Dieselised Cox 049 (Part I) Using Davis Conversion Head

Converting a Surestart Cox 049 to diesel using a Davis Diesel Development (DDD) conversion head. I did not bother with changing the crankshaft to the beefed up version but it seemed to be all right, well, so far so good. Bought those heads years ago but no time to play with them; busy trying to make a living and bring up a family. Well the same old story! Thank you for watching.

[@umbongonights]

Although this video is almost six years old, KZbin has decided that I might be interested …. And it was right!! I bought two of these or at least similar products ..perhaps twenty or so years ago. I fitted one and almost immediately and predictably broke the crank shaft! Incredibly I found the other conversion kit a few weeks ago and this video has inspired me to give this another (more careful) go. Thanks for posting so many years ago .. I hope those years have been kind!

[@mylittlediesels]

Thank you, those years have been kind to me and I'm still playing with my little diesel engines.

[@charlesflint9048]

I had great fun in the 60s with the .049 engines. I thought the .020 were wonderful; so small and easy to fit. These Diesel engine conversions look great, it’s all coming back! I’m going to look into this now.

[@mylittlediesels]

Good on you Charles! I too had great fun in the 60s with model engines and the Golden Bee was my first one. I chose it instead of the Babe Bee because it has the stunt vent fuel tank. Oh yes , the .020 are cute but the tiny .010 are objects of desire.

[@scotthaddad563]

Great!, I purchased one of those conversion kits in the seventies. I’m not sure of the maker bud it worked by adjusting the compression with a screw such as you have there, the screw moved a piston inside the head against a teflon disc. Mine kept bursting the discs after only a few runs . I returned it to the hobby store and picked up an OS Max 10 with Schnerle porting instead which I converted from C/L to R/C with throttle.

[@jeremyburton9038]

Yes they are a lot of fun . I have a big collection of them and I enjoy running them

[@mylittlediesels]

Great! Most aero-modellers started with a Cox 049, likely a Babe as only a lucky few could afford a TeeDee.

[@valic000]

Nice informative video! Thumbs up for that. As you read for sure,I broke some shafts on my old cox.They already broke when fire up the first stroke,not in the run.So the deharded shaft hold so far. I am sure,the HD shaft work excellent,if put in real service with a model. But I agree what you say..a must for a diesel head! And they run pretty well,low weight,so great for free flight or a small CL model. Thumbs up!! :-D

[@mylittlediesels]

Hi Peter, thanks! I too broke the shaft fairly early but looking at those aluminium discs (yes, I still have them!) the metal from beer cans in the 70s is quite thick compared to nowaday's one. I am pondering if I should conduct another trial using thiner metal sheet for the disc and sand away some material from the Cox glow plug so that the dome shape is shallower. Peter, have you thought about modifying a Cox glow head to a diesel head with a variable compression lever?

[@valic000]

Making a real contra piston will be the best.I never try to use / convert a old glow head.But I have a Davis diesel head for a 0.9 CU medallion and that looks great. It have a alu contra piston,in the alu head. Its anodized blue with a L shape lever. I think they are still for sale at Davis Diesel development. The Teflon disc works,but dont hold on a long time..

[@mylittlediesels]

That's interesting. I am sure I have read somewhere that Bob Davis had only made a dozen or so of the .09 heads for TDs. so yours could be very rare. Apparently they break if pushed too hard. However, the medallion, being a "poor man's TD" has just a drilled circular intake valve port as opposed to the rectagular one on the TD crankshaft. So theoretically, the medallion shaft is stronger so might not break so easily.

[@davidmccumber8805]

There’s some videos on here where people are using gasoline and two-stroke mix oil I think 25:1 ratio And a gasoline glow plug they say and I didn’t even know they made ‘em.

[@chrischannon2739]

Brilliant, thank you

[@colibriguitars]

Hello my Friend!!!! hope you are doing Well and having fun!!! just finished my first Diesel head made in my mini lathe! seems to be a good runner. you create a monster with those cox dieselized! Cheers my Friend!

[@mylittlediesels]

Well done my friend!! Could you show us and how did you cut the threads?

[@colibriguitars]

Hello again! well, sorry for not sharing the process, but was very focused. i will make 4 next couple weeks, and will make some videos, For me, all this is new, never before done boring or threats... is not hard, but needs to be done slow and measure every pass. My lathe has gears, so i can change them to get the threats i want. not easy and sharpening the tools for that small threats are hard. but is a very good way to spend 6 hrs on a project. cheers my friend, and hope to share some videos soon!

[@mylittlediesels]

Thank you. Looking foreward to watching that.

[@lovetofly32]

This was painful to watch. Everytime he would tighten the one on the head it would just start to run better and then he would back it off and itd continue to run slower and crappier..

[@davelowets]

It's called "breaking it in rich, and on low compression"...

[@Lozzie74]

I agree. I kept thinking “lean it and compress it!”

[@ashj_2088]

Thanks bro my pop used to mill them. He's long passed an i couldn't find out what they ran on ,coz they had screws instead of glow plugs .thanks again

[@mylittlediesels]

Yeah you are right, they have screws instead of glow plugs. They are compression ignition engines and loosely called "diesel" engines. The screw is to change the compression ratio. The fuel is a mixture of paraffin, castor oil and ether and the very basic one has equal portion of each i.e. 1:1:1 ratio. Commercially available model diesel fuels have a little bit of amyl nitrate or isopropyl nitrate added as ingition improver; for home brew one can use cetane improver. Hope that helps.

[@christophertibbetts2458]

The diesel engine works because the fuel has such a low temp burn rate. The compression of the engine itself ignites the fuel.

[@keithjurena9319]

The diesel fuel used has a very low auto ignition temperature due to the ether and some nitrate esters..glow fuel uses methanol with nitromethane to lower the auto ignition point..methanol has a very high auto ignition point. But in comparison, glow plug/head nichrome filaments get awfully hot when energized which greatly helps starting. Once running, the highly stratified mixture burns hottest at the filament, coolest at the piston. Likewise, diesels ignite at the top by the counter piston but only the hot air..the ether and kerosene cool the piston..run either lean and these engines seize.

[@jackbn9353]

The problem with Davis diesels is that teflon disk. The disk severely reduces cooling through the head.

[@charlesbovalis6591]

Awesome - what size prop are you using ? Also - what is your fuel blend ratios used ?

[@mylittlediesels]

Hi, thanks. It was a Thimble Drome 6X3. Fuel was Model Technics D1000 (available in UK only?), which is ether 35% kerosene 35% castor oil 28% and isopropyl nitrate 2%.

[@mrslopez137]

How does this work without using a glo plug? The original cox motor uses a glo plug and a battery to start it but I don’t see it on this diesel conversion.

[@mylittlediesels]

Hi, thank you for your interest on model "diesel" engines. I am not very good in explaining things but I shall try. They are compression ignition engines and use model diesel fuel containing ether, gasoline and castor oil (some with ignition improver added). The ether has a low flash point and will self-ignite when the air/fuel mixture in the cylinder is compressed by the piston (the temperature of air increases when compressed). This is the reason they do not need a glo plug.

[@rogertycholiz2218]

@@mylittlediesels Not so! There is NO gasoline in the fuel mixture. The mix is Kerosene {diesel fuel} and SAE 40 engine oil and a little ether. Modern truck diesel engines compress kerosene only. It has to burn-not explode like gasoline engines. Gasoline explodes in the combustion head.

[@michaelnelson9140]

@@rogertycholiz2218 not true! Both gas and diesel burn under high compression and heat. If they exploded, that would be a violent action, and would destroy the piston and cylander. Seems like a lot of people get this wrong.

[@charlesbovalis6591]

I totally agree on your video comment - all diesel lovers should own a Cox diesel - indeed ... I plan to purchase one soon. One final question: Cox recommends to first break in the engine with conventional cox glow fuel - did you do that or you just jumped right away into running it with diesel fuel ?

[@mylittlediesels]

You are correct, it's mentioned in the instructions to break-in as a glow first to free up the moving parts but I didn't folllow it. I also didn't change the crankshaft to a beefed-up one either and it seemed OK as I didn't stress it too much.

[@charlesbovalis6591]

@@mylittlediesels Good to know that even without changing the crankshaft the engine did not give up ... well if you run it on a slightly decompressed mode and a bit rich you have nothing to worry for a very long time. I am gearing up to purchase a brand new diesel-converted Cox 049. I will still go through a few tanks of cox-glow fuel to losen things a bit and then straight to diesel mode. It will be lots of fun. I plan to put that engine on a brand new "vintage" model for two channel from BMJR - the Bombshell Buzzard, wingspan of 44" and designed for a Cox .049 engine ... ohhh I can't imagine how great it will run with a diesel Cox ... Can't wait ..

[@xzqzq]

I am curious about the Davis diesel head for .049 Cox, wonder how well they work. Obtaining glow fuel difficult where I live, but the components for model diesel available...plus Cox engines on E Bay are very inexpensive... even if I break a few, just reuse the diesel head and HD shaft on the next engine... are you not supposed to use the motor-driven starter on diesels ? Thanks

[@mylittlediesels]

Hi, I have two and I have no issues with them. I have only blown one disc so far. Yes, most people would agree it is saver not to use a starter on diesels as you might break something.

[@calescapee9642]

I've got a diesel McCoy 049

[@mylittlediesels]

Lucky you! Is it radial mount or beam mount?

[@thebug4046]

i have tried and tried and never been able to get mine to run so i gave up and put the glow head back on it

[@mylittlediesels]

Sorry to hear that. Did you check you had seated the disc properly and check for leak? Did you get the "diesel pop" when you flicked the propeller? Throw your glow head away and put yopur diesel head back on, quick!

[@thebug4046]

mylittlediesels everything I'm using is brand-new and the only time I've ever been able to get it to pop or Kik or do anything is if I go with a 7030 mixture of ether and castor oil any other mixture I try nothing happens I am actually making a video about it you can see that on my channel within an hour

[@mylittlediesels]

just saw it and replied.

[@haydenbutcher73]

t 404

[@davidmccumber8805]

Are you using just plain ole diesel fuel or mixing it with something else for lubrication or something?

[@mylittlediesels]

It's not diesel fuel at all! It's a mixture of ether, paraffin and castor oil; some model diesel fuels have an ignition improver added. It's called diesel because the ignition process resembles diesel engines, which is compression ignition.

[@colibriguitars]

Hi Again!!! what prop size are you using? Thanks for sharing!!!

[@mylittlediesels]

Hello! I used a Thimble Drome 6x3 which seemed to be a good choice for this Surestart. I had not done a short run with nitro duel to loosen it up as recommended by DDD. As with my usual practice I started with exhaust prime first before filling the tank. Once I found the correct compression setting I got several short bursts of life and I knew it was getting there. Incidentally, I am making another clip on a Babe Bee (assembled from spare parts) with the beefed up crankshaft installed. The Thimble Drome 6x3 just did not work; all I got were kick-backs and cuts on my fingers! I managed to get it running on a Super Nylon 7x3 and it ran extremely happily on slow idling speed but laboured on faster speed. I changed to a Keil Kraft 6x4 and it just liked this one for the whole speed range. What I am trying to say is as all diesel lovers know, each engine is different as if they have a soul, you just have to find the right combination. Thanks for you interest. Regards.

[@edgarluisfernandespinto9962]

Did you replace only the head? Not the crankshaft

[@mylittlediesels]

Yes, I didn't change the beefed up crank shaft that came with the head. That sure-start cox was brand new so I knew I wasn't going to run it at top speed.

[@edgarluisfernandespinto9962]

@@mylittlediesels Thanks Friend!!!

[@edgarluisfernandespinto9962]

Can you send me your email adress?

[@gabrielhuang2343]

What is your fuel blend percentage？

[@mylittlediesels]

I used Model Technics D1000 which is Ether 35%, Kerosene 35%, Castor oil 28% and Isopropyl Nitrate 2%.

[@gabrielhuang2343]

@@mylittlediesels Thank you I will try it.

[@mylittlediesels]

@@gabrielhuang2343 You are welcome. The basic home brew model diesel fuel is equal parts of Ether, Kerosene and Castor oil. The Isopropyl Nitrate is just the additive to improve ignition, similar to the Nitromethane you use in your glow fuel. If you cannot get Isopropyl Nitrate in your country you can try using Cetane Booster for diesel.

[@mikew3232]

Harden Associates was Roy Lever, then 'Powermax' Millet St Bury.

[@mylittlediesels]

Thank you for the info.

[@johnslugger]

*Not a lot of power on Diesel. Nitro runs about 20,000 RPM higher.*

[@colibriguitars]

Hi Again! i just get my heads and run my baby bee today! using British formula....1/3 each. hard to start, need to be almost flood, and once started, unscrew compression and close needle. but runs. i just upload a video. hope you like it. Thanks for alls support! please tell me what you think. Best Regards Rodrigo!

[@colibriguitars]

ahhh, forgot to mention that i reset the piston before assambling, so the engine is like new and in very well condition. sometimes get to hot and stops if get hi revs. (i used a 7x4 prop)ç

[@mylittlediesels]

HI, great news! I will have a look and sure it will be good.

[@tomrisar5492]

This engine must use a different fuel than the COX glow plug engine fuel.

[@paulweezy138]

Tom Risar you mix in some castor oil and ether.

[@tonypinto9952]

This engine is sputtering and not running at full rpm turn the head screw clockwise and the rpm will increase

[@mylittlediesels]

Thank you for the advice but I like the sound of slow ticking over speed. In fact sometimes it's a challenge to see how slow I can get without stopping. The truth is I am worried my neighbours might complain about the noise :-)

[@rogertycholiz2218]

Tony: I was getting really frustrated looking at his messing with the compression screw. As you and I know you have to screw it down until it stops sputtering. After that you work on the needle. I am surprised he didn't snap the crank!

[@lovetofly32]

@@rogertycholiz2218 oh my gosh Im not the only one! I was shouting "turn the damn thing in clockwise!!"😲 The smoother the better on the crank!!

[@Draxindustries1]

I had a KielKraft silver hurricane control line with the Cox 049. Wish I still had it..

[@mylittlediesels]

I also had a KK Hurrican but with a Wen-Mac 049 and I also wish I still had it!

[@rayswann7618]

the engine was wen mac not cox

[@Draxindustries1]

@mylittlediesels They didn't stay silver for long though did they. Glow fuel just took the finish off. I think it ran on Nitrex 15??