Ok guys its on the bench ready to go will fire up tomorrow fitted as I said before with a PAW needle valve assembly prelims look good look nice draw of fuel on choking
no leaks head or back plate martin

It is looking good. Do let us know how it goes,

Sadly a no go on DAVIS ABC mix compression is low will mix up some 70% ether/30% oil no kero and give it a try

Martin,

I don't believe kerosene was ever added to the fuel for a Drone.  When I blended fuel I believe I used three  quarts of either to one quart of caster oil.

Chris

Dronefuel

Drone fuel did not work last try. Jack

SAE # 20 mineral seems a light grade of oil for the application. On further thought, probably pretty near the viscosity of medicinal castor oil, BP spec.

I as thinking of 20W30 automotive oil which I have and of course Castor oil will do the 70/30 mix any thoughts on which guys????
Wonder why Drone did not say castor oil in their mix martin

Interesting to note that SAE 30 oil was used for break-in and the compression ratios were sometimes 20:1.
And the oil % effected the comp ratio.

http://modelenginenews.org/ad/drone.html

Makes sense would not get by the piston as quickly,being thicker, better seal between piston and liner thus hold compression martin

Hi Martin,
I think that the higher the oil content the less the compressibilty of the fuel air mix, and its this effect that raises the final amount of pressure in the cylinder.

The seal, well a high oil could help in a worn engine.

Cheers.

Martin,
I was told that the additives in automotive oil ( such as antifoming and detergents) would inhibit operation in a Drone. Thats why I used casteroil.  I used   

Using the original formula of 75% ether to 25% oil was done way back before they had fancy additives in the oil. But the mineral oil was important for moderating the harsh combustion effects of all of that ether too.

Using a normal model diesel engine fuel formula should work OK though. I have been using Davis Diesel fuel to good effect in mine. I could probably get a little more power with the original mix formula though. But if the compression is low, it may not work.

You might need to go with a heavier grade of oil to help seal up the piston to cylinder better.

Yes, ether tends to detonate rather than combust and mineral oil dampens this, castor oil doesn't seems to.

http://modelenginenews.org/faq/fc_diesel_ops.html

Made up the 70/30 drone mix and still a no go a few pops quite a puzzle, compression seems ok, new PAW needle assembly, just for kicks pulled the liners on the two cylinders i had
( piston to liner wear bad compression we tried them. just as an interest pix here they are large port of course exhaust small one (only one 180degrees from exhaust)
is small and directly in line with top of bypass bulge on cylinder casting but it works well you would think not a good breather but it is martin


toying with the idea of having them chromed

I am concerned that you may not have Drone cylinder sleeves there. I do not remember mine having a lip on the top of the sleeve.
Mine all are simple straight cut cylinder sleeves with no lip on the top. There is a shoulder down inside that the cylinder sleeve butts up against, so it doesn't need a lip. But maybe its my memory mixing things up. Here is a pic of one of mine, Granted this is the BB version. I'll have to look to see if I have a pic of the bushed version someplace too.
The bushed version may not have the shoulder on the crankcase for it. I don't remember now.

Earl I very well have the wrong sleeves which would explain no charge entering the cylinder intake port will not line up right thx martin

mine is bushed not BB also only 1 head have 3 crankcases assembled engine from parts #7523 other 2 cases 2951 and 1399 stamped on them

I looked through my pics but I didn't take a pic of a bushed Drone engine cylinder sleeve. But the pics I did have show a lip on the top of the cylinder so you are Ok in that respect. yeah it is easy to get the cylinder sleeve in wrong. Also the piston as well. There is a cutout or notch in the piston that corresponds to the transfer port. The bottom of the piston skirt matches the intake port on the back. I had to think about it a while to be sure.

On mine I had to close the needle valve up, then get the engine to run off the prime for a second, then slowly open up the needle valve. it seemed to be quite sensitive at first. But once I got it in the ball park and the engine would run, it turned out to be OK then. The needle holder has basically a brass tube and no shoulder or step inside, so the needle would block the spray bar hole off and the taper would gradually open the hole up. Sort of in reverse of what we normally see nowadays where the needle butts up against a step of seat.

EARLE Perfect line up on liner in cylinder piston step 180 degrees around from exhaust and yes the lip on liner fits recess in cylinder. The compression still might be too low for a fire off, this piston/liner best of the lot others almost no compression, lots of wear martin
We did use the 70/30 mix not a poptried a few drops in the MPJET 061 2 flips and screamed like a banshee

will have to scout around for a decent piston and liner

As a last resort Martin, perhaps the piston could be "cherry bombed" to see if it will "grow".

I have copied this extract from an article concerning building a replica taplin twin prototype published in model engine news. The author is not named.

"... George Aldrich knows a LOT about speed engines and tells me he "grows" cast iron pistons a couple of thou by heating to red heat and oil quenching. On the theory that this pair was stuffed anyway, I gave it a try on the worst one (the front). "Before" measurements gave a diameter of 0.5044". The piston, held on a piece of soft iron wire was brought at a bright orange in a propane tourch and quenched in chain saw oil. The "After" dimension measured 0.5060" with no appreciable out of roundness. A little honing soon removed the scale and produced a good fit in the front cylinder. The piston is still not as polished as I'd like indicating just how under size I'd turned it (and how blunt the tool had been). Reassembled, the front pot would now "pop" on a prime. With this encouragement, the back piston got the same treatment with similar results: growth of 0.0016" and no distortion. Simply amazing. With both pots a-poppin, I just had to try for a run."

Fiery will have to give it a shot have 2 p/l assemblies plus the one on the engine thus three martin

Martin;  I don't remember ever taking the sleeves out of any of my engines,  As I understanding it, the last Drown that I sent you, popped and sounded like a AK47.  If it would run on the prime then I suspect that there is something wrong with the needle valve assembly, You state that when you choke it it draws fuel well so I'm not sure what the problem is.  You may remember the Yellow WWI biplane that I built but never flew was if I remember correctly, was susposed to use that last Drone.  That was the last engine, that I used in my Secret Weapon but after the R/C meet in Summit, NJ, where a competitor "accidently" stepped on the wing. I stopped flying after that. I repaired the plane but it was never the same.  This was about the time we discovered girls and cars  Chris

Chris I did the grow the piston stunt by heating with a torch on one of worn piston/liners we did get a better compression came up we did get a couple of short fires and yes loud
will have to see if we can get a run fuel 70./30 drone mix used also fired on the davis premade fuel which is the 32-33 %?? on ether plus kero and oil of course ,will try the electric drill thing
run for a couple of minutes oil only to limber up will loosen head A tiny bit to kill compression to grt a good spin martin

well guys Swapped every piston/liner combo . a no go, made up a tiny amount of fuel and dyed it bright red to check for leaks around head and back plate not a trace, flat out low compression, will scout around and see if we can come up p/l s. on removing head the cutaway in top of piston perfect alignment with passage slot in liner martin

Just for kicks tossed my NIB PAWBR 29 on the bench tank not hooked up a little fuel DAVIS ABC down the venturi about 10 flips and got kickbacks finally after backing of the tommy in steps to one full turn open from where it was off it went total time from box to bench to run about 5 minutes martin
10x7 why ? first prop I grabbed