Little '36 Midget Build

[Dave Otto]

Beautiful engine Jason.

Dave

[Johnmcc69]

Mike was thinking the same as i..with the jar turning.
 I see how it works now.

 Give it up. Give us the shop tour.

 We know you have some shiny new toys.

  Beautiful work Jason, whats next?

 John

[Flyboy Jim]

Did not show the workshop as I thought Jo may be offended by the sight of those couple of useless far eastern machines that keep on making these engines

 

Jim

[MJM460]

Hi Jason, that engine is a real work of art.  A beautiful job.

So the test stand needs some cooling provision?  I wonder if a computer fan with some ducting shaped from brass sheet to direct the air over the fins could be a part of the test stand to allow some longer runs and higher performance.  Leaving it as part of the test stand would avoid spoiling the beautiful appearance of the engine.

MJM460

[Craig DeShong]

Beautiful job Jason, and it runs like a dream!

[Zephyrin]

Great thread as ever, and beautiful engine, thanks to share.
I'm puzzled by the contact breaker in brass, in my experiences, this metal does not last long with a conventional ignition coil, but maybe the cutoff voltage is lower with CDI ignition?

[Laurentic]

And if I may ask another question Jason, of a practical nature, the heat treatment of the cams - could you elaborate a little on what was involved, harden and temper or just case hardened?  I hope to have a cam made shortly and was wondering how to heat treat it.  Thanks,

Chris

[Jasonb]

Will have a think about the shop tour although some of the tools are so new and shiny that I will have to hide them away as they are not available to buy yet, just evaluating them for a supplier

I was thinking more along the lines of the outlet from the shop vacuum for some high volume low pressure cooling though I have used the compressor in teh past to good effect with a steady flow into the water jacket of engines.

The CDI units from S/S that I use only need a tiny current as the contacts are little more than a switch, infact they use two of the three connections that a hall sensor would plug into and if you pass too much juice through those they just burst. So no need for tungsten points contacts.

The cams were cut from Silver steel (drill rod) which already has the carbon content so no need to add more by case hardening. Simply heat to 750degC and hold there for a minute then quench in water. Clean up an area so you can watch the colour change as you heat it again and when it reaches brown to light purple quench again. Job done.

Time wise this one was a bit slow, dates on the photos suggest a little over 3 months having taken the first photo on 7th July. I tend to spend a bit less time in the workshop during the summer as my other hobbies need a bit more attention at that time of year or the shed is too hot to work in. Some of the other 24mm bore engines have been running within a couple of weeks particularly those done over the Christmas - New Year period where I give myself some time off work so can get in some shop time.

j

[Laurentic]

Thanks for taking the time to detail those answers Jason, much appreciated. 

Did you experience any dimensional changes to the cams in heating them up?

Chris

[Jasonb]

To be honest I did not measure them after, possibly a slight increase in size but as that would most likely be even all round and only a micron or two not anything to worry about on this engine.

If it were a long camshaft with several cams you would have to be careful to quench it vertically as going in at an angle could bend it.

[Laurentic]

I'd hoped you'd say that!!!

[doubletop]

Jason

Nice job, again!!

 "Spectacular High Speed Performance", according to Popular Mechanics. You'll have to do another video and let it go.

Pete

[Jasonb]

I'd also have to revert to the original cam profiles and events to do that as I altered them to give what I wanted

[b.lindsey]

Another build I had totally missed Jason. Very nice little engine and it really runs well. Nicely done!!!

Bill

[Brian Rupnow]

Jason--what a lovely little engine. It shows great craftsmanship and is a great runner.---Brian