Saw Dyno

[srcarr52]

Frequency filtering is not my area of expertise. Any chance you could help me out there?

I think though we can wait and see if mechanical improvements help out first -- would really cool if we didn't need to filter and just bin the datapoints collected into various RPM ranges and plot from low to high w/ points that fit in each range averaged. A plot of resulting points may end up looking really nice. I can make the software do it automatically (like folks have done manually by reading a scale at various RPMS dialed in with the value) and make the range of each bin adjustable -- to try 50, 100, 200, 250 rpm ranges. I've got plenty of resolution on both RPM and load cell to do this. I'm going to also make the RPM display interval independent of RPM collection interval -- the display updating every 10th second is good but I can collect RPMs more often then that now that I have more pulses per rev and no reduction ratio robbing of resolution.

Also Shaun I'm very happy that the 16 pulses per rev on the hardware encoder interface on the beaglebone computer keeps up no problem w/ shaft spinning at saw RPM rate. My RC filter for noise is good through ~15000 hz frequency so no problem there.

You could do a low pass filter (RC filter) on the the load cell as well before or after the amplifier, it would need to be around 100Hz or so.

 

[malk315]

Thanks Shaun. I'll have the hardware guys from my work help me w/ adding that based on the schematic for the small adafruit board I'm using. We're going to do a cape board for the beaglebone and we can add the RC filter as I'll be able to ditch the adafruit board after using it's schematic as a base.

 

[wcorey]

On the max RPM limitation, I have tried it with a short direct return loop with 1/2" line/no valve and there was no difference.
I'm thinking it's just frictional resistance from the drive train and pump.

The cooler is there in the attempt to avoid a large reservoir. When I was trying extended runs I put it in a bucket of water, for the short runs we were doing at Eric's the temps stayed pretty low and the water cooling wasn't required.

If this was having cavitation issues, wouldn't we be seeing random swings in RPM under load?

 

[srcarr52]

On the max RPM limitation, I have tried it with a short direct return loop with 1/2" line/no valve and there was no difference.
I'm thinking it's just frictional resistance from the drive train and pump.

The cooler is there in the attempt to avoid a large reservoir. When I was trying extended runs I put it in a bucket of water, for the short runs we were doing at Eric's the temps stayed pretty low and the water cooling wasn't required.

If this was having cavitation issues, wouldn't we be seeing random swings in RPM under load?

Open the reservoir, is there bubbles?

 

[malk315]

Shaun I'm going to add an RC filter for 100 Hz before the amp (amp is inside the IC on the small proto board currently in use) so next time I test with Bill I can see how well it filters any noise.
I'll set it up so I can add the filter and remove it so I can compare how it does.

Pretty psyched with the improvements so far. Restores motivation to keep working on it / making it better.

I'm going to try and build another set of electronics and in the process make it easier to replicate on the setup Bill has and donate a set to @Dieselshawn he's got a hydraulic dyno w/ manual scale and tach.

 

[srcarr52]

Shaun I'm going to add an RC filter for 100 Hz before the amp (amp is inside the IC on the small proto board currently in use) so next time I test with Bill I can see how well it filters any noise.
I'll set it up so I can add the filter and remove it so I can compare how it does.

Pretty psyched with the improvements so far. Restores motivation to keep working on it / making it better.

I'm going to try and build another set of electronics and in the process make it easier to replicate on the setup Bill has and donate a set to @Dieselshawn he's got a hydraulic dyno w/ manual scale and tach.

I'd make the prototype filter on a socket so you can swap the resistor and cap for different frequency, 100Hz, 200Hz, ect.

I could use a set of electronics and software if I ever get around to making the chainsaw adapter for my kart dyno.

 

[malk315]

I'd make the prototype filter on a socket so you can swap the resistor and cap for different frequency, 100Hz, 200Hz, ect.

I could use a set of electronics and software if I ever get around to making the chainsaw adapter for my kart dyno.

Exactly what I plan.

Be happy to make more electronics once finished and smaller with cape board and LEDs optional.


Sent from my XT1585 using Tapatalk

 

[wcorey]

Open the reservoir, is there bubbles?

Of course there's bubbles, just like you'd see in the p/s res on a car when you work the steering.
My biggest concern with cavitation was if it compromised the ability of the pump to slow the saw down, so far that hasn't been an issue.
Next concern is if it affects the data stream, though my gut feeling wants me to think that's more about the mechanical noise of the drivetrain. As with the m'cycle brake setup, to me the jitter just looks mechanical in nature. Not much more than a guess though...

It will be very interesting to see how the electronics behave on DieselShawn's setup, more of a direct line on the drivetrain and the pump is damped through a coupling.

I still need to find a hydraulic gear pump of the right capacity that's rated for side load, unidirectional would be nice too.
I can hang it off the old setup in place of the disc brake, might eliminate a few variables.

 

[X 66 stang347 X]

What about a small log splitter pump with a lovejoy coupler?

 

[wcorey]

What about a small log splitter pump with a lovejoy coupler?

That's more or less what Dieselshawn has going on...