muddstopper
Veteran Member
With nothing better to do, I decided to do a little math experimenting on what it would take to build a hyd saw with similar power and speed as the 372xp the OP says he wants to performance match. I am doing the math as I type, so it it looks jumbled, just overlook .
First I had to look up the saw spec. Fist thing was hp, the 372 specs are in Kw instead of hp, and a lot of other things where metric so it meant a lot of converions, so because of rounding my numbers wont be exact. The 372 is rated for 4.1kw/5.5hp.@10200rpms. Torque is 3.8Nm/2.8ftlbs. Chain is 3/8 pitch and runs at 22.7m/s or 74.5fts.
Next I had to find a motor that would come close to meeting those spec. Ironicly the motor I posted in my fist reply came pretty close to fitting the requirement..
.7 cu in PARKER MGG23-BA1A3 HYD MOTOR.
knowing I had to use a larger sprocket to get the proper chains speed, and the sprocket size had to be something easily found and compatable with a standard saw bar., I picked the 14 pin sprocket which is double the size of the standard 7pin sprocket on the 372. this meant I would have to find a motor that would turn 5000rpms if I was going to stay even close to the saw chain speed. The .7 gerotor motor will turn. 5000rpms. I then compared the torque numbers of the motor. Of course it was in inlbs and not ft lbs, 166in lbs is 13.8ftlbs. One has to factor the torque numbers are rated at the shaft and I am not sure how to convert the actual torque numbers with doubleing sprocket size but I am guessing the number would be at least cut in half. Lets just call it 6.9ftlb torque, at 5000rpms.
Next I needed to figure the amount of oil to reach 5000rpms and the pressure required to produce the torque. On the website the motor is listed as 5000@rpms with 15gpm @ 1500psi. Online calculators suggest that it takes 14.6hp to produce the oil flow and pressure needed to run the motor at max power. A little more calculations suggest that a .7cuin motor at 5000rpms and 13.8lbs torq would produce 13.1hp. All these numbers are a lot more than the 372 gas saw. so it looks good so far.
Chain speed is the next thing to consider. "
Take the chain pitch and multiply by 2. Multiply the above number by the number of teeth of the saw sprocket.
Multiply that number by the saw R.P.M.
The final answer will be the chain speed in inches per minute, just divide by 12 to convert to feet per minute."
So ,(3/8x2x14x5000rpm)/12= 4375ftpermin. to convert to fts divde by 60sec=72.9fts. Pretty darn close to the 372 @ 74.47fts.
The one thing to consider is that even tho this hyd saw has a little less chain speed than the gas powered 372, the extra torque and hp should make for a comparable cut speed. Also consider that all hyd math was being done with advertised numbers, nothing has been factored into actual efficiency numbers, typical at 80%. efficiency. So while the numbers may be close, actual performance might not measure up. My saw motor is almost twice as big and will handle 3 times the hyd pressure and used a larger pitch chain. I am also using a 7.3 diesel engine to pull all the pumps. If you want big and fast, you have to go up in power, but the .7cuin motor along with his 17hp engine is pretty close to matching his 372 saw performance, which is what he is looking for. He wont have any oil flow left over for other processor functions and his operation will more than likely be a one function at a time processor,
First I had to look up the saw spec. Fist thing was hp, the 372 specs are in Kw instead of hp, and a lot of other things where metric so it meant a lot of converions, so because of rounding my numbers wont be exact. The 372 is rated for 4.1kw/5.5hp.@10200rpms. Torque is 3.8Nm/2.8ftlbs. Chain is 3/8 pitch and runs at 22.7m/s or 74.5fts.
Next I had to find a motor that would come close to meeting those spec. Ironicly the motor I posted in my fist reply came pretty close to fitting the requirement..
.7 cu in PARKER MGG23-BA1A3 HYD MOTOR.
knowing I had to use a larger sprocket to get the proper chains speed, and the sprocket size had to be something easily found and compatable with a standard saw bar., I picked the 14 pin sprocket which is double the size of the standard 7pin sprocket on the 372. this meant I would have to find a motor that would turn 5000rpms if I was going to stay even close to the saw chain speed. The .7 gerotor motor will turn. 5000rpms. I then compared the torque numbers of the motor. Of course it was in inlbs and not ft lbs, 166in lbs is 13.8ftlbs. One has to factor the torque numbers are rated at the shaft and I am not sure how to convert the actual torque numbers with doubleing sprocket size but I am guessing the number would be at least cut in half. Lets just call it 6.9ftlb torque, at 5000rpms.
Next I needed to figure the amount of oil to reach 5000rpms and the pressure required to produce the torque. On the website the motor is listed as 5000@rpms with 15gpm @ 1500psi. Online calculators suggest that it takes 14.6hp to produce the oil flow and pressure needed to run the motor at max power. A little more calculations suggest that a .7cuin motor at 5000rpms and 13.8lbs torq would produce 13.1hp. All these numbers are a lot more than the 372 gas saw. so it looks good so far.
Chain speed is the next thing to consider. "
Take the chain pitch and multiply by 2. Multiply the above number by the number of teeth of the saw sprocket.
Multiply that number by the saw R.P.M.
The final answer will be the chain speed in inches per minute, just divide by 12 to convert to feet per minute."
So ,(3/8x2x14x5000rpm)/12= 4375ftpermin. to convert to fts divde by 60sec=72.9fts. Pretty darn close to the 372 @ 74.47fts.
The one thing to consider is that even tho this hyd saw has a little less chain speed than the gas powered 372, the extra torque and hp should make for a comparable cut speed. Also consider that all hyd math was being done with advertised numbers, nothing has been factored into actual efficiency numbers, typical at 80%. efficiency. So while the numbers may be close, actual performance might not measure up. My saw motor is almost twice as big and will handle 3 times the hyd pressure and used a larger pitch chain. I am also using a 7.3 diesel engine to pull all the pumps. If you want big and fast, you have to go up in power, but the .7cuin motor along with his 17hp engine is pretty close to matching his 372 saw performance, which is what he is looking for. He wont have any oil flow left over for other processor functions and his operation will more than likely be a one function at a time processor,
