Author Topic: Wasp with RSM carb performance (Read 2902 times)

Larry Renger · « **on:** June 06, 2009, 02:55:43 PM »

Since nobody else showed up at Whittier Narrows this morning (dunno why, don't they like rain?), I did some engine testing to get a handle on the performance of the Wasp with my design of venturi.

I was running 10/11/11 fuel, the temperature about 70 deg, pretty high humidity.

Tornado 5x3 3 blade 21,600 (great thrust, got to try flying with this puppy)
Tornado 6x3 3 blade 15,600
Tornado 7x2 wood 14,000 (remarkably little thrust)
Mas Air 6x3.5 14,250
Mas Air 5x3 3 blade E 15,000 (dang little thrust produced!)
APC 6x3 18,200
APC 5.7x3 20,400 (great choice)
APC 6x2 22,700 (pulls like a tractor!)
Cox Gray 6x3 16,200 (a good Tee Dee .049 will outdo this)

Needling was smooth with all props. I don't think the engine is all that sensitive to Nitro content, but I will do some cross-check with higher nitro at a later date.

My take is that the engine likes small props and gains power with higher rpm.

Bill Barber · « **Reply #1 on:** June 06, 2009, 03:14:41 PM »

Larry , seems like good performance with only 10% nitro .
Bill

John Crocker · « **Reply #2 on:** June 06, 2009, 04:44:54 PM »

Mine LOVE a combo of Powermaster 20/20 and Master Airxcrew 6 x 3.5. Plenty of pull and speed just right for me.

Larry Renger · « **Reply #3 on:** June 06, 2009, 05:03:09 PM »

Here is and Excel spreadsheet with all my current .049 and .061 data. OOPS, I can't post that file format, sorry. E-mail me if you want a copy, I can send it via e-post.

I need to go back and fill in a lot of blanks, especially Holland Hornet, Tee Dee and Medallion data. More reed valve engine data would be a boon too.

First, I have a box of "test props" someplace and need to find that.

minnesotamodeler · « **Reply #4 on:** June 06, 2009, 05:46:59 PM »

So is the venturi market-ready? How much?

Larry Renger · « **Reply #5 on:** June 07, 2009, 12:53:07 AM »

I dunno, talk to Eric. It is in his (capable) hands at this point. Anyone who has the machining capability, I can send the ACAD file, and you can make your own.

minnesotamodeler · « **Reply #6 on:** June 07, 2009, 06:22:42 AM »

Well, I can't; if it ain't wood, I don't mess with it much. My metal machining tools consist of a hacksaw, a drill and a file...

Someone? Anyone? Larry's done the dirty work; now please pick up that ball. There's a market here, guys...

Jan Holuszko · « **Reply #7 on:** June 07, 2009, 12:03:20 PM »

Ray,

I've been working on a venturi for the wasp engine myself. The design is a mixture of the Norvel and the TD. I've been trying to utilize easy to obtain or existing parts. So far, I'm using the wasp needle and detent spring.
On my original spray bar I made the fuel nipple too long and it interfered with the muffler. If I make it the size of the one on the TD then that problem is solved or, I could rotate the venturi 5 degrees like some Norvel models. My second and most troubling is the needle itself. It may be good for the tip of a dart but it requires a very small hole in the spray bar to turn the fuel off.
Making the venturi is not the problem, mating it with a good NVA is. Look at the NVA here http://www.texastimers.com/ And tell me what you think.

JAN

Larry Renger · « **Reply #8 on:** June 07, 2009, 04:48:59 PM »

That looks really neat. I would put the needle in front, but angled back. Best of both worlds. What is your fabrication method? Very nice machining. I have a micro lathe and mill, so my options are limited.

Robert McHam · « **Reply #9 on:** June 07, 2009, 05:26:09 PM »

Quote by Jan:
"tell me what you think."

What I think is that the solution to the NV problem, at least for a few folks, is already in their hands.
By this I mean that a viable NVA can be had from the older product engines.
It is my understanding that this is the 128 fine thread assembly that can easily be used in such a project as this.
I know, not everyone has these but some of us do. Some of you may have a bunch of these things.
Check out your engine/ parts stash!

Robert

Jan Holuszko · « **Reply #10 on:** June 07, 2009, 07:26:33 PM »

Larry,

The needle will work fine in the back if I angle it.

I start out with 1/2" 6061-t6 aluminum plate usually around 7" long and3" wide. I mill the length parallel. I set my axises 0,0,0 and run my program to blank out the body. Afterwards. I spot drill, then drill, then do the taper. I ground a dull key seat cutter to a .125 radius and milled the side where the spray bar will be. When done I flip the stock over and do the same thing. I then cut them out on the band saw. Now I have to do piece work. I clamp up and mill to length and do the minor diameter. Flip on its side and drill for the spray bar and drill and tap for the securing screws.

Larry Renger · « **Reply #11 on:** June 08, 2009, 09:24:58 AM »

Way out of my league! I think you should contact Eric Rule, he might be interested in a marketing deal with you! Are you in the position to sell these? I would be interested in purchasing one.

minnesotamodeler · « **Reply #12 on:** June 08, 2009, 11:31:21 AM »

And me too. I agree, just angle the needle back a little a la Norvel, it'll work fine. Put me on the purchase list!

the Texas Timers needle looks very useful, too.

jamtx · « **Reply #13 on:** June 08, 2009, 02:38:48 PM »

Very nice! If you sell any I'll take one.

Larry Renger · « **Reply #14 on:** June 23, 2009, 07:11:46 AM »

Jan sent me one to test. I am planning to fly it today! Absolutely beautiful machine work and fit the crankcase like a glove.

Larry Renger · « **Reply #15 on:** June 24, 2009, 12:25:06 AM »

The system has a few bugs, but I got a couple of really good runs through the complete pattern. I have forwarded all my comments to Jan, and he is interested in making the needed changes. I was flying with muffler pressure and a uniflo tank, things I rarely do. I think he will have to resize the venturi bore to handle a balloon tank on simple suction (I did on my design). I don't think that the performance of the engine will suffer from a bit more restriction (mine didn't).

Hang in there, gang, we're working on it, and someone will have a superb unit available soon, I expect.

In the meantime, I modified a stock carb by sealing the rotor in place with blue locktite, adding a washer to allow the spring-clip nut to lock the rotor in place as a backup, and sealed the needle with plumber's teflon putty. I will try to break in that engine this week and test it soon.

minnesotamodeler · « **Reply #16 on:** June 24, 2009, 12:50:01 AM »

Quote from: Larry Renger on June 24, 2009, 12:25:06 AM

T
In the meantime, I modified a stock carb by sealing the rotor in place with blue locktite, adding a washer to allow the spring-clip nut to lock the rotor in place as a backup, and sealed the needle with plumber's teflon putty. I will try to break in that engine this week and test it soon.

Just about exactly what I have done although I have not run it yet. Still prefer a real live genuine venturi... I will wait patiently.

Larry Renger · « **Reply #17 on:** June 30, 2009, 07:27:54 AM »

Well, I have finalized the design of the RSM venturi and sent it to Eric. He will get quotes and then we will see! In the meantime, I started to break in the engine with the modified AP carburetor, but it leaked fuel out the front end like crazy. HP exchanged it with no argument. I will get to breaking in the new one ASAP.

Incidentally, I decided to check out the quality control, so disassembled three brand-new motors. The piston/cylinders are all individually fitted nicely, but are NOT interchangeable. The bores are different enough that you can't just drop Piston A into Cylinder B or C and get a useable fit. The bore diameters were ALL different. Interesting. I'll put a micrometer on the crankshafts and see how they measure up.

peter jurczyk · « **Reply #18 on:** June 30, 2009, 12:23:03 PM »

Larry on the modified ap carb what did you do with the air bleed screw.The washer dont fit with it in there.The hole for the air bleed looks like it goes to nothing.

minnesotamodeler · « **Reply #19 on:** June 30, 2009, 03:55:09 PM »

Right...take it out and throw it away.

peter jurczyk · « **Reply #20 on:** June 30, 2009, 06:43:48 PM »

Thanks for the reply.But if it dont do anything whats it there for ?.Thanks

minnesotamodeler · « **Reply #21 on:** June 30, 2009, 07:40:16 PM »

It's an eccentric-head screw (you'll see when you go to take it out). Works like a littler cam to adjust the idle position of the carburetor. Not needed when you go to a locked-open carb. Take it out and, well if you insist, keep it in case someone comes looking for one...I threw mine away.

Larry Renger · « **Reply #22 on:** June 30, 2009, 11:24:27 PM »

I agree the screw isn't needed, but that is a nice little spring with it, you never know when you need one..... And besides, how many excentric screws are readily available.

Bill Adair · « **Reply #23 on:** July 01, 2009, 09:03:30 PM »

Ran my AP Wasp again today, but it's still not completely broke in!

I've decided to go ahead with the Cox TD venturi installation, and not worry about getting a baseline RPM reading for comparisons. The R/C carb is so darn inconsistent, that it's difficult to find a peak RPM setting, and get it to stay there long enough to get a tach reading!

Today it was turning a tad over 16K, with an APC 5.7 X 3 prop, using Brodak 10% fuel. Note that this is different fuel, than the blend I was using before. It seemed to be breaking in very slowly, with the extra Castor lube.

Bill

Larry Renger · « **Reply #24 on:** July 01, 2009, 09:16:16 PM »

Immediately after a run, put your finger on the crankcase ahead of the venturi. It should be cool. If it is hot, the crankshaft fit is too tight. I had a recent one like that, and the run was all over the map as it overheated, slowed down, cooled and then cycled again.

jim gilmore · « **Reply #25 on:** July 01, 2009, 09:36:50 PM »

Would it eventually break in or is it a lost cause ?

minnesotamodeler · « **Reply #26 on:** July 02, 2009, 07:07:40 PM »

A couple of my engines had tight cranks, even after quite a bit of running...I took them apart, put toothpaste on the cranks, chucked 'em in my hand drill and spun them for about 10 or 15 minutes. Seemed to loosen them up a little, certainly not too much. I'm not necessarily recommending this, engine guys will probably chime in with various levels of fits.

Bill Barber · « **Reply #27 on:** July 02, 2009, 09:29:00 PM »

Ray , have a friend that used toothpaste on Norvel cylinders to loosen them up.
Mainly used them for free flight , but they ran well for him. Not sure I would do it !
So did they run well for you after used the toothpaste ?
Bill

Larry Renger · « **Reply #28 on:** July 03, 2009, 01:12:34 AM »

On the AP, you can indeed lap the crank to the case. On Cox, Norvel and Brodak, you should polish the crank down to fit. The reason is that only the AP has a bronze bushed case. With the others, you will imbed grit in the aluminum and I believe this reduces the life of the engine.

To polish a crank down, take a strip of 400 grit W/D paper about the width of the crank bearing area. Oil it well and wrap it in a "U" around the shaft (which is chucked into a power drill on low speed). Run the drill while pinching the paper. This exerts a very even pressure on the shaft. When I used to do this to Tee Dees, they would test out has having better than spec roundness, wavieness and finish. My QC guy was impressed!

The crank and case should be cleaned with solvent and dried. At that point give the crank a spin in the case. It should go around several times.

If you lap the shaft or polish it as above, after getting a satisfactory fit, do the polish routine one more time, but with 2000 grit paper. Gets to look like a mirror!

minnesotamodeler · « **Reply #29 on:** July 03, 2009, 07:59:28 AM »

Quote from: Bill Barber on July 02, 2009, 09:29:00 PM

Ray , have a friend that used toothpaste on Norvel cylinders to loosen them up.
Mainly used them for free flight , but they ran well for him. Not sure I would do it !
So did they run well for you after used the toothpaste ?
Bill

Yes, they showed some improvement...I probably didn't go far enough, being careful to not go too far. Both still a little tight but better. I'm tempted to take them apart and do it again...perhaps, given Larry's warning, I won't.

I remember there were combat engines in the 60s that didn't run to their potential until the second piston/sleeve; took that long to loosen up the lower end.

Larry Renger · « **Reply #30 on:** July 03, 2009, 09:49:21 AM »

You can do the crank polish routine as often as you like until the engine runs right. Why suffer?