Anybody have plans for building a kart engine DYNO?

[Terry Sullivan]

Anybody have plans for building a kart engine DYNO?
I've seen ads in old magazines for kart dynos. I believe Go Power used to sell dynos or plans for dynos.
Any plans or designs would be considered.

Terry
terryas@att.net
678.617.0730

[Gordon Duax]

I have built several hydralulic dynos that are very accurate.
But the hydralic components to do it right are not cheap.
And because that most hydraulic pumps can not take high rpm, they need a reduction from crank speed.

The unique thing about going hydralic, is that with the correct valving, you can take a reading either across the full rpm band,
or set the RPM, and make a run, shut down the engine, make changes (pipe, reeds, timing, etc.), fire the engine back up, and the engine will go right back to the same RPM, and the dyno will show just the change in power.

We even did one with a servo valve, controled by a PC, with pressure inputs, engine rpm, and secondary rpm to the PC.
it would map clutch slip.
It also had a flywheel on the secodary shaft to simulate kart inertia.
The flywheel was sized for the lightest kart, and had weight adjustment disks of .040" sheet steel so that we could simulate heavier karts.
And with the valve being controled by the computer, and a servo motor working the throttle, we could even simulate laps at different tracks.
This was at least 18 years ago, and I would have to dig to see if I have any paper work left on it.

You don't have to get that fancy on one, a manual compensated flow control valve will work just fine,
That is what I used on my personal dyno.

Then it is just a matter of recording pressures at different rpm ranges, and figuring them back through normal hydraulic formulas.

I have seen other hydraulic dynos that just use an inexpensive non-compensated flow control valve, but they are not as accurate.
Like anything else, garbage in is garbage out.

[Scott Kneisel]

Hey Terry,
I work in a lab where we test electric motors on various dynamometers. We have various size dynos and they all work on magnetics. The dynamometers utilize a load cell to measure the torque on a lever arm and a rotary encoder to measure the speed. The magnetic brake develops calibrated drag as the electrical current is increased. This is a real nice system all controlled by software that we wrote ourselves using Labview graphical language. So everything is there to do the job except I don't think that the largest dyno we have would develop enough drag for a Mac or other racing engine. I am also sure that my place of work wouldn't appreciate a Mac screaming in out nice laboratory not to mention the exhaust. These brakes are all I would really need to build my own dyno but they are REALLY expensive so even though I have penciled out a design using two large magnetic brakes hooked shaft-to-shaft, the money required to make it happen is prohibitive. Better to sent the engine to Comet and have them run it.

The hydraulic dyno Gordon is talkng about is something quite interesting to me but I really do not have much knowledge about these but will see what I can find out.

Another intriguing prospect is an "Inertia Wheel" dynamometer. Basically all you need for one of these is a large (well balanced) inertia wheel, a rotary encoder or tachometer generator and software. That is it.
The principle is that with a known inertia, you can calculate the torque to accelerate the inertia as long as you know the time required to accelerate the wheel to a target speed. Using this principle, you can start at a slow RPM and accelerate to a higher speed and calculate, measure and record that torque, then accelerate to a higher RPM and calculate that torque and on and on. The software for this is already developed and can be purchased or maybe it is freeware, I can supply the speed monitoring equipment and now all I need is a really big flywheel on some killer bearings. It might be a little scary though to have a 20-50# flywheel running at 15000RPM. I think balance is critical.

Anyway, sorry for the ramble but as you can probably guess, I have been thinking about this for a long time. I will keep looking.
Scott

[Rob Voska]

If you build an inerta dyno use a 1 way bearing to drive it. Most engines are hooked up direct drive. That way if you hurt an engine it free-wheels to a stop. I would also think about a semi flywheel and have it rebalanced. Along with a foot operated disc brake to stop the monster.

[Scott Kneisel]

Right on Rob,
Great suggestions, I'll bet we could use an old Hurst kart brake.

I never thought of the freewheel thing, that could really tear up the engine if it was just hooked up direct without a one way... it would have to be a pretty robust one way bearing, I am sure big ones are abailable.

Would you volunteer to make the flywheel on the Hardinge!! It certainly is big enough. Only kidding.
Did you get the monster up and running?
Scott

[Tom Smith]

Palmini small engine dyno .jpg

(73.29 KiB) Downloaded 1387 times

Palmini dyno pump and torque arm etc, they look similar to a kart gear drive unit. McCulloch used these dynos for quality control purposes. Every so often they yanked a powerplant off the production line and dyno tested them.
GEM, Wiseco, and probably other engine building shops like Russell etc. used Clayton small engine dynos.
From what I know about modifying 101s and running them on GEM's dyno, they were about wheezed out at 23/23.5 hp at which point the head and the top of the cylinder drifted off the crankcase.
Russell claimed 39 hp from the best modified but still legal B-Bombs in the old days. That translates to probably 45 hp today.

[Scott Kneisel]

Chris Marchland just sent me this eBay #260525381368
It is a snowmobile dyno but will probably go for big bucks. Check it out!!

[Brian Thomas]

Please excuse my ignorance on this dyno issue . As far as an inertia dyno goes,, why couldn't a person use a large automotive front wheel tire hub and brake asm. and run it using a jack shaft to run it then run the oneway bearing on the input of the jack shaft .
You could make gearing changes at the jack shaft and would not have to spin tire wheel and hub asm. to any great speed and also they can be balanced . You would also have a large brake asm. to shut it down .
Just a thought from a the gallery
Brian

[Scott Kneisel]

Interesting idea Brian.
The issue I see is that if you gear "down" the speed of the tire/wheel assembly you reduce the inertia considerably. In a rotating body the inertia varies as the square of the speed change so say you were to gear down the inertia wheel 5:1 to get the speed reasonable then you would be reducing the inertia by 25 times and it probably wouldn't be enough to be effective.
I like Rob Voska's idea of getting a semi truck flywheel and having it balanced. That might be easier.
Good thinking though, if you dared rotate a tire wheel assembly 15,000 RPM it would work. I think it would come apart though.
Hope you have a Merry Christmas, I need to get wrapping!!

[John Miller]

I seem to recall some form of an article on a Kart related Dyno located on the "Vintage Karting Archives" site. I did not read the article & can not comment upon the information provided.

On another note... Is reference to, or direct links leading to, either the "VKA" site or other Kart related sites, welcome or not on this forum?