Author Topic: How do you test you engine builds  (Read 2796 times)

Offline geoff5269

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How do you test you engine builds
« on: September 05, 2013, 03:55:00 PM »
I thought i would share this method i have used to test the efficiency of my latest engines. When my new build is completed i run it on my small compressor which has a 3 litre tank and is a favourite for air brushing. I charge up the tank until it turns off and then run the engine at 5psi and time how long it will last on a tank of air. also i try to run at a lowest pressure to see how easy they turn. This has worked well but i did find that when you start at 5psi as the air runs down the pressure starts to rise and you have to constantly adjust it . So i came up with the idea of adding a second regulator with the first one set at 10psi and the second one set at 5psi i now get very constant output.
some of my simple engines have run from 9minutes to 20 minutes on on charge of air. I find this a very useful exercise and you can compare results if you make any adjustments to the engine.    I will add a few pics showing the results.
Geoff

Offline smfr

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Re: How do you test you engine builds
« Reply #1 on: September 05, 2013, 04:40:18 PM »
Neat idea, and some lovely engines you're testing there  :ThumbsUp: :ThumbsUp:

Out of interest, where did you get the second regulator that fits the airbrush compressor fittings? I need to get one for mine.

Simon

Offline steamer

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Re: How do you test you engine builds
« Reply #2 on: September 05, 2013, 04:49:07 PM »
"When in doubt...measure something!" is a motto I use in in professional life all the time

I think this is a great way to to start to test a model engine.    I wonder how the bore and stroke can be factored into the test results?

Air consumption will increase with the square of the increase of the bore and directly with stroke....with two different engines sitting side by side.

It should be pretty easy to account for the air consumption ( using Boyles law) to determine the amount of air at the point of cut-off...and from there you should be able to develop a theoretical idicator card.....any excess...is leakage...which could also be used as a metric for performance.

From there it could be analyzed like the full scale bretherin.

Thoughts?

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline geoff5269

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Re: How do you test you engine builds
« Reply #3 on: September 05, 2013, 07:48:05 PM »
Simon
Theres a lot on Ebay in the U.K.and they are surprisingly cheap i even saw them at my local tool emporium, and plenty of gauges of various values. You need to check which thread you need which can be a bit confusing as it refers to the internal bore, the small thread is BSP 1/8" which measures approx 3/8" outside and the next  size is BSP 1/4" which measures 13.2mm or a bit over 1/2" outside.
I must say i was very pleased to now have this constant air pressure when i am videoing the engine running as i like to hear the sound it makes and not have the compressor click in half way through.
Hope this helps
Geoff

Offline b.lindsey

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Re: How do you test you engine builds
« Reply #4 on: September 06, 2013, 02:13:08 AM »
 Goeff, i get the same thing when letting the reservoir empty...the regulated pressure goes up on its own. Could someone explain this? Is it a mechanical aspect of the regulator, or a function of the air itself?

Bill

Offline Bezalel

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Re: How do you test you engine builds
« Reply #5 on: September 06, 2013, 04:44:12 AM »
Goeff, i get the same thing when letting the reservoir empty...the regulated pressure goes up on its own. Could someone explain this? Is it a mechanical aspect of the regulator, or a function of the air itself?

Bill

I'm also curious.

It maybe that the regulator needs a minimum differential pressure across the regulator to be able to regulate the output.

What Bill said - can someone explain?

Cheers

Bez
Queensland - wet one day, humid the next

Offline geoff5269

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Re: How do you test you engine builds
« Reply #6 on: September 06, 2013, 11:47:22 AM »
Hi Bill
I think it must be because when the tank is fully charged the pressure is 60psi behind the regulator but as it runs down the regulator relaxes and allows more air through. I took a chance in fitting a second regulator but it works perfectly. I hope to add a video collection so you can see them running.
<a href="https://www.youtube.com/watch?v=6XSgOso9GDU" target="_blank">http://www.youtube.com/watch?v=6XSgOso9GDU</a>
Geoff

Offline lakc

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Re: How do you test you engine builds
« Reply #7 on: September 06, 2013, 12:05:28 PM »
Assuming you can get your engine builds running ;D This is my IC engine test bench.

The bottom flow meters are used for gaseous fuel (propane), the upper airflow meter and manifold can be set up for compressed air.
The switch in the upper left powers the little black box with a knob, that is a pic microprocessor controlled servo driver for the throttle.
The plastic valves on the left allow selection and filling of various liquid fuel sources. Hanging off the top backside is an old lawnmower tank currently filled with E85.
The cut up yardstick and tubing on the right is a homemade manometer, and the metal valve block at the top allows selection of various measuring points.

And for safety, we have a substantial 1/8" steel propeller shroud for working on airplane engines.
I have spent enough time working around a dyno to respect spinning things. The hole in the cinderblock wall where a chunk of mallory came out of a crankshaft was a constant reminder.
There are a million holes in it as it has been constantly reconfigured for different engines. There is even provisions for an airflow sensor to be added.
Jeff

 

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