Thread: Parkanson power hacksaw

Dave ,
when mine was cutting on the back stroke the connecting rod was at the top of the crank wheel and rotating in an a clock wise direction looking from the right side of the machine ,it was tending to lift the bow up as it pulled back .
When I had the motor reversed on the saw was cutting on the forward stroke the crank arm was at the bottom of the crank wheel and the crank arm was pushing the bow in a direct line ,as it should .
If you search the forum for my posts on the hacksaw and look at the video on U tube you can see how it was working before I changed the direction of rotation.
The single phase motor I got for my saw came from Royce Cross in Adelaide , I got a 3hp because the original 3ph was 3 hp .
Not having any electrical knowledge at all Im not sure if all single phase motors can be reversed .
IIRC I paid $230 for the motor plus 50 delivery , It was one of his recon motors ,I haven't had any issues at all with it.
this is the motor ,but as I said mine was a reconditioned one .
Royce Cross Australia -[ProductCodeID]=SB4CREMX

Kev

Hi Kev,

I think this is yours, before the motor was reversed.

[ame=http://www.youtube.com/watch?v=ZSV2O7-Stnk]Restored Parkanson Power Hacksaw - YouTube[/ame]

I can understand what Phil was talking about being anti-clockwise rather than clockwise.

Regards
Ray

Hi Kev
Are you saying that when you reversed the motor direction to anti clockwise it cut quicker than when you turned the blade around so the teeth were pointing at the motor but with the crank still running anticlockwise. Also isnt the headframe lifted by a dash pot type setup on the forward stroke.

Phil

Originally Posted by RayG

I can understand what Phil was talking about being anti-clockwise rather than clockwise.

Hi ray
I don't explain things too well. What I meant was if you were standing on the side the blade is on and were looking at the crank it should turn anti clockwise
Hope this helps

Phil

Originally Posted by Steamwhisperer

Hi ray
I don't explain things too well. What I meant was if you were standing on the side the blade is on and were looking at the crank it should turn anti clockwise
Hope this helps

Phil

Yes that's it..... I think.... ... so, the motor should run anti-clockwise and the crank should be at the top on the forward stroke, with the blade around so it's cutting on the forward stroke..

In the video, it's running backwards and the blade is reversed as well.. Kev's since reversed the motor and swapped the blade around..

Regards
Ray

Hi Kev,
Is the "power up" height adjustable?



Hi Phil
What you explained is what I was trying to get at in my last post.
But if you changed the timing on the lift cam 180deg wouldn't that let you cut towards the vice with the conrod in the correct position?
I can only think of two not so good reasons why they wanted to push. 1. the swarf 2. the work piece falls off towards the front of the machine and not back against the wall.

Stuart

Originally Posted by RayG

Yes that's it..... I think.... ... so, the motor should run anti-clockwise and the crank should be at the top on the forward stroke, with the blade around so it's cutting on the forward stroke..

Regards
Ray

Yes Ray but with the blade around so it is cutting on the back stroke

Originally Posted by Stustoys

Hi Phil
What you explained is what I was trying to get at in my last post.
But if you changed the timing on the lift cam 180deg wouldn't that let you cut towards the vice with the conrod in the correct position?
I can only think of two not so good reasons why they wanted to push. 1. the swarf 2. the work piece falls off towards the front of the machine and not back against the wall.

Stuart

Hi Stuart
You won't be changing the lift cam just the direction of the crank. The lift cam timing will be in the same position.
Cranks in this situation like to be pulled under load rather than pushed. It's about compression and tension on conrods.

Phil

Originally Posted by Steamwhisperer

You won't be changing the lift cam just the direction of the crank. The lift cam timing will be in the same position.
Cranks in this situation like to be pulled under load rather than pushed. It's about compression and tension on conrods.

Hi Phil,
If you just reverse the hacksaw in the video Ray posted won't it will be cutting on the push stroke? So you have to change the timing to make it cut on the back stroke.

Yes I like the conrod in tension as well, but they must have had their reasons.

Stuart

Originally Posted by Stustoys

Hi Phil,
If you just reverse the hacksaw in the video Ray posted won't it will be cutting on the push stroke? So you have to change the timing to make it cut on the back stroke.

Yes I like the conrod in tension as well, but they must have had their reasons.

Stuart

No
The lift cam comes into play at the end of the stroke. Whether the conrod moves upward or downward the blade will move forward. If the lift cam works on the forward stroke then it has to cut on the back stroke. Anti clockwise will keep the conrod in tension rather than compression when under load
lol like I said Stuart I couldn't explain things to save myself.

Phil

Originally Posted by Steamwhisperer

Hi Kev
Are you saying that when you reversed the motor direction to anti clockwise it cut quicker than when you turned the blade around so the teeth were pointing at the motor but with the crank still running anticlockwise. Also isnt the headframe lifted by a dash pot type setup on the forward stroke.

Phil

Phil ,
when I reversed the motor the crank was at the bottom of the crank wheel ,with the wheel rotating in a anti clock wise direction , this put the crank arm in a direct straight line with the blade .I had a image of a drawing I did explaining the difference but I must have deleted it .
I'm sure it's in one of the previous power hacksaw posts . But I cant find it.
The lift timing doesn't change with the reversed rotation direction.At least it didn't on my machine. I made sure and kept the sparky there until I was totally satisfied.
Just cost me a few more beers.
Kev.

Edit : I"m getting confused here trying to answer all the posts at once LOL.
And I got that wrong above .
The crank is still at the top of the crank wheel when cutting on the forward stroke ,but due to the rotation is pushing downwards toward the bow. (compression)
Whereas in the other direction the crank is pulling the bow upwards like in the video. (tension)
Timing of the lift remained the same , I didn't adjust that at all .

The lift height at the end of cutting when the beam is going up to the stop position is not adjustable with out some modification.Another notch could be cut in the locking bar and the auto stop lever adjusted so the machine is switched of at a lower height ,but the angle of the lock bar would have to be changed I think.

Worse thing is I haven't come up with a length stop and its a fiddle trying to cut stock to a exact length ,its hard to get it lined up with the beam way up in the clouds , and trying to do it with the beam down is a muscle building exercise.Trying to hold the beam up, adjust the stock to the blade and do the vice up is a struggle .Im thinking of a small indicator /length gage on the fixed jaw that shows the distance from the vice jaw to the blade so Ican line up a scribed line on the stock with the blade with out having the beam down.
Kev.

Originally Posted by Steamwhisperer

No
The lift cam comes into play at the end of the stroke. Whether the conrod moves upward or downward the blade will move forward. If the lift cam works on the forward stroke then it has to cut on the back stroke. Anti clockwise will keep the conrod in tension rather than compression when under load
lol like I said Stuart I couldn't explain things to save myself.

Phil

If you look at the video, the arm is down when the conrod is on the top half of the gear.(in the video in tension, running clockwise). The arm is lifted when the conrod is on the bottom half of the gear(compression). If you reverse the motor, isn't the arm is still going to be lifted when the conrod is on the bottom have of the gear, which is when you want the arm down?

Stuart

Originally Posted by RayG

Yes that's it..... I think.... ... so, the motor should run anti-clockwise and the crank should be at the top on the forward stroke, with the blade around so it's cutting on the forward stroke..

In the video, it's running backwards and the blade is reversed as well.. Kev's since reversed the motor and swapped the blade around..

Regards
Ray

Yes Ray that's correct .
edit added image

Kev

You mean to tell me it's still there at that price?

Dave

it sure is, thought it would be gone by now but i guess not hahah

Cooper