Holly Buddy Build Register

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Sydney Australia
Project of the Month Winner
Jun 14, 2013
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Sylvania, Sydney Australia
I know there have been quite a few Holly Buddy's made and thought it would be great to have a register of them and those engines based around it.

As it was HMEM where I first wrote up the build of the prototype, would be good to have a listing of completed builds here. Maybe a few photos and a brief description and a number for it accounting for those written up prior.

So I'll start with the ones I have made.

Couple of things I'd like to mention.

Firstly the name Holly Buddy is a nod to the Owen Mate by David Owen whom I have the utmost respect for and who helped me immensely in the early days. RIP David.

Secondly thanks again to Steve Jenkinson who did the CAD plans for it - and many little tweeks to make sure it was as unambiguous as possible.

Thirdly thanks to Outerzone for hosting the plans, not only for the Holly Buddy but a whole host of model engines.

Fouth, thanks to Maris Dislers who tested the engine and wrote and article that was published in our wonderful Aeromodeller Magazine.

Finally here is the .pdf file that started it all.



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1. The prototype. The first one built.


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2. The Mk2 version. Made using a pattern and then a casting which I had hoped to be able to supply at reasonable cost, but it turned out to be rather more expensive than I had hoped.


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3. An inline twin version, basically 2 Holly Buddy's joined together - the crankshaft feeds the 2 crankcase cavities though inlet ports in the crankshaft 180 degrees apart.


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4. Holly Buddy Opposed Twin. This one is 2 Holly Buddy's opposite each other. It cheats a bit and uses the cheeks of the intermediary bearing as much as it uses the bearing itself. Figured no worse than running an engine as a pusher where the prop driver runs against the crankcase in a plain bearing motor. Has worked out fine. The static photo is as it is now with the inlet vertical.


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5. Holly Buddy Mk 3 ... Wanting to make it look a little prettier - uses screw threads to attach nose, backplate cylinder and muff. Screws at the rear also hold it from turning. Looks totally different but it is the same inetrnals - just different clothes !


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