Mr Cox

I think that the HP values from manufacturers are highly inflated and it doesn't really mean much, the proof is in the running...

I don't understand what you mean by "if unloaded", the thrust/power calculators are with stationary air/engine. In an moving airplane the load on the prop will drop as the air is now moving and the rpm will go up, even if there is no change in engine power.

Pond Skipper

I checked some data from a well flown plane that has over 100 flights with a Top Flight wood 11x4 the speed and thrust was spot on to what I was getting out of the 1.1hp rated engine from the manufacture. I think the software's high speed predictions are more theoretical top speeds as the software cant compute the plane design, weight and size. The software is still better than nothing.

The hp rating from the car manufacture might have been done on a fancy dynamo meter setup, knowing the engine is peaking out at 39.74k running wide open on the ground .65hp at 31k seems possible. The RC car guys have a lot more support for their products giving them accurate data we airplane guys have to struggle to get.

aspeed

A lot of manufacturers will say 2,000 to 20,000 rpm and 1.2 HP (or whatever) People buy them and expect a huge prop to turn that, and idle at that. I have seen it so may times. What they often mean is to prop it less than say 20,000 and not to try to get less than 2,000 idle. The car engines are much different than an airplane. If the highest torque reading is at maybe 32,000 rpm, then maybe it should be propped for 28,000 rpm, and then it will unload to 32,000. 40,000 on the cars is just unloaded with a flywheel, and is really just to impress the car guys. They are often run at half of that rpm, and need acceleration out of the corners. A plane would need such a small prop that would barely pull a plane to get 40,000 rpm. As an example there is a Novarossi .21 2000 that a lot of control line speed guys use with a high rpm quote, but the guys prop them for 24,000 in the air. You still have to push the air.

Pond Skipper

I do plan on posting a video of some static testing for all to see, most likely starting with a 4.75x4 "early prediction" around 29.5k static .38hp / 112mph / 20oz thrust so if unloaded perhaps 33k /125mph.

Yes agreed Alan, I want a good top end for passes but expect solid acceleration that wont be scrubbed off in the turns so torque / thrust really needs to be near the engines peak break hp. If the .07 is 31k /.65
I want to shoot for 33k unloaded for good passes with plenty of meat left for the turns.

Pond Skipper

I was over on the dark side looking at props these speed guys are using some serious pitch can you imagine a 6.5 x 12.5 at a reported 32k static whaaaaat!!

They are in the cough cough 300 mph club pulling thousands of watts 3Kw and up. I have some brushless engines one is 120mm in dia. can pull close to 200 amps swings a 36in x 14 composite prop and scares me when I fire it up past half throttle on just 12S. Thus far I have only gotten it up to 90ish amps for a brief bursts to see what 3/4th throttle sounded like.

Anyway their is a German chap that makes carbon props over on the watts side and is now getting into the smaller ones.
I sent him a message for strong hub IC 4 x 6 / 3mm bore cant hurt to ask we shall see if it happens I will post a link for those that want to try this with .07 to .09 size engines should he add it to his list.

MJD

My Feedback: (1)

The guy running those props on his MB 40 is the same guy that owns over 2000 engines, I suspect he assisted or paid the tooling cost. I got domestic quotes in the $250 mark to generate a tooling epoxy mold from a master plus cost of the props after in small lots.


4.25 x 5.25

http://eliminatorprops.com/store/ind...products_id=60

And a possible feedstock prop based on a design from the 1700's:

http://eliminatorprops.com/store/ind...products_id=69



Single blade..?

http://eliminatorprops.com/store/ind...products_id=23

A strong CL .15 will turn these from 34-35 (middle of the pack speed engines) to 42-43k (top F2A engines). Seems to me they'd be about right for the 27-30k club on smaller displacement.

aspeed

I had a 4 & 1/4" - 7" prop a long time ago. Pretty hard to find even then in the late 1970s. I am not realllly that old. I think Revup , it was wood anyway. The TD did not have enough power to do much with it. Maybe an .06 or .074 might. I made a mold of it and the wood prop was splinters. It is not really hard to make a mold. Just time consuming, and waiting for a cure. The layup process take a few tries to get right with no bubbles, or not too thick. For $5 or even $15 it is worth it for someone else to do it. I would still cry if it hit the ground either way.

Pond Skipper

Thank you Mike good props to try the 4.25x5.25 looks promising with just a clean up and balance.
I need to gear up for a bench test and see what the .07 can do on the pipe and go from there.
Its a true ABC engine so break in wont take much fuss.


I have some speed props from back in the day white nylon such as a 5x8 another is a 6x10
always been a marvel and how they could get some use on my end. The massive torque and rpm of the
brushless motors are demanding robust props that are becoming useful for the thumping of IC engines.
The only down fall is they tend to be a bit too aggressive in pitch at the hub.

aspeed

The high pitch props were big back in the day when nitro was allowed. You got a lot of power that way. Now most competition is limited to 10% or even 0% nitro, so it is all about revs. Electric is a whole new ball game, as you can change the # of winds etc. I still think the motors are revving way too high, and they should get more bite, as in more pitch. At least for the longevity of the motors if nothing else, but also in the quest for speed.

Pond Skipper

https://www.apcprop.com/v/PERFILES_W...tDatafiles.asp

Using the charts I checked the Norvel AME .061 on the Profi pipe

4.2x4 / 25.5k rpm / .143 hp static
4.2x4 / 28.3k rpm / .13 hp unloaded

4.5x4 / 24.2k rpm / .20 hp static

5x3 / 23.8k rpm / .20 hp static

Apparent 149w is the engines top power rating.

Mr Cox

It also seems to peak around 24krpm with that setup. Perhaps some of Toads mods can help above that.

Pond Skipper

Yea from 25.5k down to 23.8 adding all three static readings you get an average of 24.5k still need to static test the 4.75x4 which may draw down the average a hair bit. The crank fit to case is still little tight perhaps I will fly this weekend and take in the pipe length another 1/3 in.

Pond Skipper

The CY06 came in its was listed as a 1.14 cc engine typical construction with a bronze connecting rod and no turbo head. Standard crank shaft, in summary this is not upgraded like the .07 that has an aluminum con rod with bronze bushings and the larger crank. The Sportwerks aluminum head fits and the other parts are fitting just fine no issues. Shown with a OS 10 to .15 size carb from the 90's and AP .061 Spinner.
160 deg. exhaust timing.


Also note this one has two long large intake ports and a more typical size boost port. Those intake ports will surely trump the older designs I have inspected.

The .07 has half that length as an example. The .06 should really ramp up with the OS carb

Pond Skipper

The stock back plate was begging to be trimmed up and taken advantage of. The legs are already tapped for 2.5mm bolts only needing the additional webbing removed.

The existing large hole for the pull starter crank pin access needs to plugged so I tapped it for a threaded 4mm bolt if using the muffler shown.

For use with a tuned pipe the pressure fitting shown will require a line restrictor to reduce 80% of the pressure. The upswing by using a 90 deg. fitting facing down I will have easy access to pull the pressure line off the engine during fill up to avoid flooding the engine. The legs are 4.5mm thick making them plenty strong for its secondary job with rubber isolation engine mounts.The bolts for the back plate to the engine need to be 2.5x8 to reach as much thread on the engine case as possible.

Mr Cox

Will you simply remove the pull starter axis? Wont that give you a large useless void behind the crank web?

I haven't tried to convert any engines with the pull-start, only the ones without it, but it seems better to grind of the extra pin from the stock crank and make a new backplate? I think the crankcase pressure (and the "compression ratio" of the crankcase) is very important for the scavenging, and any dead volume in the crankcase should be minimised.

Pond Skipper

Good point Kris,

The Mecoa back plates fill this void up with a small channel to allow the extended pin to spin.

My Sportswerk .06 engine has the pin removed and a typical all flat back plate.
The heat generated from grinding off the pin will require using water or oil in the process, done in small steps cooling
as you go would be best.

To solve the issue with this current back plate an easy fix wold be:
- scratch in some heavy grooves on the inside of the back plate.
- run a length of greased 28 to 30 gage magnet wire through the pressure nipple and back plate
- fill in the void with JB Weld.
- after a few minutes of set up time start to slowly pulling thru a bit of the greased wire every minute or so till the JB Weld is stable.

Another way is to make an aluminum plug. Can tap it in the center for some threads to hold it in place with a short bolt or with
a pressure nipple that has enough threads to reach in and lock down the plug.

aspeed

I decided to machine a new backplate when I did my little Picco. Rubber mounts normally lose a bit of power. A very solid mount gives the best performance. Having said that, it is ok, and better for the electrics.

Pond Skipper

Yes soft rubber mounts can equal rpm loss and
a bit of added weight / removing the engines mounting
beams will help a hair bit and give a clean look.

On the plus side:

- stand off to access the pressure nipple
- absorbs shock to the engine in a crash
- looks cool when your in idle mode
- reduces noise to the air frame
- helps to keep glue joints strong over time
- reduces vibrations to the fuel tank
- and RX , servos and battery welds
- helps to reduce the overall broken prop count
- reduces oil transfer to the fuselage
- aids to keep bolts,screws and nuts tight

Additionally:
- is different and so gathers interest / conversation
- tends to be photogenic
- some folks will think you know a thing or two

Pond Skipper

Alan has your Picco crank held up thus far?
I have seen about 20% reporting breaks from those who expressed using them.

Here is the stock back plate of the Vertigo .07 the void is better filled up the extended
pin has not been ground off. Tapped threads for a hex bolt to seal the hole backed up
with a lock nut on the back side. I have ordered another small pressure nipple for the
second pipe.

aspeed

So far it has held up great. I have been afraid to run it until I do something about the crank. It may last forever that way. I have been thinking of an internal sleeve as you were saying, and then giving a bell mouth to the outlet of the crank hole like the little Fora does.

Pond Skipper

Yea in fear of breaking I want to make some effort even if its a loss in performance so be it I bought a spare just in case.
Note the Picco already has what they call a turbo crank (wave channel) exiting the crank hole.

Finished weight with the firewall mount:

Pond Skipper

Welp ready to go back to building the Skorch II.
I have exhausted the small engine car conversions with two more spare .07's and a Picco left unchanged.

As shown:
.05 Fuji / .06 Sportwerks / .052 Picco / CY06 / .07 Vertigo

Pond Skipper

I ran up the CY06 today curious how the void in the back plate would effect idle etc.

Note I used the APC power charts:

Nice smooth running engine idles fine using a 4.75x4
I put the Fuji muffler on it with its pressure tap best
it could make was 62w. Looks like the extra volume
in the back plate needs to be filled up to help increase
power. After break in the CY06 does not have as much
compression as the other engines.

So I put a Mecoa back plate on to see if that would
help improve performance. Compression was about
the same, power increased to 77.6w. The Fuji muffler
keeps the engine quite so I took it off and added 9in
straight pipe power went up to 81.47w
Stock china plug might fair bit better with a quality hot plug.
So top rpm with the 4.75x4 / 19.1K after 3oz of fuel

After clean up, after run oil and allowed time to cool down
some additional compression but only about 80% of
the other engines.


I plan to measure and compare to the .050's the piston as it seems like a .059
.
Will fabricate a stand off bracket for a remote NV and
test the .07 next with the Profi pipe.

Pond Skipper

Ok I have done a preliminary brief test on the Vertigo .07 this carb has a low end needle. I had to reset it and used a rubber band to hold idle then manually pushed the lever forward with a still in tacked finger while holding the engine in my left had. Sketchy way to test shame on me..

According to the APC power chart the engine made it to:
APC 5x3 / static
25,227 / .24hp / 179w /

Using the static thrust calculator:
18oz / 72 mph

This was without trying much effort as I wasn't happy trying to one hand the two needle settings and throttle so stopped plus the heat was building up with only a folded napkin between my fingers and the engine.

Was enough info to encourage me to mount the thing proper and continue the testing with the Profi pipe. Sounded
really nice on the pipe and the engine ran very smooth with a stock unbalanced prop.

Pond Skipper

APC 4.75x4 just hit 24,739k rpm / no pressure had to add about a half turn to feed the engine at this load.
14.5oz thrust / 94.6 mph / .225hp / 168w not bad for just running in the hand.
I imagine hitting 25k ish will be possible once I have it bolted down on pressure.



Note the NV arrangement is similar to the AP Hornet .09's a simple adaptation to the stock car carb
with a 90 deg 4mm threaded aluminum nipple, short section of thick walled fuel line and a OS .10 NV.
The two ends are not touching but very close to hold its position without the need of a stand off mount.
Fuel metering and draw was good and can be adapted to all those typical car engine carbs with forward
facing NV.