049 reed valve venturi throttle

That's a pretty cool muffler, nice work.
My shockwave crashed about the time you were trying to tell the wife what you were doing.  I'm making a Movie, honey!

Gotta go. I'll come back this evening and watch the whole thing. Finally somebody besides me that narrates their videos. 

Rusty

That is food for thought, I must try that out. Very neat slow running.

Do you turn down the voltage to avoid burning the plug out?

very cool,i just might have to see if i can do that,do you have any close up photos of the building process  

will it run without the glow head clip hooked up?

I got one of the Ace throttles in a lot of engine parts a while back, was going to sell it but my cat ripped the bag all up.
The parts are all there, if anyone can use it Ill send it for cost of postage.

The throttle is off to bullit123, but more are hidden on eBay in a parts lot.

Forgive me for asking the question I did in my first post. I didn't watch all of your video before yapping. 2,900 RPM is darn impressive!

KP

RknRusty wrote:That's a pretty cool muffler, nice work.
My shockwave crashed about the time you were trying to tell the wife what you were doing.  I'm making a Movie, honey!

Gotta go. I'll come back this evening and watch the whole thing. Finally somebody besides me that narrates their videos. 

Rusty

Thanks Rusty. Yes... even "with" the muffler, she thought it was too loud.

BTW... the muffler consists of a pc. of aluminum tubing lg. enough (in i.d.) to fit over the glowhead (approx. 7/8") and about 3/8"L. with a 1/4" hole drilled in it's side. Through this side-hole, I installed a "header pipe" which is merely a .22cal. shell casing. The flange (flare) on the shell casing holds it in place on the inside. What holds it all together are 2 discs (2.5" in dia.) of bicycle tire inner-tube. I punched out 1/2" dia. holes in the centers of ea. and "stapled" the discs together 3/4 of the way around; leaving room for the "header pipe" to exit. The aluminum "ring" is then inserted/sandwiched (just "stretch it open" a little...) in between the two discs with the ring's side-hole aligned with where the discs "aren't" stapled (for the header pipe/shell casing to exit) Install the header pipe from the inside and you have a muffler/silencer, that "pushes right on" over the cylinder, without any engine disassembly... and does not impede needle valve adjustments. It's a "red neck" design... but it's cheap and effective. You can experiment with dif. sz./amt. of header pipes too.

Thanks for your interest Rusty!

ian1954 wrote:That is food for thought, I must try that out. Very neat slow running.

Do you turn down the voltage to avoid burning the plug out?

Hello Ian,

The glow driver was running in the "green" on the meter during the vid. I kept the "juice on" because I knew I'd be re-starting the engine while trying to reach a "consistent" low idle for the video.

The "instructions" that came with the Ace RC (p/n 630) reed valve engine throttle state; "A lower idle can be obtained by using a Cox or Tatone muffler which increases back pressure and holds the heat to the plug at low speeds better." I assume this to be correct; although I haven't tried either of those. I make my own mufflers which seem to work well with this throttle.

I have "bench-ran" this throttle/muffler set-up with a servo connected and without the glow driver connected... it put a smile on my face!

Thanks for your interest... and good luck!
Roger

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bullit132 wrote:very cool,i just might have to see if i can do that,do you have any close up photos of the building process  

Hello bullit,

    I don't have any photos/vids of how I fabricated my needles...  but I can shoot a photo of the Ace throttle kit parts/instructions if that helps. Although I went into detail on my orig. post on this topic, it's quite easy to make a needle. It's function is to simply meter fuel/air through the back of the venturi... and even a "crude" taper on the end of the 1/16" music wire will produce results.

    I should note that you need to use a Baby Bee/Golden Bee type engine with integral tank/metal backplate for this... NOT a prod. engine with plastic backplate. If you have both type engines and the "Bee" is worn out/for parts; you can swap it's tank/backplate to your prod. engine. I have several Cox "Bee's" and lots of parts. One of my backplates' venturi holes is smaller than the others... and the music wire won't fit "through it". Check yours before you try to do anything. This condition can still work though... you just need to grind the needles "taper" to fit. DON'T try drilling out the backplate... this could/will produce a "burr" where the fuel enters the venturi.

And don't forget... the use of a muffler is recommended for this application; to increase back pressure and keep the glowplug HOT at lower engine speeds.

Thanks for your interest,
Roger

looperdude wrote:will it run without the glow head clip hooked up?

Hello looperdude,

Yes... See my reply to "Ian" regarding your question. To expand on this; Use FRESH fuel and a muffler. I was using Sig Champion 25 fuel and a Cox grey 6 x 3 prop in the vid.

Thanks for your interest,
Roger

kpriddle wrote:Forgive me for asking the question I did in my first post.  I didn't watch all of your video before yapping.  2,900 RPM is darn impressive!

KP

Hello KP,

No worries!!! I've had that vid posted on YouTube for a year now, and not one comment there. Your comments are MORE than welcome!!!

When I first tried the throttle, I was amazed. There are others I've seen recently; for the prod. engines, but this approach appears to be the lightest as far as weight is concerned. With the new generation "nano" servos and LiFe receiver packs; it's now possible to build a nice little half-A "throttled" R.O.G. gas plane for RC.

"Thanks" for your interest,
Roger

Thanks much; to all of you who showed interest in this topic! I appreciate it very much. YouTube wasn't showing me any "love" LOL

A note worth mentioning... As I stated in the orig. post; The only modification to the engine is the removal of the tiny mesh screen on the backplate. This is for "Bee" type metal backplates only... NOT the plastic one's used on prod. engines. Also; the screen is there for a reason... to keep dirt out. Removing it makes the venturi vulnerable to dirt entering... which you DON'T want. A pc. of even the tiniest grit between the reed and seat will cause erratic engine operation. To prevent this; a small pc. (1" sq.) of polyurethane "air conditioner filter" mat'l. is placed between the engine and firewall. The polyurethane is impervious to glow fuel, and the needle will pass right through it.
I also use this filter mat'l. as a "cushion" for my wedge style fuel tanks when flying C/L, to prevent "fuel foaming" from vibration.

Finally... a "muffler" of some sort (I make my own) is recommended for this type of throttle; to produce back pressure and hold heat to the glow plug at lower engine speeds.

Roger

PM sent to crankbndr for the throttle system.

Shawn

sdjjadk wrote:PM sent to crankbndr for the throttle system.

Shawn

Shawn, if you can't find the Ace kit on ebay (I believe that "CrankBender's" orig. Ace kit went to member "Bullit 132")  you can simply "make" the needle... You need a pc. of .062" dia. (1/16") hard music wire; which "is" the main component... cut to about 1-1/4"L. "Taper" one end; from about a 1/4 of an inch from the end... down to 1/2 the dia. (.031") "at" the end; by "chucking" in an elec. drill and "pinching" the exposed end of the wire with fine sandpaper; while running the drill. (use gloves or pliers... it will take a while... and it WILL get HOT!) or run a belt sander/D.A. sander/grinding wheel; while running the drill at a slight angle to the face of the abrasive. A "consistent smooth taper" is desired... BUT... even a "crude" taper will produce results in throttle transition.

I measured the needle that comes in the orig. Ace kit, with a precision vernier caliper... The needle is made from .062" dia. music wire... is 1.187"( 1-3/16") long... has a 1/4"L. taper... and is .031" (1/32") at it's "rounded blunt" point. Shoot for "close" to these dimensions if you make a needle.

When the needle slides into the backplate's venturi hole "past the taper"... it will completely restrict the venturi hole and stop the engine quickly, from lack of air... therefore; you can set a throttle servos' "trim" to adjust for this point. You can set a "low idle speed" of whatever low rpm# you can "consistently" achieve; using a muffler... and then "trim" the servo (i.e. after landing) to stop the engine.

Linking to a servo is achieved by using a short length (5/8") of sm. silicone fuel tubing placed over the needles' other "un-tapered" end... (a drop of solder on this end of the needle, is a good idea to hold the fuel tubing in place). Connect the other end of the fuel tubing to a clevis; with a 3/4"L. pc. of 2-56 threaded rod; CA glued into the clevis, to keep it from turning "in" or "out" from vibration. You want "zero-slop" in this connection... and you don't want the fuel tubing to "slip"... yet... with this arrangement; it can be "fine-tuned" for length-of-travel; by gently pulling/pushing either; the "needle" or the "threaded rod" in or out of the fuel tubing; which acts as a "flexible" coupling. (Ace RC supplied/recommended the "fuel tubing coupling" in their kit)

One further note: This throttle concept was primarily designed for 1/2-A RC ships; utilizing a "built-up" fuselage and a dedicated throttle servo. A little experimentation could produce a C/L 3-line "carrier" model; by designing the proper firewall with space rearward for the needle/linkage to travel and placing a 1/16" wheel retainer/collar; as a "stop" on the needles' "shaft"... adjusted for slowest practical engine speed. The extreme "opposite direction of travel" (i.e. needle completely "out" of the back-plate/venturi opening) yields w.o.t. operation. A 3rd line, sm. 90 deg. bellcrank, and lightweight spring/linkage is all you need. "Fail-safe" it for w.o.t. where "pulling on the 3rd line" tensions the spring to slow the engines' speed.

A half-A Carrier model was built; using "Bernie's" throttle... on "Duke Johnson's" model... see this thread:

https://www.coxengineforum.com/t3865p20-throttle-backplate?highlight=throttle

If you have any questions whatsoever Shawn... I'll be glad to help you.

Roger

An old thread here... but I continue to mess around with this throttle design. During bench-tests; I'd been opening/closing the throttle manually. This makes it difficult to achieve a consistent low-idle speed.

The plunger-needle is made from 1/16" diameter music-wire with a taper ground on the end that enters the engine's air-intake. A 1/2A wheel-collar/retainer can be used as a "stop" to set a low idle-speed. A servo-saver can and should be used for a final installation in a model. That would be the simple way to set up this throttle. One could alternately omit the throttle-stop.. and use "trim-function" on the throttle-channel on their transmitter to further advance the plunger "in".. to kill the engine if they wanted.

Here's two examples using a spring-style wheel retainer.. and a set-screw type wheel-collar made for 1/16" diameter music-wire. (shown below; passing through the firewall of my jet-pump test fixture.)














I'll make a vid.. and post here to show the function soon.

Just a heads up that we have been stocking the "Ace" throttle since 2015: https://coxengines.ca/back-end/throttle-for-cox-049-engine-bee-style.html