Chainsaw dynometer build.

[dynodave]

Hydraulic brake dyno

1. If you have a hydraulic pump big enough ...
2. Pump sprocket big enough to reduce pump RPM to prevent cavitation...
3 High resolution Pressure gauge before outlet variable restrictor that you mentioned ,
and you track engine RPM you should be fairly good to go.
That is what I have on my 100HP motorcycle chassis brake dyno.

The pressure guage effectively IS your load cell/torque arm.

You will need a pretty big tank of oil or it will get hot enough to fry fish unless you build in a water intercooler. Viscosity change of the oil due to heating will make calibration and consistant reading very difficult.
Also IMO a hydraulic dyno is good for a load cell , it will be useful for relative readings, but "calibration" will be more problematic due to high internal losses at low engine power levels.
I plan to build a smaller engine dyno approx 30 HP with a few bar mount adaptors for my chainsaws.:msp_rolleyes:
good luck

 

[chadihman]

The easiest way around the clutch is to use the fly wheel. If properly mounted it could handle a load strong enough to bring the engine down.

Good idea but I'm almost positive a good shape clutch will hold tight. Think about this way. Your saw is way below 9000 rpms when your chain stops when your using your spikes and pulling on the saw to stall the chain. Husky site says most of there saws have max engine power at 9000-9600 rpms. The clutch should never slip at that rpm.

 

[chadihman]

What about something like a small disk brake? The caliper could be mounted on the lever and the saw could turn the brake rotor.

Just trying to think cheap, yet effective.

-phillip

To much heat! A hyd pump is needed to be able to have long run times. At work we have a large dyno for tractors. It is a brake style. It needs a garden hose hooked to it to keep it cool.

 

[Dan_IN_MN]

I know a guy that used to have an Outdoor power equipment store. He still has his chainsaw dyno which I don't believe he uses any more. :msp_ohmy:

 

[LowVolt]

Eddy-Current and Powder Dynamometer Applications


-phillip

I wonder how much it is....

 

[moody]

Good idea but I'm almost positive a good shape clutch will hold tight. Think about this way. Your saw is way below 9000 rpms when your chain stops when your using your spikes and pulling on the saw to stall the chain. Husky site says most of there saws have max engine power at 9000-9600 rpms. The clutch should never slip at that rpm.

No but the clutch side would ad a variable. The flywheel would be a more truthful reading because its directly driven from the crank. The clutch side loses power through more moving parts.

 

[chadihman]

No but the clutch side would ad a variable. The flywheel would be a more truthful reading because its directly driven from the crank. The clutch side loses power through more moving parts.

The clutch is solid to the crank when its locked up. I would connect to the flywheel but how the heck would I start the saw? I'm going to use a chainsaw bar with the spocket end chopped off. I'll then have a large sprocket on the end of the bar. The large sprocket would be connected to a shaft on bearings with a coupler atached to the pump. I'm still researching a high rpm pump as I dont want to many reductions.

 

[chadihman]

I know a guy that used to have an Outdoor power equipment store. He still has his chainsaw dyno which I don't believe he uses any more. :msp_ohmy:

I'd like to know a little more about that. Maybe a couple pics or a phone #

 

[spindrift7mm]

Could be simple

Chadihman, here's a thought. Flywheel directly attached to chain via double end bar,maybe 40-50 lbs automotive for larger saws and lighter for smaller saws. In simple form run the saw in stock form, timed to say 10,000. Then mod the muffler or port and run again compare gains. I believe TW posted that there were several software programs that would run with with this type set up. I think I would drive the flywheel with a rim drive so rims could be changed to match saw pitch and replaced for wear which I suspect to be high. Good Luck Ken

 

[2dumb4words]

No but the clutch side would ad a variable. The flywheel would be a more truthful reading because its directly driven from the crank. The clutch side loses power through more moving parts.

I can't see where taking power off the clutch side would be a problem. Where do you plan to run that power when cutting? That's what clutches do.

And subscribed.

 

[Mastermind]

Watching......

A flywheel dyno would be the simplest.

 

[chadihman]

Watching......

A flywheel dyno would be the simplest.

I agree a flywheel setup would be the simplest but what fun is spooling it up and stopping. I want to be able to pull the saw down to 8000-10000 rpms and hold it. What a great way to break in saws. I could easily pull the saw down to any rpm with the simple adjustment of a needle valve. I dont mean to boast but this is my kind of thing. I love designing and building things. A few years ago I designed and built power unit for our shop at work. It has a 10 hp electric motor driving two pumps. We use it to run farm equipment in the shop. It runs a pto shaft at any variable rpm and supplys hyd pressure for opperating cylinders. It rolls around on wheels and has no smell exhuast or noise. They want me to build another one.

I will build this don't worry. I already started ordering some parts. Flea bay is my friend. Please be patient with me as I'm still recovering from sugery. I will start a new thread when I'm finished.

 

[moody]

The clutch is solid to the crank when its locked up. I would connect to the flywheel but how the heck would I start the saw? I'm going to use a chainsaw bar with the spocket end chopped off. I'll then have a large sprocket on the end of the bar. The large sprocket would be connected to a shaft on bearings with a coupler atached to the pump. I'm still researching a high rpm pump as I dont want to many reductions.

spin the mount. Just like the spin start on the craftsman weed eaters. You can if you're careful can start a saw with a drill.

 

[moody]

Watching......

A flywheel dyno would be the simplest.

Nice to see someone agrees

 

[young]

bottom line, i want to know the horse power/torque to the wheels, not the crank, so to speak.

 

[LowVolt]

Watching......

A flywheel dyno would be the simplest.

Your videos speak for themselves but it would be very cool to see a stock curve next to a ported curve and some hard numbers to show what a performance work saw is capable of.

 

[gtsawyer]

One of my pet peeves is not being able to accurately compare power readings from saw/saw or from mod to mod.

Subscribed.

 

[one.man.band]

To much heat! A hyd pump is needed to be able to have long run times. At work we have a large dyno for tractors. It is a brake style. It needs a garden hose hooked to it to keep it cool.

about the heat..... 50cc saw puts out about 2 ft-lbs torque stock. how much heat would it make under load? who knows. you would barely get a ft-lb torque wrench to get a reading that small. a bicycle caliper rim brake that can stop a kid easily holds back quite a bit more than that under light pressure.

to me its getting soething that could hold together without killing yourself with metal shrapnel at 14000 rpm.

-omb

chadihman .......don't confuse anyone with dyno numbers

 

[one.man.band]

rep sent. be safe. and good luck with your build.

-omb

 

[chadihman]

about the heat..... 50cc saw puts out about 2 ft-lbs torque stock. how much heat would it make under load? who knows. you would barely get a ft-lb torque wrench to get a reading that small. a bicycle caliper rim brake that can stop a kid easily holds back quite a bit more than that under light pressure.

to me its getting soething that could hold together without killing yourself with metal shrapnel at 14000 rpm.

-omb

chadihman .......don't confuse anyone with dyno numbers

Darn it i had a plan. Now you got me thinking again. I found torque specs on huskys site. The big saws will probably have around six ft/lbs. A brake would handle that for a while. That sure would be easier and cheaper. I'm worried that a brake might be hard to get a stable rpm. I think a hyd pump with a needle valve would be much smoother Adjustment on loaded rpm would be gentle not jittery.