Engine Dyno Practise

[topcatproduction]

Hi all, first post here and joined as I have read another good thread on water brake engine dyno's and looks like a really helpful place!

I'm looking to build a really simple dyno and had a thought which I cant find anywhere! Is there any reason why you couldn't just mount the engine on a good frame, rig up a clutch of some kind, have a set length bar (say 5') from centre of clutch plate to a point on some scales and when you hold the engine at set rpm's, push the clutch in to engage and note the highest reading the scales go to. I'm assuming as the revs dip the load will slightly reduce so you could get an accurate reading? I know this would eventually burn the clutch out but only be a couple of seconds a time...

This way all you would need to do is multiply the reading by 5 (5ft bar) and you have ftlbs at set rpms to plot onto a graph.

Simple in theory but would it work?! I attached a very basic drawing.

Also all this talk of using truck eddy brakes- how do you take any sort of reading from them? I'm getting a bit confused!

 

[LionelHutz]

Depending on what you want the dyno to do, you could just use a big flywheel and measure the acceleration rate of said flywheel. As Pat already mentioned, there is always some error if you do not measure at steady state but if you are doing this for tuning purposes then it would suffice. You could use a proximity sensor and a cheap PLC with a high speed counter input to get accurate data.

 

[topcatproduction]

I would like the flywheel idea- but testing engines up to about 400bhp it would need to be so big it would be dangerous! The Rover V8 I last built and is in my current car is 370bhp and I want more...

Will look for water brakes

 

[gruntguru]

You could use the Earth as a flywheel and the car tyres to turn it. Use the crank angle sensor or ignition pulses instead of a prox ensor.

 

[MikeHalloran]

There's an iPhone app for that.



Mike Halloran
Pembroke Pines, FL, USA

 

[evelrod]

Yeah, I have an app that attaches to the front seat cover that seems to work reasonably well...and...it's free!

Rod ;o)

 

[patprimmer]

Rod

But is it large enough for that much power. ;-)

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[evelrod]

Oh, good lord yes.......

-----When I retired in 98 I was 185lbs. I zoomed up to 235 in two years and have now "slimmed" to a svelte 210 !!!


Rod

 

[topcatproduction]

Hey all, I have found a choice of 2 telma/eddy brakes, one is about 11" diameter, 12v and from a 7.5t lorry, the other is bigger at about 15" diameter, 24v and from an 18t fire engine, I cant find ANY information from the serial numbers etc, but could anyone hazard a guess as to what sort of KW each would be rated to? I'm thinking the bigger one should be ok- but not sure yet!

If I put a gear reducer infront then it will help absorb some power which is good- but dont want it to be too big a set up.

 

[Warpspeed]

Information on these Telma retarders is hard to come by, but this is what I have scrounged so far :

CC50, 368 ft/lb, limiting rpm 4500.
CC80 589ft/lb, limiting rpm 4500, rotor diameter 340mm
CC100, 737ft/lb, limiting rpm 4500
CC125, 921ft/lb, limiting rpm 4000
CC160, 1179ft/lb, limiting rpm 4000, rotor diameter 570mm
CC200, 1474ft/lb, limiting rpm 4000
CC220, 1842ft/lb, limiting rpm 3500
CC270, 1990ft/lb, limiting rpm 3500
CC300, 2233ft/lb, limiting rpm 3500

The only reason I happen to know the rotor diameters for the CC80 and CC160 is that I have a CC80 in my own dyno, and a friend has a CC160 in his.

 

[topcatproduction]

Thanks, unfortunately the bigger one is not a Telma, the only lettering appears to be IC or KC, but not seen it myself yet.

The smaller one is a Telma, CE30 12v which would appear to be much smaller, so you are actually running one in an engine dyno?

 

[Warpspeed]

My CC80 is direct coupled to some rollers and used as a chassis dyno.

 

[topcatproduction]

Does it work well with smaller and bigger engines? I wasn't sure how well a little engine would work on the same dyno as a big V8!

 

[Warpspeed]

This is a home dyno, used only for personal engine tuning use, on my own four cylinder everyday turbo car.
A dyno cannot really be too big, because you can turn down the load resistance right down to zero.

 

[topcatproduction]

Thanks.