combatpigg

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If I find there is a surplus of power, I'll restrict the intake, but right now I can't visualize having enough power for much more than extended glides.
Once the bigger props arrive, the real fun begins.

ratshooter

From what I have read the Wrights knew about dihedral but choose anhedral because they did not want a stable machine. They wanted a plane that had to be controlled at all times and would be more responsive to the controls. They did a great deal of testing and worked out formulas for the props, wing area and every aspect of their designs. They didn't just build something and hope it flies. I have seen some of the math they did and it was impressive.

There is a lot of information on the net about them plus a new book. You just have to do a little searching.

And no, the wings don't flatten out in flight.

ratshooter

Here is one read.

http://corescholar.libraries.wright....text=following

combatpigg

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That's a great [advertisement free] write up..!

combatpigg

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Here is a look at a balloon tank. A Sullivan tank stopper, length of ball point pen cartridge, a couple hunks of bamboo skewer to plug the spare holes in the stopper and Sullivan small fuel line..and a rubberband to secure a Nitrile glove finger to the stopper.I also show a CA applicator that I rigged as an "eyedropper" style of tank.
Since this twin prop / pulley is so hard to start, the eyedropper isn't practical.
The Slow Flyer props arrived. They are 8 x 4.5. They produce a ton of wind while cranking the engine with the electric starter.
At full size the engine just couldn't run them. The engine would pop-pop-pop, but there just isn't enough torque to have the engine take over from the starter. At 7 inches, I got the engine to run long enough to get a tach reading. 6300 rpm and a lot of thrust. Easily enough to fly this thing but the engine gets smoking hot. I tried adding head shims, but just made the situation worse. I chopped the props down to 6 inches but wasn't able to get the engine started.
The engine runs nicely with one of these props bolted directly to it, 6300 rpm but a lot of thrust. I'll make a point to try this combo on a lightly built model someday.

Mr Cox

It certainly looks great!
Regarding overheating it might get reduced a little once the planes moves in the air, but you could also try with a "Texaco" head, either OEM or the taller Merlin clamp with insert.

H5606

Thanks for sharing all the detail photos - that's great stuff! I don't know that much about the Texaco class engine but was wondering if the tall glow plug it was equipped with is a means to reduce compression to allow turning bigger props at low rpm and if this is a clue that would somehow help out or maybe a non-issue at this point. Perhaps a bunch of glow plug gaskets and a low compression head...

Duh! Just noticed previous post mentioned same and more I didn't know.

Pond Skipper

You could use larger dia. pulley wheels at the props for some reduction in load, or just clip the props down to 5in.

combatpigg

My Feedback: (3)

The tension that the belts exert on the crank, I thought would "cancel out", since there is equal pull in both directions. Not really, it might help with wear, but the engine is still seeing twice the load when it runs. The problem with getting the engine to continue firing after the starter is removed would be helped with a flywheel built-in to the crank pulley. A stubby prop could also be worked in to help cool the engine. Yes, the engine really needs a heat sink type head, too..!
The engine drives 1 belt / prop pretty easily, I'm impressed by how tough these O ring belts are.
Yes, it looks like larger prop pulleys would help the engine and I'll bet still provide ample thrust.
This plane is built twice as heavy as it should be. 1/8" Depron and 1/8" lumber would have been a better choice for the wings. The bamboo skewers are nice to work with, they would work fine with a more realistic build too..To install bamboo struts and braces I use a 1 foot long 1/8" drill bit to drill holes that have complex angles / routes from point A to point B.
Eventually, a more true to life [open] framework would be fun to tackle but I wouldn't want to spend too much time on a plane that's built to fly.
At least it was encouraging to see these Slow Fly props make this project look more feasible.

Pond Skipper

Larger wheels will have more grip on the O rings allowing you to back off the tension. Its a win win

combatpigg

My Feedback: (3)

The tension is set now with quite a lot of slippage [at the crank pulley] until the prop pulleys can catch up to the engine's speed. The belt occasionally bounces out of the groove now, so adding slack doesn't seem feasible unless I added some guides to keep the belt in the grooves. With larger prop pulleys, I might need to mount the props more inboard, though. Hope I left enough meat on the motor stick to do that.
If I lose a belt during flight, I'm pretty sure the model will cork screw right in.

Pond Skipper

Very true the old girl would spiral in at a fast clip with no chance to throttle down and save it. Yes larger wheel more grip less tension would be require to still get good transfer of power worth a shot if you can fab up the wheels. Where did you get the original fly wheels?

combatpigg

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I made the pulleys out of some AL round stock I had laying around. A better choice than aluminum might be nylon, especially if a slightly rough finish can be had...?
Today's project will be to try a MECOA head adapter and make a heat sink to clamp to the head.
Dieseling might work better, but I'm pretty sure it would dissolve the plane instantly.

combatpigg

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Minor update...
made a new drive pulley with more mass and slightly less belt speed [less diameter].
I also switched to a Norvel plug and did a "baseline" run right off the engine. It put out 6400 rpm with the 6.2 x 4.5 Slow Flyer prop and plenty-O-thrust. With both belts hooked up it starts easily now but the extra power is throwing belts now..............
Next project, make new prop pulleys with deeper grooves and more diameter to reduce rpm.
Also, the engine had a 2 second shaft run tonight after tossing both belts. The engine still feels good, but it's time to remove crankshaft end play.

combatpigg

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Another "non report"..just general ramblings related to this project. The Power Plant's R&D is on hold until I get a new lathe belt. I also ordered various sizes of O-ring drive belts to try.
As you can see I'm making new pulleys with deeper grooves and slightly different ratios. The original set had a 2.7:1 ratio and the new set has 3.5:1 for less prop speed, less rotational speed for the belts and hopefully easier running for the engine. I did get a chance to test the new drive pulley and the engine was easier to start. I repeated the test a few times and it looks like the extra mass helped. Or maybe the engine was just having an easier time with a pair of worn out belts..?
Unless you take a true scientific approach, it's easy to "buy into" an observation that is just a mirage.
I'm showing the picture of the rudder detail since it just occurred to me how "HOKEY" the Wrights had it rigged. It's a "Box Kite" that appears to be hinged at the 50% chord line. I guess I'll try to be faithful to this design and try it.
My best guess is that this model will fly at 20 mph...tops. Hopefully it's light enough to go that slow and be able to turn...
Hopefully it's controllable enough to survive a few hops. I think I'll slit the top wing near the tips and create some kind of a roll control to help the plane turn.

Pond Skipper

Bummer your lathe belt broke!!

With ratios in mind if a single reed engine can swing a 6x3 cox prop then the combination of drag weight of the drive line components and the extra prop would indeed take it well past 2:1. So 2.7:1 would seem reasonable if driving two 6x3 props.

I think your new ratio should get you in the sweet spot with the two 6x4.5 props. Should be a real treat and most interesting to see / hear the little wonder fly.

combatpigg

My Feedback: (3)

The sound effects aren't real impressive on the ground, but it does sound unusual. What you hear is a screaming engine that drowns out the props' noise and a little more mechanical clatter than with a direct drive prop. Hopefully, there is a surplus of thrust that will allow me to detune the power to a level that allows basic flight on a calm day.
This project has whetted my appetite to try other weird prop driven projects based on the lowly Cox Reedy. I can see the need for an electric starter fitted with a long snout to help get some crazy ideas going.

Pond Skipper

Look forward to seeing what you come up with.

I have thought about gearing up for more rpm using a small belt / O ring so I can face the engine forward.
If at 24k with a ratio of 1:1.6 would see 38.4k no prop. So with say a 3.5 x 4 perhaps 33k unloaded for 125 mph.

combatpigg

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I don't know how well overdrive systems work on engines that are already running maxxed out.
I can't imagine a belt being low enough drag [or sturdy enough] to provide a net gain.
With a gear drive if you could keep the external parts lubed that would seem to be your best chance but look at the weight gain and extra bulk involved.
With an .049 engine, look at how poorly a "tight" engine runs compared to one that has optimized clearances. By attaching external drives, you are creating a "tight" engine and sacrificing power...converting power into heat.
With underdrives, the losses can be offset somewhat. Look at how 20HP Model T trucks were used to haul tons of logs back in the day..!

Pond Skipper

I have used gears on a small outrigger hydro it was to gear down a TD.
Prop pitch for small aero engines suffer options for speed, there just isn't much of a selection.
Im doing ok with the 4.2x4 / AME Norvel to 28k but its still not enough rpm to bust the 120 mark , would need a 3.75 x 4.5 at 28k
I would have to custom cut if I could find a constant pitch prop cheap enough to hack up a handful for the plane with the right size
prop hub.

For less than 5 bucks you get 40 flight out of the belt before replacing no big deal.
You only need a hair bit of additional tension to seat the teeth. Smaller props should be easy on the set up.


Instead of pushing the engine past 28k or buying a expensive performance engine with bearings an option is to gear up and keep the engine peak the same as it was for DD. Gear to 38k and unload a 3.75 x 4 at 32k gets you 121.2 mph in theory

combatpigg

My Feedback: (3)

120 MPH is actually what most of my Cyclon .061 SWRs do with a 4.2 x 4..so that's a pretty ambitious target for a AME. I'm happy with the repeatable performance of the engine, it is happy too, so I've never wanted to look for more out of a different prop. If I could pull 5 more mph out of more prop, but force the engine to run hot..then no deal.
If you want to give over-driving a AME a try...it looks like you've got a great plan and I am the last person who would want to rain pessimism on a project like that..!
Let there never be heard a discouraging word...

Pond Skipper

Its an idea worth messing with at some point the sound of the high rpm prop should add some cool factor.
Lanky clean Thunder Bolt or Sky Kracker!

combatpigg

My Feedback: (3)

I am not any sort of a physicist, but it sounds like trying to get something from nothing. Now if you were trying to get a long stroke, low rpm diesel to deliver a higher power curve via creative gearing, I can sort of wrap my head around that.
Another way of looking at this is we have a screaming 2 stroke that runs at a relatively low efficiency [I forget the theoretic number] and by introducing more inefficiencies we hope to make the output of the "power system" more efficient.
Again...just thinking out loud.

rgburrill

Seriously? You have never heard of Gustave Whitehead? He flew the first powered airplane two years before the Wright Brothers but the US refused to recognize it because he was a German immigrant and that was not a good thing to be at that time.

Pond Skipper

Nope didnt say that just more RPM