Diesel Engine?


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7:35 AM
Sep 21, 2008

I am something of a newb. I just built my first gas powered two stroke bike as an experiment, and it has been working better han I dared expect.

However I have come up with a question...In general the power output of the HP diesel engines is aroud 2-5 hp. The RPMS if I understand correctly run from 6000 - 8000 rpm. I have not however been able to find the torque.

The reason I ask is that i have been looking to try and build a diesel version of the motorized bike. I am part of a biodiesel processing experiment at my local university and have a virtually unlimited supply of biodiesel at the moment. Looking around online, I came across these.

they are diesel model airplane engines that have an output of 2.8 HP at an RPM of 15000. It would require some special gearing probably to bring the RPM down to a standard 6000 for the bicycle, and to make a right angle turn to drive the bike chain, but these do not seem to be out of hte realm of possibility. Has anyone tried such a thing successfully yet?
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That model engine is not meant to burn diesel fuel. It is meant to burn "glow fuel" which is a mix of methanol, nitromethane, and lubricating oil. It would probably burn up if pushed to maximum output for an extended period.

For a small diesel, look for a small utility diesel. Changfa in China builds small, single cylinder diesels. (might still be a bit large for a MB)
Diesel model engines don't run the same diesel as other engines, IIRC they run ether in the fuel mix...

FWIW you may want to look into Davis Diesel Engines.....they do conversions of glow fuel engines into diesel....it may or may not be regular truck diesel as mentioned earlier....

I was going to experiment with one and have the smallest engine on a motored bike!...Of course you will have to gear them down considerably....I was looking into the nitro .21 engine with a pull start....the gear train would be huge compared to the little engine....Some of the race versions of the little .21 engine would probably make more HP the the HT engines....wow!...Please post pics if you do it....that sounds like a fun project!

Oh...I didn't realize you were looking at such big engines...Hmmm where's the challenge in that? HA ;-)

Model airplane 'diesel' engines run on methanol and nitromethane with castor oil or synthetic lubricant. They're also designed for limited lifetime - 15 minute flights times several hundred flights would not be much of a lifetime for a MB, maybe 1000 miles?

Did some research on diesel engines (run on true diesel fuel), and conversion of these kinds of model airplane engines, for the US Army a few years ago as portable power sources for the individual warfighter - batteries for the systems envisioned for Land Warrior, etc., were getting out of hand and my engineering consulting firm was asked to analyze alternative power sources for the individual soldier - diesel, alcohol, fuel cells, etc.

Turns out that small diesel fuel engines are very inefficient - I don't remember the exact numbers, but something like anything below 5 horsepower or so became real fuel hogs and hard to maintain combustion. There is a company that's been working on improving efficiency for years, without any real results (at least as of 4 or so years ago when I was involved).

Smallest i see available (thru a short google search) is a 211cc making 4HP at 3600 RPM.

Remember that HP is a function of torque X RPM. Diesels generate lotsa torque, but only at low RPM's, if i recall because the flame front velocity is quite slow in diesel fuel. Of course, Audi now has a road race car that has been kickin butt, so there have been some obvious advances over the last few years, but i doubt they're using commercial pump diesel.

There is a group that is working on micro diesels now, but still don't see any products yet.


The Dixon Diesel site looks interesting, but i seriously doubt they are using pure diesel fuel either, exemplified by their selling thier own fuel and the statement "No need to be a home chemist".

Bottom line, unless major new developments have come along, you still need a rather large engine to make it worth your while if you want to run pump diesel.
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Small world. I worked at directorate of combat developments as the user representative for the Air Warrior operational requirements document. I did my fair amount of travelling to Fort Benning to TSM-Soldier and sat in on a lot of Land Warrior meetings. Power has alwasy been an issue :)

There are two types of model airplanes: GLOW and Diesel. Unfortunately, the "diesel" engines that are often modified with a Davis diesel head are not "pure" diesels and actually burn a mixture of ether, diesel, and lubricating oil.

There is no small diesel option at this time for a motorized bike. You may ask Davis Diesels and see if they can convert a 50cc gas model airplane engien such as a 3W or Desert Aviation engine for diesel use. The cost may be prohibitive.

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Imagine this engine on a bigger scale to suit MB and run on bio-diesal or whatever else works.
There is a 4-stroke version somewhere, the pushrods ( external) and
cam ( internal) are near the propellor shaft.

But don't these, if the radiator is inbuilt, it don't last


The first unit described is a diesel engine (compression ignition) but doesn't run on diesel pump gas : " was using kerosene(1/3), ether(1/3) and castor oil(1/3). ". You invariably need to add something that is more volatile and has a faster flame front (in this case ether) to support those kind of RPM's.

The other links show the tyopical size required (big) for a small HP engine running commercial diesel fuel.
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Small world. I worked at directorate of combat developments as the user representative for the Air Warrior operational requirements document. I did my fair amount of travelling to Fort Benning to TSM-Soldier and sat in on a lot of Land Warrior meetings. Power has alwasy been an issue :)


I too spent a fair amount of time at TSM-Soldier Benning... and, with the Dismounted Battle Lab, sloughing around in that **** Georgia red clay at 2AM and 20 deg F playing with Land Warrior and Objective Force Warrior hardware... some of that clay never washed out!

Small world indeed.