Another Firewood Processor

[Wild Bill the 2nd]

It cuts OK for what we're doing.
So on the 22HP engine We have a 1.35ci pump running at 3000 rpm yielding 17.4 GPM to the saw.
The relief on our motor valve was set to 1500 psi from the factory. That is where we left it for more than 25 full cord. It worked alright but the saw would stall at 1500 PSI and run over the relief.

I ended up tweaking the relief up to 1800 PSI. Anything higher and we would stall out the 22HP engine when the chain bogged down. So it obviously cuts better with the extra pressure but we can still stall out the saw if we go through stuff too fast.

Bigger stuff we need to cut slower, I wish we had a bit more video to show but being as how we got this thing running so late in the season we were all focused on getting our firewood done.

In the end we have not maxed out the saw motor, we are limited by the gasoline engine.

 

[muddstopper]

If I am figureing this right, you are putting 17.4gpm to a .58 cuin motor, so it should be turning at 6930rpms. I believe you said you had a 15tooth .404 sprocket. Those speeds should have your chain running at 116ftsec. Thats pretty fast chain speed. Should cut like a scalded dog if you had the power to pull it. You need to increase the torque, which would mean increasing the pressure. If gas motor wont pull it, not much you can do. You are also already overspeeding the motor and getting close to max pressure rating, I dont know much more power you will be able to get out of that motor before it breaks. I would think that increaseing speed by 38% would also mean a reduction in safe pressures by a similar amount. Meaning your motor turning at 6930 rpms is only good to around 1500psi. Not sure if the pressure and flow rates would be linear but there is a relationship to be considered.

flow and pressure relationship I found for one type of motor.

MAX TORQUE & SPEED AT:
4650 PSI
1272 in-lbs Torque
1400 RPM
12 GPM


3000 PSI
840 in-lbs Torque
2200 RPM
18 GPM


2000 PSI
552 in-lbs Torque
3500 RPM
29 GPM


This is the same problem I saw with some of the factory processors I demo'ed. In small wood, they cut pretty good, but once wood dia starts getting bigger, saws started bogging down. It is also the reason I chose to go with a little bigger motor, so I could get the torque at lower pressure. In my situation, engine hp isnt going to be my limiting factor. My motor also has a higher pressure rating so I can turn the pressure up to 3000psi If i need to. I think, and its just my opinion, that a lot of the manufacturers use too small a saw motor. I know using a bigger motor requires all kinds of additional cost. More hp, bigger pumps, the whole nine yards ,= more cost to produce and a higher selling point. I guess this is the reason I decided to just build instead of buy.

 

[Wild Bill the 2nd]

Your numbers are correct except we ended up needing to go with a 16 tooth sprocket.
17.4 GPM into a .58ci motor yields 6930 rpm
At this speed the motor should be producing 154 in/lb of torque
6930 rpm running a 16 tooth sprocket and .404" chain yields 124 ft/sec chain speed.

I knew I was running the motor over the rated RPM but forgot to think that the max pressure would be downrated. The gear motors are fairly inexpensive so we will see how long it lasts for us.

For our next motor I would probably change to a .7ci model. It would run at 5742 rpm and develop 200 in/lb of torque.
At 5742 rpm the chain speed would still be 103 ft/sec. Probably a better setup with the current engine limitations.

Sounds like you have one heck of a machine planned. I can't wait to see it built!

 

[jonix]

WildBill, think the problem is your torque..but you have some kick *** chain speed!!!

I say this because I am working with almost 300 lb in @3300PSI, and once in a while the chain stalls..mostly in knots and more compact wood..

I work with 150 lb/in for about a month, and have to change it..the saw as to have a slow descend to cut..

But it all depends on type of chain and type of wood of course..

What kind of chain are you using?

 

[muddstopper]

Wild bill, you know the recommended speed for the .404 chain is 133 ftsec so you are pretty close with your setup, just need more power. I would run it till it blows and then think about what motor you want to replace it with. Might run for years, might blowup next cut, never know. If your prepared for the consequences, I would turn the pressure up and go for it.

Jonix, this is the saw motor Wildbill listed in his thread that he is using. 0.58 cu in MGG20025-BA1B3 HYD MOTOR SIDE PORTS. As you can see, its much cheaper than your F11 saw motor. Not saying it is better or worse than your saw motor. It is what it is.

 

[jonix]

Yes, it is much cheaper..

But it is running over limit RPMs, and at 2000 PSI is not going to have the torque needed..

think you are right..big displacement motors to run the saw, High torque at low pressure..and you only need to give it some decent oil flow to do the math..

 

[muddstopper]

Yes, it is much cheaper..

But it is running over limit RPMs, and at 2000 PSI is not going to have the torque needed..

think you are right..big displacement motors to run the saw, High torque at low pressure..and you only need to give it some decent oil flow to do the math..

I think you and WildBill have a similar problem, not enough hp to make the machine efficient. Dont know that my machine will be any better, and I am trying to do things with my machine you dont normally see on hobbiest or even most professional machines. I dont have much hair now, by the time I get mine built, My head will look like a peeled onion.

 

[farm boy00]

I think you and WildBill have a similar problem, not enough hp to make the machine efficient. Dont know that my machine will be any better, and I am trying to do things with my machine you dont normally see on hobbiest or even most professional machines. I dont have much hair now, by the time I get mine built, My head will look like a peeled onion.

Just remember to rub moisturizer and antibiotic ointment on it morning and night

 

[muddstopper]

I can always buy the spray on hair, with todays hair styles, I should fit right in:shocked:

 

[Wild Bill the 2nd]

Looks like muddstopper answered most all of Jonix's questions while I was away.
All but the chain, we are running Oregon 18HX chain.

We're not going out of our way to replace the saw motor now. Like you say we will wait until we blow out the seals and then we will see which way we want to go. Unless we change our engine setup I imagine that we will trade some chain speed for a bit more torque. I did find a 49hp Isuzu diesel for $1500. That didn't sound too bad...