# 1936 midget engine



## whitehouse260 (Jan 18, 2018)

I recently purchased a midget gas engine built from plans in the 1936 popular mechanics magazine. My question is does this design call for a hollow crank shaft? Has anyone ever heard of a hollow crankshaft? When I say hollow I mean you can see all the way through. I will try to get a picture of it soon.
Thanks,
Matt


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## whitehouse260 (Jan 18, 2018)

Here are some pictures, the crank looks like it was made aas 2 halves I'm thinking I will press/solder a pin into the hole in the crank pin on onside to help with alignment and hopefully to keep it from binding up.


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## stevehuckss396 (Jan 18, 2018)

hollow crank wouldn't surprise me.

Is the plan to repair and restore? what condition is the engine in?


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## whitehouse260 (Jan 18, 2018)

I guess the plan for the moment is to repair, will the hollow crank affect it running? The auction came with a half finished crank, I'm not sure why he stopped maching it. it's not bent but I'm away from my my machines to finish the crank.


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## Hopper (Jan 19, 2018)

Your crank looks completely different from the original drawings seen here https://books.google.com.au/books?id=otsDAAAAMBAJ&pg=PA1349&source=gbs_toc&cad=2#v=onepage&q&f=false
page 787 onwards in PM Nov. 1936. 
Maybe someone was making their own version from several pieces instead of the original casting. The hole up the middle would be for alignment in assembly as you say. If left unplugged, the crankcase will breathe in and out through the hole on each stroke, which could get kinda messy!

Those old magazines are great reading. Whole different world back then. And so much more content than magazines today. People actually got a month's worth of reading in each issue!


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## whitehouse260 (Jan 20, 2018)

more pictures incoming... the guy who built it made the head out of brazed together scrap steel only problem is he didn't leave enough room to tighten the plug lol


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## whitehouse260 (Jan 20, 2018)

one question i have though is will the 2 half crank really matter that much??? there are many designs of engine that have an overhung crank on a bearing so will having 2 of those joined in the conrod big end hurt? also the connecting rod is brazed together when im home for spring break i will probably make a new on my cnc mill along with finishing the original crank.


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## Hopper (Jan 21, 2018)

Looks like a nice little engine and worth persevering with.

I should think the two piece crank would work OK. Seems to be done on plenty of other model engines. Silver solder should stand up to the rigors of demonstration running etc.

I'm sure I've seen somewhere drawings for a four stroke with an overhung crankshaft, with an extension on the crankpin driving another overhung crankshaft half that delivers drive to the timing gears. Saves having to get perfect crank alignment I guess.


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## whitehouse260 (Jan 22, 2018)

Ok thanks for the advice!


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## ddmckee54 (Jan 24, 2018)

Most vintage model engines, 2 strokes anyway, had hollow cranks.  I see that this is a 4 stroke, maybe this engine was built from parts of other engines? 

Don


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## Aerostar55 (Feb 17, 2018)

whitehouse260 said:


> more pictures incoming... the guy who built it made the head out of brazed together scrap steel only problem is he didn't leave enough room to tighten the plug
> 
> 
> I have the drawings from the magazine for this engine.  I don't see why a hollow crank shaft wouldn't work fine.  The drawings show a solid crank machined from 1/2" bar stock.  It's actually pretty easy to make, a straight forward turning job.
> ...


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## Aerostar55 (Feb 17, 2018)

whitehouse260 said:


> I recently purchased a midget gas engine built from plans in the 1936 popular mechanics magazine. My question is does this design call for a hollow crank shaft? Has anyone ever heard of a hollow crankshaft? When I say hollow I mean you can see all the way through. I will try to get a picture of it soon.
> Thanks,
> Matt



Where did you get it?  These engines turn up on ebay or model engine shows from time to time.  I know of about 5 that I have seen over the past 4 years or so. They do run pretty good.


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## whitehouse260 (Feb 18, 2018)

It came from ebay. The seller included the patterns and a casting kit for the wall water witch.


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## Aerostar55 (Feb 19, 2018)

What needs to be done in order to get it running?


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## Aerostar55 (Feb 20, 2018)

You have additional castings for the Wall 
Water Witch?


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## Aerostar55 (Feb 20, 2018)

I have drawings for the Midget engine that were
Published in Popular Mechanics


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## rockets (Aug 7, 2018)

"I'm sure I've seen somewhere drawings for a four stroke with an overhung crankshaft, with an extension on the crankpin driving another overhung crankshaft half that delivers drive to the timing gears. Saves having to get perfect crank alignment I guess"

ET Westbury's Whippet is designed in this fashion.

Regards,
Rockets


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## Aerostar55 (Aug 16, 2018)

I have the original drawings for the Midget engine that you have.  Do you plan on building the Wall Water Witch engine from that auction?


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## Aerostar55 (Sep 13, 2018)

whitehouse260 said:


> It came from ebay. The seller included the patterns and a casting kit for the wall water witch.


The Wall Water Witch is my favorite little engine.  I have original drawings for it.  I also have the original
drawings and magazine article for the Midget engine that you bought.  Maybe we could do some sort of a trade? I can help you with parts or information on that Midget engine.


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## Bob44 (Sep 14, 2018)

I think it's called a follower crankshaft. A couple engines in the Home Shop Machinist magazine uses them including the Rupnow 4 cycle. I had my doubts about it but it works fine. 
Also 2 cycle model air engines with rotary intake valve use a hollow crank. 
Just my .2 cents for what it's worth.


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## goody (Sep 17, 2018)

All of my .049 glow engines have hollow cranks, induction port, I know there were some that were reed valve inductions.

Pat


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## Brian Rupnow (Sep 17, 2018)

I have built a couple of 4 cycle engines with a two piece crankshaft (leader half and follower half) and they work fine. Some two stroke engines had hollow crankshafts as part of the induction system.  I can see no reason to have a hollow crankshaft, but I wouldn't apply heat to try and solder it shut. Just make a plug from aluminum or brass and epoxy it into the open end.


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