Dieselising a Bee - Be warned!

ian1954 Sun May 26, 2013 11:19 am

I have a few dieselised Cox engines but decided to make my own rather than use an "add on" .

So lathe ready and soon - aluminium head, steel liner and a steel contra piston later (the gnarling on the fins was caused by my mole wrench! The leather strap I use persihed while applying pressure!)

Minor adjustments and ready for flicking!

I was very pleased - wouldn't make it the same way again and I have more ideas. While it would appear to run fine and compression was easy to adjust, the fuelling left a lot to be desired. It ran far too rich and I think the venturi need restricting. It shouldn't have used so much fuel so quickly.

I ran about 8 tanks of fuel through it - topping up on the fly - and then .............

I was aware that the standard Bee crankshaft was weak but not that weak! I am not sure how they are made (and my pictures aren't good enough) but the broken cross section looks "grainy".

Oh dear, how sad, well never mind! More fiddling in order but I am quite high on diesel fuel at the moment! Better not power up the lathe!

**Admin** Sun May 26, 2013 12:30 pm

Yep, those diesels run hard. time to move to a car crank and case, DDD crank or one of Matt n' Bernie's killer cranks.

It almost looks like you were using a early thin web crank which could be why it gave way easier than you thought.

Post 1959 shaft (they are even thinner in a '56!)

Post 1986 shaft

Post 1959 on top, Post 1986 on bottom

Post 1959 on top and post 1986 on bottom

Surfer_kris Sun May 26, 2013 12:38 pm

You need the "car" crank in order for them to hold up to the higher compression ratio. Davis Diesel sells kits where you get both a diesel head and a suitable crank.

Cox International Wed May 29, 2013 12:13 pm

The problem with the standard crank is that they are hardened too much, effectively making them brittle.

Our diesel cranks are "Killer Bee" style but, for the hardening, we deviated from OEM specs and made them softer.

A diesel crank and diesel head conversion kit we retail for $27.90 in total.

http://coxengines.ca/cox-.049-killer-bee-diesel-crank.html

http://coxengines.ca/diesel-head-conversion-for-cox-049.html

and $2 more for the red version:

http://coxengines.ca/diesel-head-conversion-for-cox-049-red.html

bullit132 Thu May 30, 2013 1:25 pm

what type of fuel do you use for a set up like that??regular diesel from a pump,or some kind of special blend,i think i might like to mess with that if the fuel isnt hard to get..

Cox International Thu May 30, 2013 1:47 pm

Special fuel. Here are links to some fuel guides:

http://coxengines.ca/files/FG.pdf

http://coxengines.ca/files/DFD.pdf

ian1954 Thu May 30, 2013 2:51 pm

Diesel fuel for model engines can be the subject of great debate.

For engines over 1cc, I have always followed Progress Aero Works recommendations:-

Castor Oil, Paraffin, Ether, Iso Propyl Nitrate or similar

Running in ----------------- 30%, 35%, 33%, 2%
Fully run in ----------------- 25%, 40%, 33%, 2%
Fully run in
- BR Models ---------------- 20%, 48%, 30%, 2%
Fully run in
- TBR only
(Racing and Speed) -------- 15%, 50%, 32-33%, 2-3%

0.5 - 1cc I would increase ether to 35%

sub 0.5cc I would start at 40% ether

kevbo Fri May 31, 2013 4:56 pm

Just a note: Paraffin(UK English) = Kerosene(Yankee Speak)

ian1954 Sun Jun 02, 2013 2:43 pm

I am awash with "diesel stuff" and was just trying to warn anyone who converted what would (not might!) happen if attention wasn't paid to changing the crankshaft in a bee. It was another experiment of mine.

I wouldn't dare fire up the Pee Wee. Will probably transfer the head to a Tee Dee.

I still have lots to play with (apart from my own constructions!)

Surfer_kris Sun Jun 02, 2013 4:00 pm

The PeeWee runs fine as a diesel. Just use a large enough prop (6x3) to keep the revs and compression down;

ian1954 Sun Jun 02, 2013 4:04 pm

That is good to know. I would not have risked it without knowing.

colibriguitars Sat Jan 06, 2018 10:56 pm

Hi Ian!

Happy new year!!

well, i been playing with my two cox conversions... i been reading a lot, and mostly all comments are: cox are not suitable for diesel.... the crank is to fragile....

i get 2 diesel heads from hobbyking as Cox International is not shipping to Mexico. and i ordered just one diesel crank. so i decided to make my tries with bought.

after 12-20 runs with stock crank, my engine still going. even the teflon disk is in good working order. I even start my babyDieselBee at same time as my MP jet.... they work very similar, the cox needs maybe 6 more flips to start that my MP, but they can run as low revs... what is i´m looking for..... love FF models (sport) and regular cox, even with 10 nitro and bigger prop can be to powerful for some models...

about dieselized pee wee..... well, my head DDD is well made, but maybe bad calculated, as even at lower compression settings is to hi, and i broke a crank..... so i sanded a little the contrapiston and will give a try soon.

Here a couple videos of my cox
https://www.youtube.com/watch?v=ceIPdA9-JNo

https://www.youtube.com/watch?v=s9mgwBEuVqo

https://www.youtube.com/watch?v=F0tjD4CwcA0

https://www.youtube.com/watch?v=0yAX1zGN9B0

MiniatureAircraftFactory Sat Jan 06, 2018 11:31 pm

I messed round with making myself some diesel cox heads in the late 80s, the 049s seemed ok i never broke a crank on the 049s.... but... the peewee...the crankweb scapped as i was flicking it on the first little pop from the engine, I fitted a new crankshaft....( had spares then ) and the new crank snapped first flick again so I changed again....and made a bit of wood to add a dome shape to the aluminium drink can i was using as a compresion disk, tried again and it runs fine now still on diesel
For fuel originaly i used commercial fuels but often now I just use equal parts by volue of diethyl ether ,car pump diesel and castor oil, sometimes with a few ml of mekp ( fiberglass peroxide catylist) added per litre of fuel but usualy just the 3 main components

Oldenginerod Sun Jan 07, 2018 5:34 am

MiniatureAircraftFactory wrote:I messed round with making myself some diesel cox heads in the late 80s, the 049s seemed ok i never broke a crank on the 049s.... but... the peewee...the crankweb scapped as i was flicking it on the first little pop from the engine, I fitted a new crankshaft....( had spares then ) and the new crank snapped first flick again so I changed again....and made a bit of wood to add a dome shape to the aluminium drink can i was using as a compresion disk, tried again and it runs fine now still on diesel
For fuel originaly i used commercial fuels but often now I just use equal parts by volue of diethyl ether ,car pump diesel and castor oil, sometimes with a few ml of mekp ( fiberglass peroxide catylist) added per litre of fuel but usualy just the 3 main components

I'm surprised that the car pump diesel works ok. Normally you need to use kerosene/paraffin.

MiniatureAircraftFactory Sun Jan 07, 2018 5:39 am

Car diesel is better in some ways as it contains the anti knock additives, My original fuel i mixed used runny bbq lighting fluid, red diesef for heating also works fine

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