Parkanson Power Hacksaw

For no logical reason my immediate reaction was that it is turning the wrong way! My wife made the predictable response to that.

Love Bluey's signature line!

Henry

Na rijp beraad schreef Dragon :

I agree..! Made a small power hacksaw myself. One can really feel the downward pull during the back stroke if the motor turns the right way.

When I first started it the motor was running in the anticlockwise direction and the drive gear on the machine was very noisy . I thought that the motor should spin in a clockwise direction and the electrician agreed with me .(He says in his experience normally an electric motor runs in a clockwise direction.) Not being electrically minded I had no idea really which way it was supposed to turn , just thought it was too noisy . He changed the direction of the motor and it quietened down significantly.

just do what i did ..

time it cutting a peice of metal ..in both directions

the quickest time is the right direct .

all the best.markj

What is clockwise on an electric motor? It's obvious on a clock because you only view it from the front, but there is no front or back to an electric motor.

Cliff Coggin.

I would have thought looking at the shaft end that has the pulley mounted on it. Thats how we viewed it anyway. Not much point looking at the end that has only the cover and no shaft protruding .

Regardless which way it runs the machine works and I've been slicing up

That sounds reasonable. I just wondered if there was some sort of convention for describing motor rotation. All the motors I saw in industry had the output shaft enclosed and invisible, so we looked at the cooling fan at the opposite end, which naturally would appear to be running in the opposite direction to the way you describe.

Cliff.

I guess you can look at it like that ,I can see the cooling fan on the end of my motor through the grill so you are right ,looking at it from that end.

My pocket watch opens from both sides ,but I can ony read the time from one side ,but I can see the workings from both sides.Similar thing I reckon.

Yes,there is.It is when looking on the drive end,or DE.

I timed it at it's current rotation , I will see if I can collar the electrician tomorrow and change the motor rotation and try it again. Took 12 min 26secs to cut through a piece of 100 x 25 mm mild steel bar on the flat at the lowest feed setting .

Am I missing something here - surely as it reciprocates using a crank the cutting rate will be the same whatever way the motor rotates as the saw 'strokes per minute' will be the same.

AWEM

Say the blade is set for cutting backwards, the back stroke is doing the actual cutting. Look at the angle of the crank on the video. As the crank pin circles, it pulls the crank (and so the blade) down to assist the cutting action. On the return stroke the blade is pushed upwards. Hope this helps.

It's quite a short linkage, so will tend to lift or pull down the end of the saw blade. It may be better for the blade to be pulled down on the cutting stroke.

Thanks Mark.

Cliff.

I would have thought that you would be much quicker cutting on the vertical not the flat. Thats what I do with my cold saw. Definitely agree that the motor should run so that the crank assists in pulling the blade back and "down". Ensure blade put in with teeth pointing back though

Richard

It rotates the same way as my Wicksteed saw so I think you have the rotation correct.

My Wicksteed cuts on the pull stroke. It has a complicated hydraulic pump that performs about three functions - the one concerning us here is the function that raises the blade a tad on the return (forward) stroke. I initially wired my motor backwards and the saw still cut in a fashion, but I was able to detect visually that the timing was out and the lifting of the blade wasn't occurring at the correct time.

Has yours got two speeds like mine?

Julian.

I tend to agree with your comment , now that It has been brought to my attention . I think the crank arm should be at the bottom of the crank wheel on the backward stroke , that way the arm would be in a horizontal plane when pulling the bow rear ward.

Richard , To answer the point about cutting on the flat or on the widest side of the metal , I feel it's better to have more teeth doing the work than to have a few doing the work , probably may cut faster , but the blade would tend to wander off the vertical because there is less support from the material being cut and blade life would be reduced. Ive always done this with saws the more teeth sharing the load the better.

In my experience ,saws of this type cut on the back stroke (there probably are exceptions) , towards the fixed side of the vice ,it's cutting on the backstroke now ,change of rotation hopefully will not change this.

I'll get the rotation changed and see what the outcome is . Cheers

Hi Julian , Yes ,the Parkanson is two speed via vee belt drive from the motor . It has two pistons that are driven on eccentrics from the main drive shaft .The timing is correct at the moment , but I need to check with the opposite rotation ,IIRC it didn't look right when the motor was rotating in the other direction ,but then I was busy getting over the excitement of the machine working first time with out any major problems.I was more concerned with the noise the drive gear was making . .