New 2.5 cc Model Diesel design and build.

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Thanks John for consolidating the pages.

Gave the "Holly Buddy" another run this afternoon and the getting better with each run scenerio seems to be true, this was the best I've seen so far, 9660.

Maybe 10000 with this prop is not outside the realms of possiblity, my Owen Mate Mk2 gave 9500 on this prop so I am very happy with its performance so far. Bear in mind though that the Owen Mate is just 2cc - the Holly Buddy is 2.5cc.

It is handling very nicely, easy to start both hot or cold, in fact hot is even easier. It must be getting close to being run-in about 6 to 8 x 3 minute runs now.

Hi Ed, nice engine and good build log. Many thanks to both you and Steve Jenkinson for most generously making the drawings available.
Regards, Steve
Hallo Ed

Thank you for sending me so soon the drawings from your engine.The Holly Buddy 2,5 model diesel engine you made is looking great and runs great as well.I saw all your selfmade model engines you and i must say you are a real well skilled engine builder with much knowledge about constructing small model engines.
I like your engines very much.

many greetings from modelmotor-The Netherlands-Europe.
You are making much better drawings than I do at the initial stages.
How will you ensure that the liner screws in so the gudgeon pin is well clear of the ports, or maybe it doesn t matter in your design.
I like either to leave a very small shoulder between the crankpin and web, or to make the big end slightly thicker than thhe rest of the rod, so there is no chance of the rod rubbing on the web, a few thou only is ok.
Hi Edholly, Great to see someone designing model aero engines,I have been inspired by(but not yet committed to start) by Chris Boll's designs.
I will follow you build ,please more photos and CAD drawings.
wow great build. you guys do good work one day ill be able to do such good stuff. love the builds , seeing what everybody makes and the awesomeness of the skills. it inspires me more an more.
I would like to acknowledge the award by HMEM of build of the month for the Holly Buddy. There are a great many other engines that I think are just as deserving as this one, so I feel very honoured to have it awarded to a fairly simple design and relatively easy build.

I last ran this engine a little while ago and did get 10200 rpm consistently with equal parts castor oil / kerosene / ether and some DII. Trying some less quantity castor oil and equal parts ether and kerosene and no DII fuel just now, it is down on this power slightly, but the fact it did achieve over 10,000 rpm was very pleasing.

I would like to thank Steve Jenkinson again for doing the plans in CAD in a way that I think is very easy to understand and not so easy to make mistake from. I would also like to thank David Owen to whom this engine is dedicated for his help and encouragement when building an engine was still a daunting task.

Hallo Ed
Congratulations for receiving the award by HMEM for the build of the month for the Holly Buddy 2,5 cc model diesel engine.The concept you designed is a great looking engine that probably can be build by many modellers all over the world.The fact that you choose of a model diesel engine will bring old times alive.

many greetings from Gerard- modelmotor-The Netherlands-Europe.
Hi, great project thanks for posting ,will we see the finished motor running?
Hi Ed,
I can't find a 3.6mm PAW spraybar. Would it be possible to measure the relevant dimensions so I could make my own.
This would be my second build so I do not have much experience in these things.
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Here is the PAW NVA.

Length of threaded section 12.5mm ; overall length this component 27mm ; diam where holes are 3.55mm ; inlet holes (2) are 3.9mm from fixed end and staggered maybe .5mm ie one is 3.6 and the other 4.1 from fixed end and the 2 holes are not diametrically opposed but are 90 degrees apart. I think you can work out the other bits needed from the photo ...


Hallo Steve,
Your Holly Buddy 2,5 cc model diesel engine looks great to me.You made the engine in the right way and style so you might be very proud of it to reach such a high level .
My congratulations for you and your very nice finished engine project.
many greetings from modelmotor-Gerard-The Netherlands-Europe.
Hi Steve,

You have made a wonderful job of building the engine - it looks superb in the photos and in the way it runs in the video you posted. Congratulations, you should be very proud of your efforts.

Kind regards ... Ed
Hello Gerard and Ed,
Thanks for your kind words.
I ran the engine again today. I'm still running it in . Having very little experience of these engines every start is a learning for me.
I really would like to design my own engine but I just don't have the required knowledge.
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Hello all.
Having recently finished the engine I found myself with a desire to design my own engine based loosely on Eds "Holly Buddy" and David Owens "Owen Mate". That is a Front Rotary Valve (FRV) engine that would be relatively easy to design and build for a beginner like myself.
Immediately I came across a rather big stumbling block. That being, I haven't got a clue what I'm doing. ��
So I decided I would reverse engineer Ed's engine. Starting at the beginning I thought it might be prudent to understand the port period angles, that Ed mentions in the introduction, that come with the drawings ie 107° transfer period, 122° exhaust period and 140° intake period.
I spent two evenings trying to come up with figures that matched Ed's. I failed miserably. I then got in touch with Ed who confirmed that his figures could also be wrong.
I then searched Google for "2 stroke port timing calculator" and found myself on Ron Chernich's fantastic site. To find the calculator, in the yellow bar on the left, click resources, design centre, Front Rotary Valve (FRV)
I entered all the required dimensions and the calculator spat out the timing diagram.
I then sent a message to Ed with the timing diagram. He has asked me to include it here for completeness .
As I stated earlier I'm very much a beginner. If anybody spots an error can they please correct it here.
Steve ( on behalf of Ed)


Port Diagram1.jpg
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Hi to all,is it possible to convert the B/Holly to a glow plug version as I would like to use it in a aeroplane, diesels vibrate a bit to much!! I understand a compression ratio of about 8to1 is required any advice or suggestions would be very much appreciated many thanks Keith

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