Pee Wee Horseshoe back plate

Great run with rpm-s above 16k

Nice steady run. Didn't miss a beat or lean out at the end.

No it’s just the TD .020 venturi and NVA. The crankcase to crankshaft fit is loose on this engine. it’s a nose bleeder. Might be a source of the air leak and varying RPM throught the run. This was the second run in the video. I added fuel tubing to the needle valve to act as a seal since the first run varied in RPM also. As you can see it didn’t help.

Here’s the same short block but on a freshly printed horseshoe backplate and fine thread NVA.

Same surging with this backplate. Runs better at 3 minutes in. Wonder if it’s because the exhaust port opening faces the prop on this engine?

Looks great Jason. Bringing life back to some engines that otherwise would not have one. It is times like this that I wish I had a 3D printer as well as the knowledge to design a backplate for my crankcase and p/c. While here, is the lower row furthest left the newest one using the new nozzle? Just curious as it 'appears' to be a bit smoother than the rest (not that it really matters, just curious)? One day I may take a look at one, but as you made mention before, a decent one is fairly more than I would be allowed by the missus.....

Here is the backplate printed in natural DuPont Zytel. I printed this a while ago but never had a chance to run it. With the natural Zytel this leaves the option to dye these in different colors.




Forgot the run video.

16.9k to many holds at 17,118 rpm

This is scheduled to land at my door today I paid $21.79 in total just to rob the 128 tpi NV for the
other horseshoe back plate. Worth it to get a solid steady rpm setting. Want to try a pressure tap to
see just how far I can push the rpm. Will post a test vid when ready.

Anybody know where to get taps and button dies for the 128 TPI threads? I imagine #2 threads? Or the metric equivilant. The Fora .15 is around .35mm pitch. quite a bit coarser, and they use a bladder. Ya it is a much bigger motor, I know. Someone should make them again. I might even have to make a few at least for myself. My lathe is for production, but in the stone age. Won't the 80 TPI needles work?

Stock Pee Wee is tough to set the NV prone to air leaks so a mod has to be made.
Using a washer and a bit of silicone fuel line shows improvement. Max rpm tweak
is hard to get and hold.

I posted this 80TPI NVA results in the other thread. I’ll add it here to make your conclusion on 80TPI NVAs.

This first engine used a burred cylinder and piston set. I deburred the cylinder and removed some rust. Found a crankcase, crank, and drive washer. Added a starter spring and new glow plug. Assembled the backplate with a short 80 TPI needle valve from a product engine.

Using a black 4.5x2 prop and 25% Cox super power fuel it started right up with 4 turns open on the NVA. Took about 1/2 turn to find the sweet spot. Ran pretty well. Had to adjust the syringe up when the fuel was getting lower.



It’s about an 8 minute run.

The second engine used an existing .020 short block. I assembled the backplate with a long 80 TPI NVA from a SureStart engine.

I think the longer needle valve vibrating caused the varying RPM. It’s not bad though.

Same prop and fuel as the first run.



Here are a few pictures of the assembled engines.

Looks like about 1/8 turn leeway. I have a .15 size F2D plane with a bladder that has about 1/50 th of a turn leeway. It is ok, because it has the lock nut so there is no slop, and a bent end. This looks ok with the 80 TPI. As mentioned maybe some silicon tubing with a washer, and a shorter needle. This one doesn't seem to leak, just the slop changes the setting every time you move your hand. Is that a 2 oz syringe?

Not sure on the volume of the syringe. It doesn’t have any graduations on it. Guessing it might be 20-30 ml.

The needle valve has the black seal installed to help with air leaks. Silicone tubing added certainly couldn’t hurt.

10 minutes an oz. make it a cheap date.

Mission accomplished the donor part came in the mail. This one has
a pressure tap for solid fuel flow. Will bench it this weekend. Not
sure which prop I will use, this one is too bulky for the Wee Wizzer
shown with a APC 4.2x4N The TD High Compression head makes
less compression with 1 shim then the Kamtechnik prototype.

I expect some loss in rpm and hope to gain some back with the
pressure tap. The manifold header is a prototype and has done
well testing with a TD. Fingers crossed Greg moves forward with
these. They require one last tweak a bit more volume around
the manifold to improve breathing. This piston cylinder set was
picked as the SPI is less than normal. One port has 40% exposer
to the header.



Good weight with a .010 bullet spinner matches the smaller Pee Wee thrust plate well, shown with a HQ carbon blend 4x4.5

That header looks pretty cool. I wonder if the CF Zytel could handle that heat.

Worth a shot, I hope that it will work!
The oil spray may help it stay cool enough.
Note it uses a O ring on the top side seat,
gives just enough buffer room for variance
per each cylinder to maintain a good seal
and keep it from rotating. A round header
would allow add on's such as exhaust diverter.

If the header works maybe a printed tuned pipe

Whoa that would be the ticket little Pee Wizzer with a tuned pipe Killer Pee Wee fo shizzle!

Here are some size comparisions using the Profi pipe reduced to fit the .020
The wall thicknesses would have to be more all reference to aluminum in the pics.


This pic narrows it down to the suitable proportions, a
TD .020 has been tested in the air best pass 37,304 rpm /106 mph all carbon 3x3 prop.
Best prop for this engine after many tests 3.7 x 4.5N / 120 mph.
Max length should not exceed 8" based on the known capacity for rpm of a .020.
Peak should be 29k - 33k for best prop match for either thrust or speed or a mix of each.

I think the diameters should be smaller for the .020, (and .010), but the length should still be the same as the Profi. The rpm and wavelength is around the same.

Tested the new build with header and a stock HQ carbon 4 x 4.5
With a bit of back cut on the prop the engine can spin a 4x4.5N
with more thrust / pitch speed. For now I wanted to see what it
can do with a stock prop. The engine is using a piston from a
vintage thin walled cylinder and a modern cylinder ran it rich
for a few minutes then worked on the NV. Due to 4.5 pitch this
is a good bit of load on the engine.



Oct 5, 2019
Cox Pee Wee with pressure tap!
17,603 rpm / HQ 4x4.5 / 75 mph pitch speed
3.52 oz thrust / .045hp - 33w / 25% nitro
Pitch speed is great for a Pee Wee! The NV
was tweaked just enough to keep it steady
I want to baby the new piston / cylinder as
they are from two different era's.
Peak 17,684 rpm should make a bit more
after a few more runs.

The engine kept clean no oil drip the header
did it's job directing all the spray to the side.
Turbo plug would have made another 1k ish.
Compression was weak after the run. This
setup would be good for CL or RC where goo
control is desired to protect the airframe from
long term damaged and quick clean up between
runs. Noise factor was isolated to the header
it was a treat to run this engine!