I recently had an odd Dooling 29 pass through my hands, although I did not realize it at the time. The purchaser pointed out that the exhaust was on the left hand side of the engine, whereas all the Dooling 29's he had seen (he has five others) have the exhaust on the right hand side. He says that the crankcase is not symmetrical and you can't just swap ends (as you can with, say, a K&B 4011). He wonders if this is a factory modification. Does anyone know if Dooling produced any 29's with the exhaust reversed?

Jim

There was a picture of one on here a couple years ago with left hand exhaust. We all thought that someone had swaped ends with the front and rear?

All the Doolings I ever saw had the exhaust on the right side.

Enjoy,

Jim

since the subject of swapping sides on the exhaust came up. I have the older irvine 40s, a Q40 (the Q40 SAME AS THE DIESEL)
except for the head, and the crankcase appears symmetrical would it work on these? just a rhetorical question since I do no have the need to do so
I think I just answered my own question the intake passage slot is lower in the crankcase than the exhaust just noticed this,not aware till I saw Bills answer

Jim and Jim:

The Dooling 29 engines all came from the factory with the exhaust on the left, when looking from the "Pilot's" position. I have no idea how or who started reversing the cases, and they do reverse just like the K&B 40 engines.

According to the Dooling brothers, the engine's pumping efficiency was better that way. Looking from the front, the mixture inside the crankcase was rotating ccw, and that tended to throw it directly into the circular bypass. With the exhaust on the other side the mixture with its ccw rotation, aided by the crank as well as the rear rotary valve, had to make a complete reversal of direction to enter the bypass port.

If you pull the rear cover you'll see a bypass port unlike 99% of the two stroke engines you've ever seen, and when I tried reversing one for r/h exhaust I lost a lot of rpm. Didn't want that loud exhaust pointing at me. I put it back to original.

The Dooling 61s were also delivered with the "Reversed" exhaust.

Bill.

Bill
Did you have that the right way round? With the exhaust on the "normal" side any swirling in the crankcase directs into the transfer ports. Every (photo) I've ever seen of a Dooling, both the 29 and 61, has the exhaust on the normal side. The parts diagram schematic shows it normal too. As for their transfer arrangement, I've often wondered why no other engine used it seeing it worked so very well with the Doolings. I'm still kicking myself for selling my 29

Any engine that has a removeable front and back end can be swapped to put the exhaust on the other side but there's a hidden trick. You have to turn the rod around as well.

Perhaps this will help:

http://members.coolcats.net.au/~scep...s/dooling.html


George

DU and George:

When the Dolings were flying in competition, I never saw one with the exhaust in the "Conventional" location.

Looking at Georges posted drawing you can see the round shape of the bypass. This was deliberate, having gentle curves for the mixture passage instead of the abrupt turn at the top of the port for entry to the cylinder. A comventional port comes straight into the crank case, and the circular flow of the mixture goes straight into it. The Dooling did not have this straight entry, the mixture had to flow sideways with more gentle turns into the port, and then into the cylinder.

In all honesty, I never saw a Dooling with a r/h exhaust until I saw them on RCU.

Bill.

PS: Seeing the $23.95 price for the complete engine brand new... wr.

I've heard from the guy and he agrees that the front and back can be swapped so no mystery after all.

Incidentally the Madewell 49 has the gas transfer going through the piston like the Dooling 29.
Jim

Jim:

The ports in the piston skirt are very common. The McCoy 60, and the later ringed K&B engines are jut two that have them. In most the ported piston skirt was merely additional transfer area, but in the Dooling design it was the primary porting.

Bill.

LOL...thanks George, I'd forgotten I put that on a web page for future reference

Bill..agreed that a lot of engines used ports in the piston (all the old OS Max's had them) but in the Doolings (and Madewell as Jim pointed out) it was the only transfer method. I remember seeing photos of the Carter Dooling where one of their hop up mods was to file the round ports into rectangular slots in the piston and liner. It seems to me that if ALL the mixture has to pass through the piston skirt then it should help keep both the piston crown and the wrist pin area much cooler.

But whichever way it was assembled, in my eyes the Dooling 29 was and still is the best looking model engine ever made, even better than its big brother.

Didn't we do this about 2 years ago. I bought my Dooling 29 new in the box from a hobby shop many, many ,many years ago. Right or wrong it came with the exhaust on the right looking at it from the pilots position. As did my 60.

Denis

In all honesty, I forgot who had posted it. I had printed a copy and it had the web address on it.

I agree...and it was the first I saw that had such close tolerances that it was assembled without gaskets.

On the porting, also consider the contoured baffle on the piston. My guess is that it was designed to cool "Hell's kitchen".

My Dooling .29 is in a box in pieces. It needs the prop stud (which I can make from a bolt), a set of rings, and a needle valve. I'll try a K&B and a ST needle to see if it will fit. Not an urgent project...but I have a "Royal Rodent" kit to put it in whenever...

George

George:

The Dooling and McCoy needles had the same thread, the Super Tigre thread was different. The K&B "Block" carb needle also has the same thread as the Dooling/McCoy. Except for the ST, they will all interchange.

McCoy needles were blued, and were more brittle than the Dooling, if you hooked the McCoy needle on something it would break, the plain steel Dooling needle would bend, and could be straightened. Most McCoy needles were replaced with the Dooling for that reason. I still have some NIB Dooling needles, but as I said, you can get the K&B needle from MECoA, I can't tell the K&B from the Dooling.

There have been several posts about a gentleman who will make rings for any engine, don't remember his name.

What's your next excuse for not flying the Royal Rodent?

Haw.

Bill.

Perhaps that was Frank Bowman on the rings. Never dealt with him but he has an extremely good rep.

Both the Dooling and the Royal Rodent were given to me by a friend (at different times). The pan on the Rodent has the LG installed and mounting holes drilled. The rest of the RR is in the kit box.
When I got the Dooling parts paper out of the engine box I noticed that the sides of the mounting lugs have the same paint color as the RR pan. Ah..Ha.., now I know what engine the pan is drilled for.

Actually, the Dooling and the RR are a bit down on the priority list...but someday...

George

George:

That's affirmative on Frank Bowman.

Bill.

Been down the road with the Dooling's ,Mc COY's & several dozen other engines with different ideas on porting , exhaust location & induction but I have yet to see any engines stranger inside than the ATOM .09 , with it's port inside the top of the piston or the Thunderbird .65 with a built in supercharger impeller . Both good engines for 50 years ago . MAX H.

Max:

The first application of an internal piston port that I know of is the WW I Gnome "Monosoupape" (single valve) rotary engine. The inlet valve was part of the oiston, only the exhaust valve was visible. Looked like it really had only the one valve.

Bill.

Bill , Guess I should have said a piston in a piston which the Atom has. The early Gnome had a set up like you said but the later ones were inducted through holes in the cylinder wall "Like the Brown & O&R Engines") & that's when they started calling it the "Monosoupape" which your right means single valve . MAX H.