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Hot-Bulb Semi-Diesel Plans Wanted

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weir-smith

Bruce W-S
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Steamchick

Re gears

What I thought would be a simple task has proven to be quite difficult re suppliers of suitable gears. I haven't been able to track down the US supplier but will keep looking as I will have it some where. The price delivered to Australia was $96 Aust and that was two and a half years ago. The postage represented about a third of the cost but that is life.

The Chinese supplier seems to have disappeared off Ebay however, I found another source - see attachments. I found these on Ebay out of HK so I hope it helps.

Bruce W-S


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Richard Hed

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Hi Bruce, I like your test engine. Very conventional arrangement. I wonder - did you buy your gears for the valve drive/cam shaft drive? I have been looking and can't find any commercial gears at 2:1 ratio, and do not have the tools and ability to cut them. Ta,
K
I thimk you have the ability, just not the tools
 

kuhncw

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Debolt Machine in Zanesville, OH, lists set of helical timing gears and a couple others for model engines.

Chuck
 

weir-smith

Bruce W-S
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I have spent some time looking up info re hot bulb engines and there is not much about. There are a couple of links which you may find of interest:

Hot Bulb and Glow Plug Difference | Model Engineer

This article gives a good run down on the operation of the hot bulb engine.

The next link has photos of some models that have been built

Alyn Foundry Home Page

The next link is to a book primarily about the design of early diesels however it may also go through the theory of hot bulb as they were the for runner of the compression engine (diesel).


From my reading on the subject, the principal looks easy enough. Everything is low pressure so no real problems with the fuel pump and injector. It should run OK on kero or lamp oil which is cleaner. I would look for an engine that appealed and then draw it up with what ever process you have e.g. CAD or pencil and paper. There are plenty of four cycle hit and miss engine plans out there so just grab one of those and use it to get the basics right. I wouldn't have a cylinder bore of more than 1 inch. The hot bulb, I would make out of cast iron round and the injector can be brass. You only need to spray a very small amount of fuel into the hot bulb so the fuel pump will be of the jerk type which is quite simple to make. To control the speed, you can use a sliding wedge between the pump piston and the cam. The cam will need to have a reasonably sharp lobe to provide a short sharp injection. The injector can be of the popit valve type or needle
valve type. Have a good look at some of the photos of Fine Hanson's engines as he has done quite well in this regard.

Hope this helps

Bruce
 

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