Pelle Gris

Hi Guys...

I recently bought a secondhand 20 year old 1:3 scale Toni Clark Pitts S1 equipped with an old Q35, and the old "U" shaped tuned pipe. I flew it today with the supplied MenzS 20x8 but the power seemed marginal, and the engine was very hard to tune. I managed to get the prop up to about 69-7100rpm. Flying had to be done at full power, as the engine was also very "perky", with a distinct point where the pipe "came on".
Are there any simple/cheap ways to get a few more rpmĀ“s out of the engine? I have a carb from a G-62 lying around. Would that help boost the power?

Eventually I plan on putting a bigger engine in the Pitts, as I would like it to carry a smoke system, but at 8,3kg (18,3lb) I donĀ“t think the Q35 can manage more weight.

Also what would be the best prop on this combination?

tkg

My Feedback: (1)

Simple, almost cheap hop up is a Q41. It will bolt right in, turns about the same RPM with a muffler so a pipe would add more.

davewallace

My Feedback: (29)

Hi Tinus,
A larger carb would give more power, but I think the G62 carb is a little big. A Walbro carb off a Sachs or Husqavarna saw between 45 and 52cc would work fine. 13.49mm venturi. They used to have a 41cc cylinder and piston upgrade available for the Q35 a few years ago. You may be able to get a good used Q41 or Q42 cheap. As tkg said, it would drop right in. Checkout B&B Specialties web site.

Dave

Westbender

My Feedback: (1)

I converted a US41 to electronic ignition and that thing really runs great! I believe the Quadra and US engines are similar. Does your Quadra have the magneto ignition? If so, go electronic and lose the weight. With a synco-spark type unit, you can time the full throttle advance to around 28 degrees to get some good power out of it. I believe that's where I have mine set. For the muffler, I bought a Bennet-Built (B&B) with smoke taps and it works perfectly. I even haul around the extra battery, tank (smoke oil) and pump and can still go vertical all I want. The orange and yellow plane in the picture is the one with the US41 on it.

Antique

My Feedback: (4)

The G62 carb is too big and the pulse hole will not line up....

the Wasp

My Feedback: (1)

what about the G45 carb ??

Jim

Antique

My Feedback: (4)

Same carb, HDA48D....
Years ago I tried 3 different carbs on a US41..
Bore sizes from 3/8 to 1/2, very little difference in rpm...If a larger carb would work they would come with one...
Some say a WA144 from a Q50 or 52will increase rpm, don't know for sure...

Tipover

My Feedback: (44)

I'd try a 18-6 prop. The old Q35's seem to like running in a higher power band. I fly a 22 lb, 1/4 scale Cessna 180 with this setup. Verticals really suffer with a 20-8.

Kevin

Pelle Gris

Thanks for your suggestions.

I will see if I can find some other props to try out. Unfortunately I donĀ“t think I will run into a Q41 anytime soon, as I have never seen one for sale here, and if IĀ“m to to change the engine I think I would go with something a little bigger.. Maybe a G-45. I have a G-62, but I think that will be too strong for scale aerobatics.

Westbender: Yes, it has a magneto ignition, but there is no point in changing to electronic ignition to save weight, as I would have to put lead in the plane to ballance it then. I donĀ“t know how the timing is set on a standard Q35, but I have assumed that itĀ“s set for max power, about 28Ā°??

Tipover: IĀ“m a little afraid to try a 6" prop, as I can only get it up to flying speed with the 8" as it is. But maybe an 18x8 or 10 would be the answer. A friend of mine uses an APC 20x8 on his Kavan 50 powered Diabolo, so I think I will try that prop before moving on.

But thanks again for your suggestions, keep them coming..:-)

NM2K

My Feedback: (14)

Pelle, I've owned/flown several Q35s. There really isn't much that can be done with them. However, they do fetch a pretty good price on R/C auction sites.

Coincidentally, you can pick up a chainsaw that is equipped with a Poulan 46cc engine for about what you can sell the Q35 for these days. With just a few parts purchased, you have an excellent R/C engine. No machining necessary, IIRC. Forget the Zenoah G45. Too heavy and expensive. Yes, I had one of those too.

Or, you can buy an already converted Poulan 46cc engine from Brillelli (they also sell the parts you need for a self conversion) for less than $300 with magneto ignition or $325 with electronic ignition. The latter is what I did. It is a fairly strong, yet light and compact engine.

I loved my old Q35. Lots of good memories with that engine, but it was really weak. Oh, and mine had been hopped up by Tom Rauch of Ohio back in 84 or so. Agony is flying a Byron Pitts or Christen Eagle with a Q35 for power. <G>

Pelle Gris

Hello again... I have just been testing the engine with an APC 20x8.. 8-8100rpm on the ground, with a stable idle around 13-1400 rpm. IĀ“m beginning to like this engine a lot better..
So IĀ“m gonna fly it tonight, and will let you know the result.

Westbender

My Feedback: (1)

Pelle, I highly doubt any engine with static timing would be set at 28 degrees. It would probably "bite" while starting, and certainly wouldn't idle very smoothly. I see your point about weight though. On the other hand, changing over to electronic ignition would allow you to go to full advance. Even if you didn't lose any weight after adding lead to re-balance, you'd still have higher power output. It is a very noticable power increase. Maybe RCIGN will chime in on this point. He is an expert on engines.

I've also heard of using offset flywheel keys to advance timing a little on magneto systems. Maybe that's another possibility. Any timing advance you can get, even if it's not all the way to 28 degrees, would help.

Pelle Gris

Just came back from the field where I tested the APC 20x8. The performance is much improved, and is about scale for an early Pitts S1 I guess. Speed is good, and vertical is also much improved. I can keep it in a sustained 40-45Ā° climb after takeoff without loosing too much speed. Just about perfect actually...

I only have one problem left to solve now. When starting the engine I can set the idle for a reliable 13-1400 rpm, but when landing after a flight I have to move the trim up quite a bit to keep it running. Is it the engine getting too hot, or is it the needle settings that are off? None of my other planes has cowls, so IĀ“m not sure how hot the engine gets.

Westbender

My Feedback: (1)

If your cowl has larger intakes than exits, it could be pressurizing during flight and causing the carb to go rich due to the pressure on the diaphram. You could try venting the diaphram cover into the fuse or at least outside the cowl.

Pelle Gris

I donĀ“t think thatĀ“s it, as it also happens on the ground during prolonged idle, but slowly. I can start the engine, set the idle, and after a few minutes I have to move the trim up to keep the engine running. And if I let it idle for too long, it dies when I advance the throttle. Could it be going rich or lean, combined with maybe heating up too much?
I think I will try baffeling the cowl, to see if that helps.

Flypaper 2

Sounds like it may be a little rich on the low mix. Starting up cold, it needs a little richer mix. once it warms up, it then becomes to rich. Lean the idle in till it hesitates when you open the throttle quickly, then back the mix out a bit till it doesn't hesitate. Sometimes when you start it cold, it may quit once then start again and it will stay running. When it does that its pretty close to being right on. Also, when it's running right the plug will be a tan colour. By the way, the standard prop for the Q35 is 18-8 but if it works good with the one you have, stick with it