Thanks for showing us your homemade dyno :) Don't know if i'll ever make one, but its on my list for when I have the time and capability. I just got into modding my saws. Only done basic muffler mod with port matching, and some light work on the exhaust port, mainly opening it up slightly towards the exit and jus a touch at the inlet. Put an extra quarter inch hole in the muffler, kept the spark arrestor in. Plus a slight timing advance. Opened the airbox slightly. Using my echo 355t as practice. Definitely stronger, and definitely has a little stumble in the mid range, both going up and when coming down. Feels like its lean in the mid, and been trying to figure out how to get more fuel to the mid range. A porting video I saw mentioned lowering the intake richens things up, so I'll try that, and hopefully get a nice mid, and simply have to turn my idle and high end in a touch. Just sharing with you, one tinkerer to another.
Forgive me for commenting twice but id like to add....i really enjoy your channel ive learned alot from you ....i restore old logging aws and really want my own dyno
That is pretty near the exact rig that I've dreamed up to play with. The only thing that I'd consider doing is actually gearing down the disk speed. Bike disks aren't designed to be spun up to 12000rpm. You really don't want a 140mm stainless steel disk going projectile on you.
Love the dyno; have two suggestions/thoughts for you to consider. 1) For the HP calc, you need to have the RPM of the driven end, and not the saw. Consider that, if you were to put a driven sprocket with 2x more teeth (to gear it down) it would show 2x ft. lbs.. but it would be 1/2 speed which would give same HP. The saw will show more HP than it is actually putting out due to the RPM reading being on engine instead of driven shaft... in other words, the torque and speed need to be on the same shaft. 2) the distance from the torque arm to the scale needs to be measured from the pivot to the point on the scale (which is actually more than 1ft I assume; I understood your top arm to be 1 ft) since the "L" shaped torque arm is rigid will read just as if the torque arm was straight from the pivot to the scale impact point. So, I believe you are showing a falsely high HP due to using engine speed vs shaft speed WHILE you are showing a falsely low HP due to using a longer (than calculated) torque arm. Each can be corrected in the math and the dyno need not be modified. Maybe you've already considered each point; I know it's impossible to convey everything in one short video. Thanks for sharing; I enjoyed the video.
Thanks for the comment, yes they are the same so long as the clutch is fully engaged, but I'm upgrading to one on the driven shaft and one on the dyno, I did have a dyno problem, the drive star at the chain has failed after putting one of my more powerful saws on so I've got my work cut out making a new drive sprocket gear at the moment, but thanks for your interest.
@@marklutwyche8578 Thank you. I had wrongfully assumed that the star sprocket was not a 7 tooth, too; I had assumed there was a reduction and, even with no clutch slippage, the brake was turning slower than the engine. Thanks for the response.
Yes I've taken all into account, am fitting an rpm meter to the disc spindle to see if there is a difference but I doubt it as I'm measuring at the chain basically like a car is measured at the wheel, to me hp at the chain is what I want though it will be more at the crank, but I really want to read hp at the chain as that's what counts, I can also re adjust my arm to set the dyno to my standard saw hp as a set point then I can do mods and measure the difference.
@@marklutwyche8578 I whole-heartedly agree with everything you said as making it same as a wheel dyno on a car; more realistic than "engine hp". Thanks; know you can't cover e'thing in a short vid, but thought it was worth mentioning.
I appreciate it ....I am thinking I may build one ....I have looked at several on you tube but to me I think yours may be the best version to build...... hydraulic pumps heat the oil up so to me yours looks like it may work the best ....what did you use to drive the rotor? Is it a regular nose sprocket?
Fascinating and well done video. What you achieved mechanically at minimal expenditure is remarkable. Bravo.
Glad you enjoyed it!
Thanks for showing us your homemade dyno :) Don't know if i'll ever make one, but its on my list for when I have the time and capability.
I just got into modding my saws. Only done basic muffler mod with port matching, and some light work on the exhaust port, mainly opening it up slightly towards the exit and jus a touch at the inlet. Put an extra quarter inch hole in the muffler, kept the spark arrestor in. Plus a slight timing advance. Opened the airbox slightly. Using my echo 355t as practice.
Definitely stronger, and definitely has a little stumble in the mid range, both going up and when coming down. Feels like its lean in the mid, and been trying to figure out how to get more fuel to the mid range. A porting video I saw mentioned lowering the intake richens things up, so I'll try that, and hopefully get a nice mid, and simply have to turn my idle and high end in a touch.
Just sharing with you, one tinkerer to another.
Forgive me for commenting twice but id like to add....i really enjoy your channel ive learned alot from you ....i restore old logging aws and really want my own dyno
You can message me as many times as you like, I'm sorry but I have phases of replying as I work full time, thank you for the kind comment.
That is pretty near the exact rig that I've dreamed up to play with. The only thing that I'd consider doing is actually gearing down the disk speed. Bike disks aren't designed to be spun up to 12000rpm. You really don't want a 140mm stainless steel disk going projectile on you.
Love the dyno; have two suggestions/thoughts for you to consider. 1) For the HP calc, you need to have the RPM of the driven end, and not the saw. Consider that, if you were to put a driven sprocket with 2x more teeth (to gear it down) it would show 2x ft. lbs.. but it would be 1/2 speed which would give same HP. The saw will show more HP than it is actually putting out due to the RPM reading being on engine instead of driven shaft... in other words, the torque and speed need to be on the same shaft. 2) the distance from the torque arm to the scale needs to be measured from the pivot to the point on the scale (which is actually more than 1ft I assume; I understood your top arm to be 1 ft) since the "L" shaped torque arm is rigid will read just as if the torque arm was straight from the pivot to the scale impact point. So, I believe you are showing a falsely high HP due to using engine speed vs shaft speed WHILE you are showing a falsely low HP due to using a longer (than calculated) torque arm. Each can be corrected in the math and the dyno need not be modified. Maybe you've already considered each point; I know it's impossible to convey everything in one short video. Thanks for sharing; I enjoyed the video.
Thanks for the comment, yes they are the same so long as the clutch is fully engaged, but I'm upgrading to one on the driven shaft and one on the dyno, I did have a dyno problem, the drive star at the chain has failed after putting one of my more powerful saws on so I've got my work cut out making a new drive sprocket gear at the moment, but thanks for your interest.
@@marklutwyche8578 Thank you. I had wrongfully assumed that the star sprocket was not a 7 tooth, too; I had assumed there was a reduction and, even with no clutch slippage, the brake was turning slower than the engine. Thanks for the response.
Yes I've taken all into account, am fitting an rpm meter to the disc spindle to see if there is a difference but I doubt it as I'm measuring at the chain basically like a car is measured at the wheel, to me hp at the chain is what I want though it will be more at the crank, but I really want to read hp at the chain as that's what counts, I can also re adjust my arm to set the dyno to my standard saw hp as a set point then I can do mods and measure the difference.
@@marklutwyche8578 I whole-heartedly agree with everything you said as making it same as a wheel dyno on a car; more realistic than "engine hp". Thanks; know you can't cover e'thing in a short vid, but thought it was worth mentioning.
Do you know what i would need to make a small engine dyno print out a graph on a computer screen?
I use live data rev counters and a cheap waking scale that can measure in lbs, nothing special really.
I use a cheap way scale that measures lb and cheap rev counters from e,bay amazon.
I appreciate it ....I am thinking I may build one ....I have looked at several on you tube but to me I think yours may be the best version to build...... hydraulic pumps heat the oil up so to me yours looks like it may work the best ....what did you use to drive the rotor? Is it a regular nose sprocket?
Yes I split a guide bar and used all the parts to make a drive system.
The brake disc does heat up massively but it holds out through short tests. And above all it was cheap but good fun.