Whoever can list the props pictured in the previous post in the correct order - highest rpm first - will win...












bragging rights!

David

Dave,


My bid is:

1st place - MA Series II
2nd place - Evolution
3rd place - MA Series 3

4th place - APC
5th place - Graupner

The first three will be significantly higher in RPM; and the last two may be reversed, despite the Graupner having a greater constant, on account of this APC being especially heavy for its size...

In the "olden days" when glow plug selection at the average hobbyshop wasn't as broad as it is today, the majority of us running baffled piston engines with air bleed carbs were pretty much forced to use idle bar plugs if we wanted an idle that was reliable below 3k rpm.

With today's selection of non idle bar plugs of various heat ranges and heat persistence, things might very well be different. But that is now and it does none of us any good back in the "olden days".

You can believe that when I made the transition from control line to R/C in the late sixties, I tried various non idle bar plugs that I had left over from C/L flying. None of them performed as reliably as the Fox idle bar plug. However, I was limited to only two or three brands of non idle bar plugs, as were most modelers. It is possible that some non idle bar plug could have performed as well, but I never stumbled across it.


Ed Cregger

I'll go:
MAS
GF3
evolution
apc
graupner

from highest to lowest

Ok, I need some info, please. I'll be using Pe's spreadsheet to calculate static thrust and HP. What would be an accurate prop constant value for the Evolution? He lists the other four props. A decent educated guess will do.

Thanks,
David

Great idea Rainedave! After running this test, you can tell Pe Reivers what prop constants he should use for the 11 x 6s.

My submission (highest to lowest rpm) including a wildarse guess at the actual rpm:

MAS - 13,400
GF3 - 12,800
evolution - 12,000
apc - 11,300
graupner - 11,200

OK, folks, we have the test data.

Temperature: 60° - clear, sunny and low humidity (for North Carolina)
Fuel: fresh Powermaster GMA 5% Nitro, 22% castor/synth blend
Glow Plug: brand new Fox Long (non idle bar)

All props are 11x6. With each prop I leaned the needle valve until RPM's dropped and then backed off a few clicks. So, these are peak numbers.

MA Black:
13,550
6.4 lbs. static thrust
1.15hp
66.9mph

MA 3 Series:
13,477
6.76 lbs. static thrust
1.24hp
66.5mph

Evolution (I chose a prop constant value of 1.15 which is lower than APC, but, higher than MA-S3):
13,146
6.62 lbs. static thrust
1.21hp
64.9mph

APC:
12,853
6.52 lbs. static thrust
1.18hp
63.5mph

Graupner:
12,406
6.91 lbs. static thrust
1.29hp
61.3mph

I'm waiting for comments...

David

Nice test David - thanks for sharing the data.

I have to admit, the APC result you got is a much higher rpm number than what I was expecting (that'll teach me for specifying rpm numbers!). I am now starting to wonder if there is more than one APC 11 x 6 design available. At our field, the best sport .46s are doing between 12,200 and 12,400 with the APC 11 x 6 whereas they will do near 14,000 rpm with the black MA.

Your test gives Pe Reivers a nice set of numbers to calculate new prop load coefficients for the 11 x 6 size.

Thanks HL. My APC is the older, early '90s type. I used to run it on my .40 Surpass in an Ace 4-40 way back around '91 or so. Maybe the current ones are different.

Here's an image with mine above and the one Tower shows below it.

David

Hmmm... looks pretty similar to me. [X(]

Here's one from my flightbox...

Does the hub on mine look different than yours?

BTW, this particular prop has more flight hours than any prop I've ever owned.

David

Dave,


I thought the Evo would be lighter than the MA Series 3...

Take note, everyone, the greatest static thrust and the greatest HP absorption, was produced by the prop which forced this engine to spin at the lowest RPM...


So much for those who still think a two-stroke engine must be as lightly loaded as possible, to properly do its job...

And if think that engine made more power at 12,400rpm than at 13,550rpm, I have a bridge for you. What that really means is that the prop load factors are not quite right for this size of prop. The thrust may be correct, there is no way to know without using a scale to actually measure it firsthand. RPM and thrust are not necessarily related, unlike rpm and power (in this rpm range, anyway).

Mark

I suppose I could redo the test using 10x6's. Problem is I don't have an Evo or MA-3S 10x6. That would bump the rpm's up and we could see if the HP figures go up as well. Maybe I'll test APC, MA Black and Graupner 10x6's over the weekend.

The good news is that I think I'll keep this engine. I bought it used for about $18 (missing its muffler). It's stronger than I thought it would be; not a bad sport .45 at all.

One thing we don't know is what this engine will do on a plane flying a steep upline. Loading up these props may cause the APC and Graupner to drop quite a bit in rpms. The lighter props will probably maintain their rpms better when loaded in flight.

David

David, what makes you think that the flight rpm will ever drop below the static rpm you got on a test stand?

Mark

What I mean is that the rpm will most likely drop from it's in flight level rpm, not the test stand rpm. However, some of the props I tested might very well drop more than others.

David

Here's mine...

HL, I would say they definitely came from different dies. I can identify a number of elements that are not exactly the same. The original die could have been reworked, but the two hubs are not identical.

If anyone's interested, I might do the same test with my AX .46.

David

You bet! I look forward to the results.

That would be very informative. If you could work in some 10x6 props that would be fantastic!

Guys, we may have to work up a fund to buy David a cold beer or two after all the hard work he is doing on our behalf.


Mark

HARRY HARRY - The APC numbers are probably higher because your not use to a Super Tigre LOL This makes 3 people test MAS props to show they are not truely a toothpick as you claim.

I think this particular engine most likely produces more torque at higher rpms than some other sport .45's, e.i., it has a flatter torque curve. When I test the AX .46 I might run my Magnum XL .46A, too. Maybe that will provide enough data to get an idea of the torque these engines produce around 12,000 or so.

David

I can't say how it's torque compares to other engines at higher revs but mine turns an APC 10x6 at 14,600 with 75/25 all castor fuel. However, just for laughs I tried a comparison against a new Enya 60-IIIB with both a 12x5 and a 13x6 props. The Enya of course is a baffled piston low down grunt stunt engine. Or so I thought.......

Enya 60-IIIB
12x5...9300
13x6...8600

ST GS45
12x5...10500
13x6...9100

Wow DU! I would say the ST .45 does produce some decent torque.

Just as a comparison, my Super Tigre Blue Head .40 - that's .40, not .45 - turns a Rev Up Pro 10x6 at 14,111 on 5% nitro:

http://www.rcuniverse.com/forum/fb.asp?m=8181884

David