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Engine test rig

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Stevo23/08/2014 17:49:50
2699 forum posts
419 photos

Hi all, I do rebuild and restorations on glow engines, and I have a basic test stand that I bolt to the pergola in the garden. So far so good.

I want to develop that much further, driven both by the need and 'because I can' ! Sounds a bit complicated, some will say overkill !

So my thoughts are: -

  1. The engine must be capable of being mounted upright, inverted, and at 90 degs.
  2. The throttle will be driven by a Joystick (Thanks Mr Whybrow) and via a servo. It will be PIC Controlled and Iv'e written most of the code already.
  3. Tank level should be adjustable for CL of the carb
  4. It will have an inbuilt glow panel
  5. It will have a built in rev counter
  6. I would like to measure the head temp as well, but most of the temp sensors only go to 125 degs. C
  7. It will have an emergency stop switch similar to throttle cut on a Tx where it reduces the throttle to minimum -10%
  8. Perhaps some form of time for breaking in engines, i.e. 5 mins running then 5 mins cool off
jeff2wings23/08/2014 20:25:58
avatar
809 forum posts
1989 photos

Sounds like a good project yes ,I could do with some thing like this for running up some engines in my collection , will give it some thought as screwing them to a workmate is a pain ! laugh

Stevo23/08/2014 20:36:21
2699 forum posts
419 photos
Hi Jeff, look forward to it

My main factor was to test the engine other than upright. And on the stand, there is a difference between in inverted installation and an inverted aircraft!!
Stevo27/08/2014 17:55:41
2699 forum posts
419 photos

Started a little bit on the electronics.

The HobbyKing tacho is only 4 digits, and the extra or trailing zero is 'implied' I wanted a real one.

et 2.jpg

So soldered up a 0.36" red LED display and series resistors...

et 1.jpg

Which gives me a trailing zero.

 

Add this alongside the main display..

et 3.jpg

Yes it sits high, but put a difusser over it and only I will know...

et 4.jpg

So all finished..

et 5.jpg

Thanks to Martin Whybrow, here's the joystick with modified leads..

et 6.jpg

So back to the breadboard for the main testing...

 

et 7.jpg

Edited By Stevo on 27/08/2014 17:58:43

Martin Whybrow27/08/2014 19:21:25
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884 forum posts
33 photos

Good to see you've already got it hooked up!

Stevo30/08/2014 17:37:23
2699 forum posts
419 photos

Development now well underway. Sorry if I talk electronics, but there's a bit involved. Won't be long before I move on to the machanics!

Cut a long story short, I was snookered by the fact that the Joystick does not travel the full range of the pot. Anyway, rectified that and sorted out an analogue front end, a range of op-amps with adjustable gain & offset.

Net result is 0V at low throttle, +5V at full throttle. There is an adjustable pot for the idle, which will open the servo around 0-20% to set an idle - only when the joystick is at low setting of course (liken it to a throttle cut on some digital Txs). All will eventually become apparent!

Test diagram

et 8.jpg

The analogue breadboard

et 9.jpg

et 10.jpg

 

Edited By Stevo on 30/08/2014 17:40:59

Simon Chaddock30/08/2014 18:22:54
avatar
5776 forum posts
3055 photos

Put in a load cell and actually measure the thrust as well. wink 2

Stevo30/08/2014 18:24:06
2699 forum posts
419 photos

Now yer talkin' wink

Stevo30/08/2014 18:40:51
2699 forum posts
419 photos

Ok Gauntlet thrown down... Looked at a few load cells etc, but probably far more easier to use something like some digital scales or suitcase scales with a display I can remove and put in a panel.

Thoughts anyone?

Plummet30/08/2014 18:50:32
avatar
1419 forum posts
41 photos

The cheap Aldi verniers will measure distance for you. Make the mount pull against a spring and the vernier could measure distance = force.

Plummet

Stevo30/08/2014 18:53:44
2699 forum posts
419 photos

Thanks Plummet! Yes that's one way.... Calibration could be a bit of a problem.

I fancy disecting some luggage scales...

Engine Doctor01/09/2014 11:48:42
avatar
2591 forum posts
40 photos

Hi Steve what engine size are you intending to go up ? If its not too big then a set of cheap kitchen digital scales go up to

5Kg and are very cheap at aldi. (when they are in stock

Stevo01/09/2014 18:09:52
2699 forum posts
419 photos

Hi Phil..probably up to 120 size maximum. Disecting some scales maybe an idea!

Now, a prize for anyone who can accurately say what this bit is for. The brass head diameter is 12mm, copper pipe is 5mm OD...

et 11.jpg

Edited By Stevo on 01/09/2014 18:13:38

cymaz01/09/2014 18:13:44
avatar
9334 forum posts
1211 photos

Golf tee?

Dave Hopkin01/09/2014 18:20:47
3672 forum posts
294 photos

Easy peasy Stevo

Its a device for performing prostate examinations on really small dwarves.......

Stevo01/09/2014 18:27:20
2699 forum posts
419 photos

<grin>

Nope not even close cheeky And I don't play golf...

cymaz01/09/2014 18:37:21
avatar
9334 forum posts
1211 photos

I've got it!

Ice cream scoop

Stevo01/09/2014 18:38:36
2699 forum posts
419 photos

For a midget?cheeky

 

HINT: the material is non-ferrous for a reason!

Edited By Stevo on 01/09/2014 18:41:54

kc01/09/2014 19:42:17
6646 forum posts
173 photos

Hydraulic part of your dynamometer?

Stevo01/09/2014 20:35:12
2699 forum posts
419 photos
Nope...
Nice try Keith !

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