hacksaw hydraulic ram lifter - how does it work?

Hi all,

Seeking help in some reparations here.

I am in the process of bringing a Hercus power hacksaw back to life - I think it has been beyond use for many years and it is amazing that is has not yet seen the scrapper . Made in Australia and likely some time between 1938-1945 or so. This old girl::



The ram lifter mechanism does not work and I suspect some part(s) were missing when I got it. It is a very simple machine so I am figuring/hoping Hercus likely just copied or used a similar mechanism to other hacksaws of the period.

The lifter is to raise the ram on the non-cutting stroke during operation, but also it has to permit manual lifting of the ram for workpiece placement plus gradual lowering to the workpiece and also during cutting.

I'm only allowed 5 pics here so this initial post might go into the next post so I get get some pics in.



The unit is driven from an eccentric on the main shaft. It has two cylinders joined by channel. The small cylinder piston is attached to the shaft eccentric. The large cylinder piston is attached to the ram. Both pistons are plain - no rings or such. It has a brass 'valve' (?) thingo at the base. The small cylinder appears to have a bleed hole or something about half way up. The brass 'valve' appears to have some small holes or something at the top.

The hole in the 'valve' is pretty big. Way too big to permit any hydraulic action on the big piston - oil just goes in and out of the hole and the big piston never moves. I've tried oils ISO 68 up to ISO 140 differential oil. No joy.

I've tried quite a few experiments including the obvious 'put a ball bearing in the valve'. But this permit *no* oil to escape so if you raise the ram - it doesn't lower. "but what about the bleed hole on the small cylinder" - well, it seems to be always obscured by the piston. Even all full 'extension' with the small piston as far out as it will go - including all adjustibility, that hole is still covered. So .. no oil out.

The holes in the top of the 'valve' seem functional - like that are supposed to hold something in .. or something sat on top and oil bled through these holes underneath it. Dunno.

Anybody know how a unit like this is supposed to wok? It is driving me nuts!

All help appreciated,

Greg.

The system is a plunger pump ,a lift cylinder and a bleed screw......first ,fix all the packing glands and piston buckets......glands will be asbestos string,buckets ,leather........the fluid is coolant mix of water and soluble oil......having got the unit pumping,the motor must be running the right way,or the lift and fall will be timed wrong.......there is generally a weight to counterbalance the cut force,and avoid stripping the blade.

Most of the time they don't work ! Did my disc lifting the arm on one. I was working in a school were the saw was positioned right next to a wall so you couldn't get at the mechanism to repair it. It just felt like a hot stiletto had been shoved into my back. I came out with a right mouthful. There was a kid stood next to me ! I said " You didn't hear that did you son ? "


Regards Tyrone

OK,......first ,do you know F.W.Hercus is still in business,the saw is a lot more modern than you think,and Hercus' may have a PDF of a parts and assy drawing...Second,the pump works on soluble oil coolant......and the setup will also supply coolant to the cutting area.Its a simple plunger pump ,and the ball valves should be arranged accordingly.There should be a bleed screw that restricts the flow to lift the blade assy.The weight also needs to set correctly for cutting pressure.These saws work quite well in use,and are a quality product...and Hercus is a quality maker.Oil the bearings and slides when its working.....And the motor must run the correct way......Edit.....as the thing is working the blade assy rises and falls with the eccentric action,rises on the back stroke,falls on the cut stroke.Note...the blade teeth must also point in the correct direction to cut.To operate,(assume bleed is closed),as the blade goes back and forth ,release the bleed screw enough to give the rate of downfeed consistent with easy cutting.....If you cant figure a simple mechanism,you will never be an engineer ,machinist or fitter.

John/Tyrone - thanks.

Tyrone - sorry to hear about your back mate!

John, there is no bleed screw as such. The slotted screw in the side has no hole or adjustability - Actually, I am not sure what its true purpose it. It just seems to be a screw with a well-define taper and matching taper on the pump. And the way it fits makes me think it is original. I did have a thought that it was not original and maybe that's were the bleed screw originally went. The only 'bleedy' looking thing is the hole half-way up the front cylinder - and it is always obscured by the piston.

The unit had no 'packing glands' in it - I'm not sure it uses any (and not quite sure what one is!) , but I could be wrong - but the pistons are pretty ordinary items - this is the vertical:



Do they commonly have some sealing mechanism beyond a good sliding fit?

The hacksaw has a separate coolant pump/reservior to this pump/reservoir so I suspect (and confirmed by another Hercus hacksaw owner - that has never had the pump apart) that ISO 68 hydraulic oil is the go. If you look at the pic of the machine in the first post you can see the coolant pump/reservoir underneath the machine.

Re Hercus still being in business - funny ... I didn't know that. I'll ping them an email. Nice. Re the saw being modern, I am pretty sure it is of the late 30's early 40's era. They changed the main pulley later and then made it geared - so these big 'steam wheel' pulley are of that era.




Thanks again

I used to own a similar antique power hacksaw. The pump cylinder and lift cylinder were connected by an open passage.

There was a ball that served as an inlet check valve that allowed oil to enter the system (from the reservoir) when the arm was raised manually .

There were no seals or packing on the pistons.

The entire pump/ram assembly was submerged in the oil reservoir.

To lower the arm, the operator could pull on a lever that unseated the inlet check valve.

My machine was old and worn. The lift ram leaked down quickly enough ( past the non- existent seals ) that it was not necessary to use the lowering lever.

There was no adjustment for feed rate, other than a sliding weight.

Now that I think of it, the "lowering lever" was not a lever but actually a J shaped rod.
The short end of the J reached around under the inlet check valve ball.
Pulling up on the rod lifted and unseated the ball.

Yes ,the blade lifts on the return stroke ......I have a Racine Oilcut which had power downfeed too,all it does is strips and breaks blades.Anyhoo,a bandsaw is 10 times better,on blade usage,accuracy,and speed........But I remember as an apprentice,we used to stand round the power hacksaw as it chugged away and shoot the breeze.........the foreman would give us a rev...and we d say "But ,its sooooo slow"

john.k said:

Yes ,the blade lifts on the return stroke ......I have a Racine Oilcut which had power downfeed too,all it does is strips and breaks blades.Anyhoo,a bandsaw is 10 times better,on blade usage,accuracy,and speed........But I remember as an apprentice,we used to stand round the power hacksaw as it chugged away and shoot the breeze.........the foreman would give us a rev...and we d say "But ,its sooooo slow"

Click to expand...

I found for normal small jobbing shop work a good little metal "chop saw" style machine was the answer. After I did my back lifting the bloody arm the powers that be got me a chop saw, it was brilliant. Of course if you're working in a serious production environment a decent band saw is just what the doctor ordered.

One place I worked at had a German " Kasto " bandsaw. Now that was a production saw. It had all the bells and whistles, you just set it up and left it.

Regards Tyrone.

A little while ago,I got a Parkanson hydraulic lift and feed 12x12 bandsaw for very little...beautiful machine.......the owners says.....the guys cant use it ,because its got no digtal readout or computer.......Unbelieveable...who says millenials are useless.

John/Tyrone, thanks - apols for late reply - for some reason I don't seem to get emails from this forum. I'll check settings somewhere.

I did finally get it working. I made a 'cap' for the brass 'valve' thing above. It is not well made as it was an experiment, but it worked so well it is staying exactly as is.



With a ball bearing inside the valve and this guy afixed to its top - with the slots facing downwards into the valve - it all works as I'd hoped for. On ISO 68 Hydraulic oil.

Thanks for the help and advice.

Greg.