Scale model Economy hit & miss engine builders wanted

[JasonBModerator @jasonb]

The above weighing method just goes to show that what I said about an alloy conrod and piston will help as this gives a lower value for P.

 

Jason

[Charles 2010Participant @charles2010]

Hi Jason

 

Yes all coming together …

 

This is an amazing forum with so much information coming together  in a relatively short time and the fact that members are prepared to share their knowledge with others.

 

Regards Charles

[Charles 2010Participant @charles2010]

The engine run this morning revealed that even adding the small amount of additional weight to the web, as shown in the picture a few posts back, considerably reduced the vibraton to an extent that is very tolerable and I can not press on with improving other items :-

1. the slow running  it is still too fast

2. checking the carb as sometimes the fuel line empties so the non return valve is not working properly

3. drill small holes in the oil cap to allow them to vent which I missed noting was on the drawing.

4. ETC ETC

 

Regards Charles

Edited By Charles 2010 on 17/12/2010 12:19:23

[Ian S CParticipant @iansc]

I think its a general problem with small motors,  getting them to run slowly. possibly the relative weight of the flywheels are not enough in the small scale.  The ideal flywheel for a little motor like this I think would require an over scale size to keep he speed down.

Full size idle would be less than 200rpm (I’v never checked). Ian S C

[Charles 2010Participant @charles2010]

Well the light spring is too light so the speed control has to be at MAX to keep the engine running but at least I have something to work on .

 

The engine was run for about 20 minutes to day and all went well. I was able to use a engine ignition strobe light  and my markings indicated ignition 5 deg AFTER TDC .. So the engine may run even better with the ignition move to TDC or a little before as suggested in the plans 8 to 12 deg BTDC.

 

Still too cold and family here so that will be sorted another day.

 

The revised keyways are holding firm as they are of the Gib type I think it is called and driven in tigtly but still with a space to be able to remove if needed …

 

Regards Charles

[Gordon WParticipant @gordonw]

Balancing a single cyl. is not possible, all the previous information is good. I’m a bit reluctant to post this, ‘cos I will get shot down, but:_ An easy way to get some sort of balance is to weigh the con rod and piston, then take ,from 1/3 to 2/3 of this weight, depending on what you think will be the best. Get some lead strip the same as your decided weight and wrap round the crankpin. Then balance as a wheel. Good simple formulae for balancing in Tuning for Speed and Speed and How to Obtain It, both old M/cycle books

[Charles 2010Participant @charles2010]

Well today the engine had a nice run ….  The carb setting was found to be a bit rich so it was turned down a little but this ment that the engine did not pick up after a miss ….  So I must look into the chicken feed tank arangement mentioned previously…

 

The spring for the speed control is back to the original one again and now that the engine is well past if first hour of runing gives good responce.

 

I am going to change the water drain to a right angle bend and bung to make draining after a run easier.

 

When that is all done and the engine proved to still run well I will be fitting a generator that I have been loaned with the aim that the electricity generated will run my “G Scale” garden railway …  Of course there will need to be a control box  but let’s get it generating first.  If that fails then I am thinking  of making a water pump to supply water to  a garden feature which would also have to be made !!!!

[John OlsenParticipant @johnolsen79199]

Gordon, that sounds pretty good to me. Tuning for Speed is available as a free download in the Interwebs, dunno if it is supposed to be or not.

 

What I did with my steam launch engine, I realised that  I was not going to be able to get enough weight to balance to anything like a reasonable proportion, so I just crammed in the biggest weights that would fit. Being a compound twin with the cranks at 90 degrees and the pistons being very different in weight, there was no way it would be possible to do anything very scientific. Anyway, the results are perfectly good, it does not dance around significantly at any speed that it is reasonable to reach. I have had it up to 600 rpm on a tachometer.

 

 

regards

John

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