My Hydraulic Feed

[JimDawson]

Closed system? How do you deal with the changing fluid level requirement as the rod extends and retracts?

Bob, I did the same system to mine. What I did was to just leave a little air space in the system to handle the difference, has about 1/2 inch of free fall at the cutting area before the hydraulic fluid takes over. I'm using power steering fluid, that's what I had on the shelf at the time. It works just fine. 2.5 inch air cylinder I picked up in some scrap.

 

[Bob Korves]

I filled the system completely. when the fluid is pushed from the front it goes into the back and vise versa. Been working fine for a year now.

The rod side holds less volume for the same stroke because the rod displaces some fluid, so there has to be some air in a closed system for it to work. That is doable, just wondered which way you went. Adding a reservoir is another possibility but adds more complexity and cost to the trade offs. Air in the working side of the system adds bounciness, which is what the problem is with the OEM spring system. You want the saw frame to be rigid as it descends.

 

[Billh50]

Bob.....the volume on either side has no effect on feed. The restriction of the transfer of oil from rod side to back side is what controls the feed. It works for me just fine with no reservoir and has for over a year now. There is actually some air. But very little. The cylinder and lines were full but the control valve was not. So there is only what air was in the valve and fittings. Evidently that is enough air to solve any problems because I get no bounciness as you call it. I get a slow steady feed. The blade last longer and I get better cuts than I did before with the spring. The spring they use is evidently not a constant rate spring either.

 

[kingmt01]

Just found it. Thanks for taking the time to post it. I never even considered this upgrade until you mentioned it.

 

[Civilian_Again]

Bob...I used an air cylinder. A Bimba I bought on ebay for $8. The entire conversion cost me less than $20

Can you provide specs on the cylinder please? length? throw? bore? I'm trying to source parts for the mod and with this being my first endeavor into hydraulics, I'll take as much information as I can get. Also, in your initial post you mentioned using, "1/4" od clear tubing", was that rated air line? Since the valve you posted had 1/8th connections, I'm guessing the tubing was 1/4" OD 1/8" ID ?

 

[Billh50]

Ok.....the cylinder I used was about 1' OD with a 6" stroke. Because it was the cheapest one I found on Ebay that size. The hose was some 1/4" clear air hose that I had left over from work. The valve was an ebay purchase also.
I filled the front of cylinder with oil while the rod was fully retracted. I then installed the fittings and hose and filled those using an tiny funnel I had. Then installed the valve. By filling the front of the cylinder while rod was retracted it eliminated almost all of the bounce but also allowed the saw some bounce in case the blade was not perfect at the weld.

The 6" stroke can be less as I think the saw only uses about 3" of the stroke. It is easy enough to check what you need by measuring how much your spring stretches from when saw is full up to full down. I used the 6" because it was cheap. The whole setup only cost me less than $20 and was well worth it as my blades last much longer and saw cuts straighter.