A question here for those in the know. I've got a 1970s version of the Babe Bee glow head motor and am considering a conversion to diesel. I hope to gain a bit more run time with the same power level.

I've already got a good contra piston head from another motor on hand, so would only need to spring for the beefier crank shaft.  I like diesel motors.

Worth the cost and effort, or should I leave well enough alone and stay with glow?

Dave Mo...

          I have used the stock crank and it's very short lived. My first example, it lasted 2 flights. You need the heavier crank. It was neat but hard to really get back to back settings. If you like diesels and tinkering, they're fun to play with.

If you have a Baby Bee and are happy with the performance but just need more run time why not switch to a 8cc tank such as used on the Black Widow, Golden Bee, and Texaco? That is 60% more capacity for a known-good combination.

If you want to fiddle with it to learn which settings are "hard" and break cranks, bend rods, etc. then.....

My best luck with a diesel-ified Cox was using a Cox car crank and case that has the larger journal. I had to make a special adapter for a prop drive. I believe I used a MECOA head which Larry loaned me. Thanks, Larry!

Dave

There are also Car Cox Engine cranks that adapt easy to propeller with the correct adapter on the nose...

while I do love my dinky and very cool cox engines...there are a whole lot of small diesels to play with

jest sayin

Agreed the stock crank won’t survive. The Davis Diesel crank and head are a viable combination. High ether fuel will reduce the required compression and prolong life.

My advice is buy a PAW diesel from Dr. Diesel and live happily ever after.

Hi All, I must agree with Larry here,  I've done the diesel head conversion with reed valve engines;
but, all you end up with is an engine that has about the same kind of power as a stock glow reed
valve engine that can swing a 6x3 prop. I have messed about with PAW .8cc engines from the early non
anodized muffs to the latest SBR and TBR .8cc diesels.  The Paw SBR and TBR engines produce
much more usable sport and stunt performance than ANY TD engine. A TD simply cannot swing a
6x4 as the PAW engines can. Barry Baxter has powered 250sq" models with a TBR and I've flown
several Ringmaster Jr models(nose moment and fuselages modified for diesel flight) using a
plain bearing and an SBR .049 diesel. My Ring Jr's fly on 44' x .008" lines, are full pattern capable
using a Cox grey 6x4 prop and can complete a stunt pattern using only 1/2oz of fuel. 

In addition, the PAW .5cc diesel is a jewel that can pull a scaled down 160sq" PDQ Lion Tamer
on 35' x .012" (old 1/2a Combat lines); also flying the complete stunt pattern.  Bare used a 6x3
prop....that resulted in screwing him into the ground.

Sadly the prices for Paw .049s has increased considerably;  but get one if you can.
Tony G.

The only way to get diesel fuel stains out of your clothes is with scissors. But they will still stink up the house.

I think the concept is marvelous, the performance, properly run, is amazing, and I am still going electric.

I did an article for RCM titled “Who Has the Beef” comparing an OS FP with glow and diesel heads. Except for the most unreasonably small prop, the Davis head outran the stock head even using 15% Nitro fuel.

Blew me away!

Side note, the testing was done at a local park. A kid came over as I was working to find the latest new starting setting (it is different for each prop) and said “Can you take it back?” I intellengently replied “Huh?” He said “Well it doesn’t work.”

To quote WCFields “Scram, kid ya boddering me!”

Motorman:

It's nice to be reminded of basic physics every once in a while, i.e., the ol' surface area-to-volume ratio haunts not only small winter birds, but our little motors as well. Very good reminder!

I've had good luck with a 2.5 cc KMD diesel motor from Russia, so am familiar with the ether tussle. 'Round these parts, the JD ether sells for $4 a can; tolerable enough.

Nice (and likely very useful) metaphors describing the two engines. Will keep them in mind as this progresses.

Thanks!

Dave Mo...