Author Topic: PA .51 question (Read 3240 times)

Dave Heinzman · « **on:** June 05, 2006, 05:40:26 PM »

Hi Randy,
Thanks for being available for questions about engine setups. I have a piped PA .51 in a Tempest II model. Using a bolly 12.25 x 4.25 prop, I set the launch RPMs to 10,100 - 10,200 pipe is at 17.5". After takeoff and a few laps the engine wants to speed up too much and stay there. If I take the bolly off and install an APC 12.25 x 3.75 prop and change nothing else, ground RPMs then become 9,400 - 9,500 and the engine settles into a fast four cycle with some break at the tops of maneuvers - pretty much a good run. Somehow, the heavier APC seems to settle the engine down and not want to speed up. I would eventually like to find out why the bolly doesn't work as it should. My .51 venturi diameter is .182. I'm using power master 5/22 fuel, a six ounce magnum style tank. Fuel consumption is 5.0 ounces for a 6.5 minute flight. Am I missing something obvious?

Bill Little · « **Reply #1 on:** June 05, 2006, 06:31:55 PM »

Hi Dave,

Have you checked the pitch on the Bolly? I have run a PA 51 quite a bit with a 12 X 4.25 Bolly 2 blade with the pipe at 17 1/2, 5% Sig Champion. Exact same set up in a 53 oz. Saturn based plane and a 63 oz. Geo "Bolt" XL. I would like to give you a rpm reading, but when Randy is around we only set them by ear (no tachs allowed

), so I don't have a clue as to what the rpm is!

But the run is exactly as you have mentioned. A solid 4 cycle that begins with in a 1/2 lap of take off with a blip when the engine is loaded.

Randy will jump in soon.

Bill <><

Dave Heinzman · « **Reply #2 on:** June 05, 2006, 08:51:21 PM »

Hi Bill,
Yes I checked the pitch on the bolly, my guage shows about 4.5 . I have tweaked the pitch up to 5.0 but after time they settle back to the 4.5.
I'm using a homemade Hooptee pitch guage from a magazine article, I should try a different guage and see what the reading is.
Dave

Bill Little · « **Reply #3 on:** June 06, 2006, 07:37:00 AM »

Quote from: Dave Heinzman on June 05, 2006, 08:51:21 PM

Hi Bill,
Yes I checked the pitch on the bolly, my guage shows about 4.5 . I have tweaked the pitch up to 5.0 but after time they settle back to the 4.5.
I'm using a homemade Hooptee pitch guage from a magazine article, I should try a different guage and see what the reading is.
Dave

Hi Dave,

I was talking withj Randy and Stan Powell late Saturday afternoon about setting the pitch on the Bollys. Randy gave a temperature that the resin must reach for the proper tweak to be maintained. His technique for tweaking Bollys is to heat them and take them to a little past your desired pitch, then work them to the pitch desired as they cool down. This really keeps them from returning to what they were molded. I am afraid I will not give the correct temp, so I'll wait on Randy to say.

Bill <><

RandySmith · « **Reply #4 on:** June 06, 2006, 11:00:47 AM »

Quote from: Dave Heinzman on June 05, 2006, 05:40:26 PM

Hi Randy,
Thanks for being available for questions about engine setups. I have a piped PA .51 in a Tempest II model. Using a bolly 12.25 x 4.25 prop, I set the launch RPMs to 10,100 - 10,200 pipe is at 17.5". After takeoff and a few laps the engine wants to speed up too much and stay there. If I take the bolly off and install an APC 12.25 x 3.75 prop and change nothing else, ground RPMs then become 9,400 - 9,500 and the engine settles into a fast four cycle with some break at the tops of maneuvers - pretty much a good run. Somehow, the heavier APC seems to settle the engine down and not want to speed up. I would eventually like to find out why the bolly doesn't work as it should. My .51 venturi diameter is .182. I'm using power master 5/22 fuel, a six ounce magnum style tank. Fuel consumption is 5.0 ounces for a 6.5 minute flight. Am I missing something obvious?

HI Dave

That is one of the best props we have found for the 51, I am using the exact prop on my 51 in my Katana. I use 5% 20 oil in cool months and 10% 20 oil in warm months
Bolly 12 x 4.25 3 blade, It should set on the ground just crackling back and forth into a 2 cycle, them it should drop to a solid 4 cycle just within 1 lap after launching, There are several hundered running this same setup. If you go several laps then the engine starts running fast there is a problem somewhere else, most likley either getting hot from too much load, too little cooling or fuel delivery.
By the way 4.5 to 5 pitch is too much, try 4 to 4.25

Are you into a 2 stroke in level flight?
does the motor change after the first 10 laps or is it constant thru out?
What size plane
what is the weight of the plane?
Is the header tounching the corner of teh tank?
is the needle touching the fuse sides?

Randy

Dave Heinzman · « **Reply #5 on:** June 06, 2006, 05:01:26 PM »

Thanks Randy, the plane is a 690 square inch Tempest II 64 ounce on 64 foot lines. The .51 with the bolly on it speeds up into a two stroke within the first three to four laps. Header is close but not touching the tank -- needle valve is not touching the fuse. I'll have to try running it with the cowl off, if that isn't it then I'll try a different tank.
Dave

RandySmith · « **Reply #6 on:** June 06, 2006, 07:38:14 PM »

Hi Dave

The motor shoul d always unload and go richer in the air , never leaner.
Let me know how it does with the changes

Regards
Randy

Jim Pollock · « **Reply #7 on:** June 07, 2006, 05:26:33 PM »

Dave,

How many cooling outlet holes do you have in the cowling ahead of the header?
You problem kind of sounds like the one Ted Fancher ran into with his Trivial Pursuit.
All the cooling was exiting the cowling before it reached the header and pipe. He had to
put tape over some of the outlets. After reading that, I installed intake scoops on my cowling aimed at the header. There were no outlet holes at all until neary the midpoint of the pipe. My .51 ran flawlessly on a Bolly 12 X4.25 repitched with about .2 more pitch at the last station on my prop guage.

Jim Pollock, For what it's worth

Dave Heinzman · « **Reply #8 on:** June 07, 2006, 06:45:52 PM »

Thanks Randy and Jim,
I have no cooling vents befoe the header, there is a7/8" x 3.5" cooling vent in the cowl right where the header and coupler are. Then the pipe goes under the landing gear and is open the rest of the way. I really like this motor, just neeed to work with it some more. If I can I'll try to post some pictures.
Dave

Bill Little · « **Reply #9 on:** June 08, 2006, 01:07:06 PM »

Hi Dave,

Find a way to increase the front cowl opening (may not be needed), and close up the hole over the header. That is what everyone seems to be doing contrary to the original method shown on many of the original pipe planes where there was an opening over the header pipe connection. I had to "retro fit" my cowling to fill in that opening.

Randy can explain.

Bill <><

Dave Heinzman · « **Reply #10 on:** June 12, 2006, 05:03:28 PM »

OK guys I had a chance to fly the Tempest this weekend with the cowling off and there was no difference. Takeoff and a few level laps and the engine leans and speeds up. The more I fly the worse it gets. I did not try another tank yet I don't have one ready to go -- poor planning on my part. Tank has been flushed out and checked for leaks this past winter. The tank installation is good in my estimation -- not loose or shifting around. I'm starting to think that the fuel could be foaming. I always balance my propellers. The engine mounting is solid and straight. I'm going to try installing a du-bro crap trap filter instead of the blue master airscrew that I have now (yes, i epoxied the two halves together). One time I had a hemi head fox .35 on an original Nobler that never held a good needle setting almost like what I have now. A Brodak .40 on the same plane ran OK. So I have a couple of questions: Do higher compression engines have a tendency to vibrate and cause fuel foaming? Is a PA .51 considered a high compression engine? It doesn't feel like it when I flip the propeller. I have heard of putting Armour All in the fuel to stop the foaming. Is something like that OK to use for an extended time? Any thoughts you have would be appreciated.
Dave

Steve Fitton · « **Reply #11 on:** June 12, 2006, 06:43:17 PM »

Dave,

When I used armor-all, it stopped foaming but killed plugs. Only got 100 or so flights per plug, then flameout

I have a DS 40 in a Nobler that does the same thing, no idea what is causing it. Still working that little problem.....

You gonna go to brodaks? maybe we can have a listen and look at your PA ship and see whats going on. Sometimes multiple sets of eyes and ears are a good thing.

Steve

Dave Heinzman · « **Reply #12 on:** June 12, 2006, 08:24:59 PM »

Hi Steve,

I'll be at Brodak's on friday and saturday. See you then. Thanks for the info.

Dave

Steve Fitton · « **Reply #13 on:** June 12, 2006, 08:42:48 PM »

Cool. Don't forget appearence judging is Thursday afternoon now (I think).

I'll show you the "Mirror image" Nobler I did in homage of your '52 ship. I reversed the colur scheme on mine.

Steve

Tom Perry · « **Reply #14 on:** June 13, 2006, 07:07:36 AM »

Dave,

Just a shot in the dark on my part but have you considered trying a slightly cooler glo-plug?

Bill Little · « **Reply #15 on:** June 13, 2006, 07:39:03 AM »

Hi Dave,

Flying with the cowl removed may not have actually helped the cooling of the engine-pipe system. Sometimes a system like Mr. Rabe builds into his planes where the air is forced over the engine is necessary.

Having the opportunity to receive Randy's help on frequent occasions makes it real easy for me to set up his systems. One thing in particular that he made me do is what I said in my earlier post. There are only two opwnings on the airplane: the air intake at eh nose of the cowl, and an opening just big enough to get teh pipe inand out of on the bottom of the fuselage. That forces the air to move over the whole engine/header/coupling and down the pipe before it can exit.

I remember Ted having to close up all the extra holes on the nose (cowl) of one of his Trivial Pursuits because it allowed too much air to escape before the system could be cooled.

Just a thought. But the openings over the header/pipe connections are no longer used.

Bill <><

Bill Little · « **Reply #16 on:** June 13, 2006, 07:48:24 AM »

One thing you may or may not know that Randy makes us do is that after you crank the engine and remove the battery, you put your finger over the uniflow vent to pick up the rpm. This heats up the engine a little quicker. Then the engine is set to pretty much the same sort of "cackle" that a ST 60 has on the ground. Mostly 4 cycle but hitting a 2 every now and then.

After re-reading your original post, it is puzzling as to why you have to drop the rpm so much when going to a 2 blade with less pitch than the 3 blade Bolly.

Dave Heinzman · « **Reply #17 on:** June 14, 2006, 03:51:09 AM »

Hi Bill, it takes me a while to get my mind wrapped around covering up the hole by the header coupling to increase cooling of the engine. I am going to do that. Probably this evening.
Dave

RandySmith · « **Reply #18 on:** June 14, 2006, 11:53:25 AM »

HI Dave

The plane should always run cooler with teh cowl on than with it off,
and You can use tape to block off the hole. I may suggest making the rear hole more open if it is small
The other thing I would do is use 10% nitro fuel, this will give more power and let you set the engine a bit more on the rich side.
We use 5% in cool months and go to 10 % in hotter months...the hot months are here now
please let me know how this works

Randy

Dave Heinzman · « **Reply #19 on:** June 14, 2006, 07:52:07 PM »

Hi Randy,
I did some flights this evening with the header coupler cowl vent coverd and it did ok, wasn't a completly different run, but it was manageable.
My rear opening in the fuse for the pipe is huge so I'm good there.
I am using 5% fuel It was about 68 degrees this evening. I'll try the 10%. I think I'm starting to get on my way with this model now. I sure appreciate you taking the time to respond to my question. BTW I'm at least the 3rd owner of this engine, it has # 193 ( I think ) engraved on the case, also somebody wrote on the inside cover of the box that the engine came in, .015" + ..008" = .023" head shims I'm assuming thats what I have in there. Does that sound right?
Dave

RandySmith · « **Reply #20 on:** June 14, 2006, 08:04:48 PM »

HI Dave

If it is a series 1 PA 51 that is too little gaskets it should be 28 to 32 thou

If it has a series 2 head on it it should be 15 thou gaskets

series one head looks like a high compression Stunt sqiush double bowl, all were rounded off at the top outside

series 2 head has a single hemi and a very small squish band, some are rounded off outside on the top and the newest ones are ssquared off like the PA 61 65s

That engine sounds pretty old

Regards
Randy

Bill Little · « **Reply #21 on:** June 25, 2006, 12:19:31 PM »

Hi Dave,

How are things working with the .51? Curious to see if you got it sorted out.

Bill <><

Steve Fitton · « **Reply #22 on:** June 25, 2006, 10:38:37 PM »

Bill, I'm sure Dave can give more details, but it seemed to run great at Brodaks. He did have the header cowl exit taped off, don't know if he changed head shims or anything else.

Steve

Patrick Rowan · « **Reply #23 on:** June 26, 2006, 01:14:17 PM »

I launched Dave for his 2nd PA flight on Sat.
He had a good engine run & nice looking pattern.

Bill Little · « **Reply #24 on:** June 26, 2006, 03:33:07 PM »

Thanks Steve, and Pat. I couldn't see a reason that there would be run issues with the 51 unless it had been really abused by the previous owners.

Bill <><

Steve Fitton · « **Reply #25 on:** June 27, 2006, 05:59:17 AM »

I would point out, though, that he ran the APC 12.25x3.75 that ran okay even at the beginning of the thread. Maybe it still doesn't like the Bolly for some reason. For obvious reasons he stuck with the prop that worked at the contest.

It would not have occured to me to run the APC on a piped PA, but it worked suprisingly well

Steve

Dave Heinzman · « **Reply #26 on:** June 28, 2006, 06:16:25 PM »

Hi Bill, I went to Brodak's expecting to have run problems but it didn't happen. I've flown this model enough to know it was close to having the the speed up thing happen but it didn't. The only difference bettween home and Brodak's is 300ft ( I think ) higher of altitude. I can get good runs here at home with the APC but not easy as it was there.
Going from Randy's last post here I believe I have a series 1 PA .51 so that means that I need to add some head shims to be at the range of .028" - .032"head spacing. I'm at .023" now. I talked to Randy and he is sending me some shims to try. I'll let you know how it works out.

Dave

Bill Little · « **Reply #27 on:** June 28, 2006, 10:52:53 PM »

Thanks, Dave, I'm glad it worked out for you at Brodak's. I really like my 51!

Randy really knows his engines! He helped me a ton at the last local contest getting my PA 61 to run perfect.

Let me know how it comes out.

Thanks!
Bill <><