Dyno

[Red97]

Nice!

Most I have seen are 4.5-5 ftlb on ported 372. At around 7k rpm

 

[Ronie]

Nice!

Most I have seen are 4.5-5 ftlb on ported 372. At around 7k rpm

Something must not be right then. I'll remeasure the arm, should be 1' from the center of the pump shaft and I'm going to order another scale that has the numbers that light up.

 

[Ronie]

Nice!

Most I have seen are 4.5-5 ftlb on ported 372. At around 7k rpm

Looks like my scale will be ok, if the camera is level or below the display the numbers become clearer so when I mount it I'll raise it up some. I also tested some weights against another scale I have and it's accurate. My arm is around 1/16"-1/8" off but there is enough play in the pump mount to correct that. Maybe it didn't read 9lbs, it was hard to see the numbers.

Above level




Level

 

[Red97]

Your overall ratio will play into it.

Saw is spinning 10k pump is spinning ? 5k? So that would be accurate

4.5 ftlb at the saw 2:1 ratio double the tq half the rpm.

 

[wcorey]

Yeah 9flbs is a just bit high, lol, saw would be putting out 12hp or something.
As Red just stated it's likely to do with how you're calculating in the ratios.

The valve looks sort of stiff to turn, you might try loosening the gland nut until it almost leaks...

 

[Red97]

Nothing wrong with the numbers not matching either. As long as every time you test that saw it reads the same 9ftlb each time.

 

[Ronie]

Your overall ratio will play into it.

Saw is spinning 10k pump is spinning ? 5k? So that would be accurate

4.5 ftlb at the saw 2:1 ratio double the tq half the rpm.

I think I understand, I was thinking that a 1' arm would equal 1ftlb torque. my gear ratio is .28 so I'll have to figure out a formula to convert it to real torque numbers. I tried it again and and it got up to 13lbs on the scale.

@wcorey I loosened it a little before the video but your right, it's still to tight.

3rd run, no tach yet.

 

[Ronie]

If My ratio is 1 to .28 would I figure the torque like this, .28 times the reading on the scale to get the torque reading?

 

[Mycamaro_68]

.28:1 ratio is actually overdrive. I'm guessing you figured your ratio backwards. It should be driven teeth number divided by drive teeth number. Hopefully that makes sense.

 

[Ronie]

.28:1 ratio is actually overdrive. I'm guessing you figured your ratio backwards. It should be driven teeth number divided by drive teeth number. Hopefully that makes sense.

your right, it's 1 to .28.

 

[srcarr52]

Your 7:10, 11:35 gear set you had shown before is (7/10)*(11/35)=0.22. So for every 1 rev of the crank the pump turns 0.22 turns. Thus your output torque on the pump is 1/0.22=4.5454.

So the torque at the crank is your scale torque *0.22.

13*.22 = 2.86 ft*lbs.

 

[Ronie]

Your 7:10, 11:35 gear set you had shown before is (7/10)*(11/35)=0.22. So for every 1 rev of the crank the pump turns 0.22 turns. Thus your output torque on the pump is 1/0.22=4.5454.

So the torque at the crank is your scale torque *0.22.

13*.22 = 2.86 ft*lbs.

Thanks, now I'm using 7 to 10, 24 on the same shaft as the 10 to 60.

 

[Mycamaro_68]

Thanks, now I'm using 7 to 10, 24 on the same shaft as the 10 to 60.

View attachment 344638 View attachment 344639

So 7 tooth on saw and 10 tooth on jackshaft, right? That would be 10 divided by 7 which is 1.43 to 1. So 10,000 rpm saw speed would mean the jack shaft is spinning 6,993 rpm.

Then from the jack shaft to the pump you have 24 tooth on jack shaft and 60 tooth on pump shaft, right? That would be 60 divided by 24 which is 2.5 to 1. Which would make the pump shaft speed 2,797 rpm.

So for a final drive number you are going from 10,000 rpm to 2,797 rpm. 10,000 divided by 2,797 is 3.58 to 1 ratio. Which I believe would mean that your 13 ft lbs divided by 3.58 would equate to 3.63 ft lbs.

Do my mathmaticals look right to you Shaun? @srcarr52

 

[Ronie]

So 7 tooth on saw and 10 tooth on jackshaft, right? That would be 10 divided by 7 which is 1.43 to 1. So 10,000 rpm saw speed would mean the jack shaft is spinning 6,993 rpm.

Then from the jack shaft to the pump you have 24 tooth on jack shaft and 60 tooth on pump shaft, right? That would be 60 divided by 24 which is 2.5 to 1. Which would make the pump shaft speed 2,797 rpm.

So for a final drive number you are going from 10,000 rpm to 2,797 rpm. 10,000 divided by 2,797 is 3.58 to 1 ratio. Which I believe would mean that your 13 ft lbs divided by 3.58 would equate to 3.63 ft lbs.

Do my mathmaticals look right to you Shaun? @srcarr52

I got almost the same when I figured it out but used .28 and got 3.64ftlbs.

 

[srcarr52]

I got almost the same when I figured it out but used .28 and got 3.64ftlbs.

Yup!

 

[Ronie]

I don't think 3.64ftlds is the real torque because that saw has a lot more than a stock 372, maybe with the corrected torque it would be right.

 

[Ronie]

I ran out of fuel with the 372 so I tried out my 562 with a light port job, I'll mix up some fuel tomorrow and try the 372 with a tach.

562 at 9400 rpm, tach is not the one I plan on using. Hp seems low to me

 

[Ronie]

I must be figuring it wrong, I looked a @Red97 video of a stock and ported 562 and mine is well below the stock one and it runs a lot better than it did when it was stock.

 

[Ronie]

Here's a corrected HP/TQ run on my 562 and here's what I'm doing to get these numbers,

Scale pounds x .28 to get the uncorrected TQ
Uncorrected TQ x RPM / 5252 to get the uncorrected HP
Use a corrected HP calculator to get the corrected HP
Corrected HP x 7127 / RPM to get the corrected TQ

Any Ideas what the problem could be?

 

[Ronie]

Got my pump and saw tach display mounted in a case and powered by a 9v battery, should be easier to see on camera. My idler wheel didn't last long, soft rubber, so I ordered a sprocket to put on it and I also ordered a fluid filed pressure gauge, the one that's on it reads around 600psi before I even I start the saw. If I can't get my scale torque figured out I'll need a good gauge to get my HP numbers from.