Thanks for the tip..!

In the second picture of the last post the yellow lead(on the right) is 180° sepparated with the "-" lead(far left) and result in the higher speed. The 60° brush(center in the picture), connected to the white lead gives me the slower speed.

[Ian PParticipant @ianp]

So now we have a third wire! (originally you said there were two wires coming from the motor)

So white and yellow go direct to brushholders, what is the third brush connected to, and what is the third wire connected to?

Ian P

[Ian PParticipant @ianp]

Earlier you mentioned the possible difficulty of attaching a crank to the tapered and splined shaft. What I have done is created a taper hole (I used a hand taper reamer) that is somewhere near the right size and used the nut to pull the part up very tight to 'bed' the splines. As you are only adding a single crank the precise alignment is not critical if the crank does not pull up dead square. My crankpin was a ball joint which give a lot of leeway.

If you add locking compound into the equation it will be more than strong enough as the end result will be limited by the plastic gear on the shaft.

Ian P

[Chris BaetensParticipant @chrisbaetens16442]

Basically there are two wires that go to the brushes (yellow/white). The third one is the one I added and is connected to the outside of the casing. That's the black one in the picture.

If you look closely at the last picture, you'll see that the left brush is connected directly to the casing(with a screw) The brush on the right is connected to the yellow lead via a connecting-nippel
Sorry if I was not clear the first time…

[Chris BaetensParticipant @chrisbaetens16442]

This is my old hacksaw that will be replaced. Like I said before it takes up to many space in my workshop.
On the far right you'll notice a windscreen-wiper-motor. That one is getting hot to.
This saw runs at 60rpm, I'd like to speed up the new one a bit. I'm aiming at 80 maybe 100 rpm

In the vise a 50mm -2"- brass rod.

[John RuddParticipant @johnrudd16576]

Posted by Ian Phillips on 20/04/2017 09:47:04:

So now we have a third wire! (originally you said there were two wires coming from the motor)

So white and yellow go direct to brushholders, what is the third brush connected to, and what is the third wire connected to?

Ian P

There are three brushes……there are two wires.

Two wires go to two brushes.

The third brush is connected to the motor casing= 3rd wire….

[Chris BaetensParticipant @chrisbaetens16442]

Posted by John Rudd on 20/04/2017 10:25:56:

Posted by Ian Phillips on 20/04/2017 09:47:04:

So now we have a third wire! (originally you said there were two wires coming from the motor)

So white and yellow go direct to brushholders, what is the third brush connected to, and what is the third wire connected to?

Ian P

There are three brushes……there are two wires.

Two wires go to two brushes.

The third brush is connected to the motor casing= 3rd wire….

That covers it even better, thanks John.
In my post at 10:00:03 I should have added : The second wire(white) is connected to the most upper brush in the picture(barely visible)

Thanks again John..

[Chris BaetensParticipant @chrisbaetens16442]

Yesterday I was parting of a thick piece of brass with my old power hacksaw. For some reason my saw got stuck without me noticing it. It stayed blocked for an estimate 1.5 hours. Entering my workshop after that amount of time I immediately was alarmed by the unmistakable smell of burned electronics.
To make a long story short. Powerunit was not working anymore and was rather hot. The windscreen-wiper-motor was boiling hot. So that was the end of it, lucky me I was planning to make a new one. And lucky me that nothing worse had happened.
Next day al was cooled down and I thought why not, lets try that thing and see what happens. Guess what, if as nothing had happened the day before, that hacksaw started to work again. And what's more I used the same (computer)powerunit to power that hacksaw. Big surprise, that was absolutely not what I expected.

Point of this story : No need to be afraid anymore; windscreen-wiper-motors can handle this kind of abuse…

[Chris BaetensParticipant @chrisbaetens16442]

Ok, almost done drawing.
I'm trying to add a solution to wear out the complete length of the saw.
Three options : relocating the part by adding a dummie part or a piece of wood in the vise(That's what I'm doing now). Second I could relocate the vise. And third I could mount the saw reversed in it's holder so the sawing action is in the other direction.
Other ideas ..?

[Martin ConnellyParticipant @martinconnelly55370]

Only cut big parts

Martin C

[Chris BaetensParticipant @chrisbaetens16442]

Posted by Martin Connelly on 02/05/2017 14:04:03:

Only cut big parts

Martin C

Why didn't I think of that simple solution, silly me…

[Ian S CParticipant @iansc]

Or do as I id on my little one, the vice is held down by two bolts and they go through the bed via a long slot so that the vice can be slid along so that the full length of the blade can be used.

Ian S C

[Chris BaetensParticipant @chrisbaetens16442]

That was one of my ideas to,

Thanks Ian.

[Nick HulmeParticipant @nickhulme30114]

Posted by Chris Baetens on 02/05/2017 21:25:54:

That was one of my ideas to,

Thanks Ian.

"Rapidor Manchester" Power Hacksaws also have a movable fixed jaw to allow appropriate positioning of work within the stroke of the blade, the blade jaws can be set for angles too,

– Nick

[Author]

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