Mach racer and K&B .61 ringed PDP (Full Version)

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RSOSKE2 -> Mach racer and K&B .61 ringed PDP (5/1/2008 2:55:08 AM)

For kicks I Desided to send off my K&B MR. Lee for the pdp mods and stuffed it in my Model tech mach racer. I am wanting to keep the rpm down to the 12,500 mark. Right now its taching a little over with a 11*9 APC prop. Any suggestions to keeping the rpms down and not going with a larger prop as I cant do this since it will be to close to touching the ground.

Randy



rainedave -> RE: Mach racer and K&B .61 ringed PDP (5/1/2008 3:53:55 AM)

I would try various brands of 11x9's since the loads from brand to brand can vary quite a bit.

David



speedster 1919 -> RE: Mach racer and K&B .61 ringed PDP (5/1/2008 11:00:08 AM)

Go to a 3 blade prop and drop down to 10" while your at it...........



speedster 1919 -> RE: Mach racer and K&B .61 ringed PDP (5/1/2008 11:08:37 AM)

Go to a 3 blade prop and drop down to 10" while your at it...........
http://www.masterairscrew.com/index.asp?PageAction=VIEWCATS&Category=12
Or even a 4 blade that can be expensive. I think the 10x7x3 would not go past 12,500, but none of my K&B's are PDP. The 11x7x3 would surely work...........



panzerd18 -> RE: Mach racer and K&B .61 ringed PDP (5/1/2008 11:17:52 AM)

If you need to drop RPM and you can't go larger in diameter then you can always go coarser in pitch, say 11x10?

Why don't you just adjust the end point for the throttle so it doesn't open fully when you go full throttle on the transmitter.



blw -> RE: Mach racer and K&B .61 ringed PDP (5/1/2008 2:23:43 PM)

I'm not sure of the exact RPM limits that Clarence recommended to me with the same engine that I have, but he suggested a 11x7 for the max.



Ed Cregger -> RE: Mach racer and K&B .61 ringed PDP (5/1/2008 2:31:29 PM)

I'd drop to a 10x9 or 10x10. One of the Jett .90's uses this same prop. Not that the Jett .90 has anything to do with your K&B .61.

I wouldn't expect massive torque from the Lee modified K&B .61 PDP.

Some of the earliest K&B .61's were screamers with an 11x7. The later editions were much more sedate. Fortunately, spare parts (crankshafts) aren't that expensive to replace, as long as you don't hole the crankcase.


Ed Cregger



RSOSKE2 -> RE: Mach racer and K&B .61 ringed PDP (5/2/2008 12:42:58 AM)

Thanks for the input. Ill try the 3 blade and see what that does. I didnt want to adjust the end stop cause we all know that 3/4 open on most two strokes is almost max rpm anyway, atleast all the ones ive played with. I have the throttle curve set on the transmitter so that have throttle is have the rpms, etc. ITs something to play with and Ill let you all know this weekend how it went



blw -> RE: Mach racer and K&B .61 ringed PDP (5/2/2008 4:17:04 PM)

I would tach it with a good 11x7 prop and use that RPM number as the baseline for other props. I agree with Ed that the crankpin is the thing you need to be careful about.



Ed_Moorman -> RE: Mach racer and K&B .61 ringed PDP (5/2/2008 7:09:14 PM)

Take the gear off and hand launch or make a launcher out of PVC and don't worry about the size of the prop. I have used the same launcher for different planes.



RSOSKE2 -> RE: Mach racer and K&B .61 ringed PDP (5/3/2008 5:18:34 PM)

I just returned from the flying field and I have to say that the engine is a very fine running machine. I have read people compare the k&b .61 to the new 40 size for power wise. I have ran mds .48 os 46ax and others in the mach racer and the k&b by far out does them all. I fly a p-51 with a magnum xls 61 and I would say its right there with it. I have to give MR. lee is due for building a engine back in the days that still has its place today.



Ed Cregger -> RE: Mach racer and K&B .61 ringed PDP (5/4/2008 5:25:02 AM)


quote:

ORIGINAL: RSOSKE2

I just returned from the flying field and I have to say that the engine is a very fine running machine. I have read people compare the k&b .61 to the new 40 size for power wise. I have ran mds .48 os 46ax and others in the mach racer and the k&b by far out does them all. I fly a p-51 with a magnum xls 61 and I would say its right there with it. I have to give MR. lee is due for building a engine back in the days that still has its place today.






The old top of the line, baffle piston sixty engines, weren't that far off in power from some schneurle ported engines. Even though it is a baffle piston engine, it is still a .60 and it is usually capable of swinging more lumber than any highly tuned .40 - .52. We would all like to think that our newer smaller engines are more powerful than the older sixties, but, truthfully, they are not.

Ed Cregger



Broken Wings -> RE: Mach racer and K&B .61 ringed PDP (5/4/2008 2:41:23 PM)


quote:

ORIGINAL: Ed Cregger


quote:

ORIGINAL: RSOSKE2

I just returned from the flying field and I have to say that the engine is a very fine running machine. I have read people compare the k&b .61 to the new 40 size for power wise. I have ran mds .48 os 46ax and others in the mach racer and the k&b by far out does them all. I fly a p-51 with a magnum xls 61 and I would say its right there with it. I have to give MR. lee is due for building a engine back in the days that still has its place today.






The old top of the line, baffle piston sixty engines, weren't that far off in power from some schneurle ported engines. Even though it is a baffle piston engine, it is still a .60 and it is usually capable of swinging more lumber than any highly tuned .40 - .52. We would all like to think that our newer smaller engines are more powerful than the older sixties, but, truthfully, they are not.

Ed Cregger


Smiles...



RSOSKE2 -> RE: Mach racer and K&B .61 ringed PDP (5/4/2008 7:07:12 PM)

I am starting to think that way. Went out again today and even the jet flyers were asking what engine im using, and they dont beleive its a old 70s. The older crowd at the feild remember when they used these and are thinking of going back to them after they saw the results. I like this better than my os engines by far. And its runs much better than them on the 5% nitro. I have had no trouble with the perry carb that the old timers said would have problems



Broken Wings -> RE: Mach racer and K&B .61 ringed PDP (5/4/2008 7:31:12 PM)

Try an HB PDP or one of the Super Tigre Blue Head PDP engines.

The Perry carb likes clean fuel, Use one of the OS felt type fuel jug filters and the problems solved.

Baffle piston engines work.



Ed Cregger -> RE: Mach racer and K&B .61 ringed PDP (5/5/2008 7:01:02 AM)


quote:

ORIGINAL: RSOSKE2

I am starting to think that way. Went out again today and even the jet flyers were asking what engine im using, and they dont beleive its a old 70s. The older crowd at the feild remember when they used these and are thinking of going back to them after they saw the results. I like this better than my os engines by far. And its runs much better than them on the 5% nitro. I have had no trouble with the perry carb that the old timers said would have problems






Perry carbs were advanced for their era and solved many problems, not created them. One has to keep the fuel clean and the o-rings fresh, but you should do that with any carb, not just Perry.

Perry pumps could be problematic if one didn't follow the rules, such as no petroleum based oil for after run oil. I ruined quite a few pumps, both Perry and Robart until I learned this lesson. Don't know how I missed the info in the instructions, but I did and I paid the price.


Ed Cregger



LeeHop -> RE: Mach racer and K&B .61 ringed PDP (5/5/2008 4:12:41 PM)

Ed so what do you use for a non-petroleum-based after run oil?
Tnx



Ed Cregger -> RE: Mach racer and K&B .61 ringed PDP (5/5/2008 5:30:58 PM)

Synthetic based Air Tool Oil. There is at least one ARO that is advertised as being YS safe, but I forget the name of it. Anyone?


Ed Cregger



larry@coyotenet -> RE: Mach racer and K&B .61 ringed PDP (5/6/2008 12:25:58 AM)

People constantly underestimated the K&B 61, especially with the PDP porting. I would rate your engine as the equal of any current 60 and superior in handling and longevity. Having flown since the early seventies I love to haul out some of my old engines, like the K&B 40 and 61 and fly them in period planes. Most guys are shocked at the speed of a good middle seventies pattern plane with an engine like a K&B 61 turning 12,500 rpm! I had forgotten just how fast a Mach 1 or Kaos would go, not to mention a Banshee!

Larry



Sport_Pilot -> RE: Mach racer and K&B .61 ringed PDP (5/6/2008 4:31:08 PM)

Fresh castor oil is the best after run oil.



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