Another chainsaw dyno...

[Dieselshawn]

I’ll have to make a tripod or see if I can get one somewhere.

I need a tripod anyways as I like taking pictures and videos.

I did not expect my phone to have wavy motion videos.

 

[Dieselshawn]

Here’s my attempted video of the dyno in use.

 

[Nutball]

I want to see some cylinder temps during that torture test. Do you aid cooling in any way? I remember a Redbull661 test where the cylinder reached like 425-450F after about a minute.

 

[Dieselshawn]

I want to see some cylinder temps during that torture test. Do you aid cooling in any way? I remember a Redbull661 test where the cylinder reached like 425-450F after about a minute.

Nothing to help with cooling. Other than cleaning up the fins from fines and dirt over time.

I run them as is. If a saw cannot perform on its own, then they’re not much use as a logging saw. Especially a milling saw. I’m not even cutting wood that would make the bar and chain hot.

The guys doing milling are draining fuel tanks per slab.

These are full time logging saws.

If it’s a racing saw, then yes, I will add a cooling fan or run a much shorter load test that would concentrate more at the power band that’s needed.

 

[Nutball]

I've often wondered what the duty cycle of different saws is. There must be a limit if people are able to cook them on a mill, but then again they must survive a stump cut and repetitive long cuts through 30-40" of wood.

 

[Dieselshawn]

There is a recent video that I saw of several guys with saws taking about 10 hours over 2 days to cut down a fire damaged sequoia tree.

Tree was 14 feet across where they were cutting.

 

[huskihl]

There is a recent video that I saw of several guys with saws taking about 10 hours over 2 days to cut down a fire damaged sequoia tree.

Tree was 14 feet across where they were cutting.

From what I’ve seen, probably 3 hours of that was swinging an axe knocking out the face cut wedge

 

[MustangMike]

So what were the results? I can't read those gages in my video.

 

[Dieselshawn]

So what were the results? I can't read those gages in my video.

Here’s my number chart for the 660 Mastermind.



This is a stock 660 below.

 

[huskyboy]

Here’s my number chart for the 660 Mastermind.

View attachment 312217

This is a stock 660 below.

View attachment 312218

Nice little gains.

 

[Sawrain]

For those that have run chainsaw dyno’s, I was wondering if there is a difference/change in brake response for saws that have noticeably declining torque after peak torque, compared to saws that are fairy flat or keep gaining torque until clutch slip occurs.

I just attached a 100a automotive alternator to a saw, hoping it might be a viable dyno brake, no problems stopping a Dolmar 9010, but speed control is a little sensitive when passing peak torque, I’m unsure if this is alternator brake specific behaviour or something that other hand controlled brakes might suffer?

I don’t plan to use alternator output as a power measuring tool, but a stock 9010 peaked at 3kw, approx 77 Amps and 38 volts, a bit meaningless without a knowing system efficiency, but interesting none the less.

 

[Nutball]

speed control is a little sensitive when passing peak torque

Like how loading some saws in wood to a certain point makes them stall suddenly while others slowly come to a stop. When the saw passes peak torque the brake then requires more than the engine can provide causing the engine to slow and produce even less. It will eventually balance out as the reduced speed requires less torque to turn, and as the clutch starts slipping. Friction brakes would probably be more sensitive than a generator like what you used. It would help to test different ways of loading the engine and after finding what works best, calibrate its sensitivity to the engine power you are dealing with through gearing, governor, control curve, ect.

 

[Sawrain]

Like how loading some saws in wood to a certain point makes them stall suddenly while others slowly come to a stop. When the saw passes peak torque the brake then requires more than the engine can provide causing the engine to slow and produce even less. It will eventually balance out as the reduced speed requires less torque to turn, and as the clutch starts slipping. Friction brakes would probably be more sensitive than a generator like what you used. It would help to test different ways of loading the engine and after finding what works best, calibrate its sensitivity to the engine power you are dealing with through gearing or control curve, ect.

It is not unexpected behaviour, it’s not hard to explain.

I used to load and unload vintage stationary engines as a kid with a plank of wood on the pulley or flywheel, the game being how low can you take it without stalling.

But is it something those operating water brake, hydraulic brake and friction brake dyno devices all find obvious?

 

[Nutball]

I would be interested to hear how the hydraulic brake compares and what kind of a torque curve they have.

 

[Sawrain]

I would be interested to hear how the hydraulic brake compares and what kind of a torque curve they have.

At this stage I’m only using about a 1/4 turn of my power supply adjustment knob range from low to high load, so it’s definitely not as finely controlled by hand as a hydraulic needle valve controlled dyno.

@Dieselshawn @Red97 @malk315

Any input on your style dyno and how they react when passing peak torque? Or say 7 to 8k rpm on a modern saw?

I would guess similar happens, but am interested in how the different brakes are to operates.

 

[wcorey]

Are you running no load, peak rpm at wot and then loading it down?

 

[Sawrain]

Are you running no load, peak rpm at wot and then loading it down?

Yeah, unloaded, full speed then dragging it down.

It’s only roughly rigged up, just to see if it will even work, the other thing to get used to is the non linear response, not much braking occurs from feeding the alternator rotor coil 0-8 volts, then it really starts to load things between 8 and 10 volts.

The response doesn’t make it unusable, it was just notable.

 

[Dieselshawn]

On my machine, once the saw passes peak torque, the pressure gauge stops climbing.

As the rpms was being pulled down, the torque rises as the speed slows.

Eventually the pressure gauge stops climbing even while the rpms was still being pulled down.

In my video, the 660 has been pulled down as far as 6,960 rpms and the clutch is still holding.

 

[Red97]

At this stage I’m only using about a 1/4 turn of my power supply adjustment knob range from low to high load, so it’s definitely not as finely controlled by hand as a hydraulic needle valve controlled dyno.

@Dieselshawn @Red97 @malk315

Any input on your style dyno and how they react when passing peak torque? Or say 7 to 8k rpm on a modern saw?

I would guess similar happens, but am interested in how the different brakes are to operates.

With my brake and marginal water supply I use. The faster they spin the better.

Mine takes a lot of valve to get the high tq low rpm saws down to 5k. But anything above 8k is very minimal valve.

 

[Sawrain]

Thanks for the info, different behaviours between brakes it appears.

Please excuse the shoddy setup, as I said, it is just proof of concept.

From the left is,

Alternator rotor excitation voltage (load control)
Chainsaw rpm
Resistor load bank voltage
Power from alternator in Watts

Saw sounds a bit lean, but would four stroke if I reduced the brake load to zero, there was enough load at the start just to clean it up.

load sweep from 12k to ~6k
Current would max at around 77amps.

Alternator is a standard 100 amp unit, just had to remove the origional rectifier plate, as they are Zeners output was clamped to 20 volts, have since seen 150v.

The regulator is also bypassed, being fed 0-14v to control load.


It’s not really any use at this stage, but it has some ideas flowing.

Edit, that’s probably enough on this for someone else’s thread.