cox throttle

[edplane]

Heres an idea to make a cox throttle. :censored: I havent tryed this yet, so any thing can happen. cut a small strip of poly- propaline and remove the needle cap. ream a hole so the valve will fit thrugh. about a milimeater away, make a smaller hole for a push rod. trim the exess plastic. fit it so the rod stops on the needle when you push forward. when the engine is running, tune the needle to the slowest speed. put on the throttle so the rod is touching the needle. pulling it tward you incrses speed and vice versa.

[edplane]

Do you think this will work?

[on pipe]

From what I understand, your saying to make a plastic arm that fits on the needle valve to control it. I think the fine threads on the needle valve won't give you enough movement to go from idle to full throttle in the 120 or so degrees of movement you would get with a servo rod. Ross

[RocketMan09]

yeah, but at least it will throttle some, like a pulse jet or the muffler-throttled .049's

[TLyttle]

Personally, I have yet to see a needle throttle work well enough to bother with. Check out other sources for a Hiscott or Tarno (both long out of production for obvious reasons) throttle and you will be much better off.

[edplane]

Actualy, its about 180, not 120, but i think that it should have at least 10,000 rpm to 15-16,000 rpm, at least for slower flights and softer landings when you want to land now. I cant try this for myself right now; its too cold and my engine is in the shop. Its a compression problem. But, I need a throttle so i cand drop this cute, little bugger in a Aeronca 7ac Champion, if i can actually build it.:) I suck at building planes from scratch, but, with a little more experiance, this should be good.

[on pipe]

Actualy, its about 180, not 120, but i think that it should have at least 10,000 rpm to 15-16,000 rpm, at least for slower flights and softer landings when you want to land now. I cant try this for myself right now; its too cold and my engine is in the shop. Its a compression problem. But, I need a throttle so i cand drop this cute, little bugger in a Aeronca 7ac Champion, if i can actually build it.:) I suck at building planes from scratch, but, with a little more experiance, this should be good.

Actually if you hook a servo up to a receiver, you will see the arm does not go 180. Closer to my 120. Even if it went the full half-circle the servo rod would hit the pivot point. (of the servo OR the needle) Anyway you sound like you have it figured out so go for it! :confused: Ross

[edplane]

I will. And i guess your right, but when i moved it by hand it easly turned almost all the way... exept if it went back further it could move all the way around. I hope this works... exhast throttles are hard to come by!:)

[boberos]

Cox Throttle,
Does not get much simpler than this.

http://www.rcuniverse.com/forum/m_6932958/anchors_6932958/mpage_1/key_laumer/anchor/tm.htm#6932958

[boberos]

Edplane,
Here ias another one.

http://www.rcuniverse.com/forum/m_2874106/mpage_1/key_quick%2Cdirty%2Cthrottle/tm.htm

[edplane]

Mabu i will try that..if i can get my engine fixed, the parts and some wrmer weather.:)

[david.ingham]

As I wrote somewhere before, I had very good speed control with the needle on a Tee Dee with a Black Widow cylinder. The TD needs a lot of sub-induction because it has a venturi type carburetter, instead of a choke type like the reedies, so it rapidly becomes richer with RPM. So with no sub-induction it runs at constant rpm, more constant than other engines or motors without governors. I can't remember how many turns it takes to control it. Maybe a string or belt wound around a spool or sprocket is needed.
It would waste a lot of fuel when running slow.

[edplane]

i hope i can get this to work soon.

[edplane]

Could someone try this out so i can deturmine where the throttle servo will go in mu plane?

[edplane]

Anyone?

[edplane]

ill try today if its nice out:):(:):):(:):(;p;p

[edplane]

Ok..so i tried to start it but now i think my fuel is bad from sitting around. Now where can i find like $30 for a gallon of fuel?! :) :)

[Andrew0820]

If your fuel was good a couple of weeks ago and has been tightly capped since, it won't be bad. Sealed fuel, kept cool and out of direct sunlight, has a pretty long shelf life.

[edplane]

If your fuel was good a couple of weeks ago and has been tightly capped since, it won't be bad. Sealed fuel, kept cool and out of direct sunlight, has a pretty long shelf life.
I know that, But i used a lot of it on 'different uses', which i dont want to talk about.
And i pretty mutch had the fuel for as long as the engine;about a year.

[propjobbill]

I have a couple of videos plus a post on RC Universe about a simple throtle for cox Sure start engines. I use a plate to go over the choke tub. I run it on a modified SS and get from about 5,500 = 17,000 rpm. I am still working on this design on the one video you can see a small hole in the plate. When closed the engine idles at about 5,500= 6,500 rpm depending on engine run when the plate is pulled full bach so the hole doesn't allow air bleed into the choke tube the engine will die. Here is a link to the videos.

When the weather gets better I plan on making some better videos outside with better details.

You can also check out my post at RCU giving details on my first version of the throttle http://www.rcuniverse.com/forum/m_6867312/anchors_6872590/mpage_1/key_/anchor/tm.htm#6872590

http://www.youtube.com/watch?v=h91V-rSV1AU&feature=related
http://www.youtube.com/profile?user=propjobbill
http://www.youtube.com/watch?v=KKXThGEl_FE

[edplane]

thats basucly the same thing im talking about, only with a peice of metal

[edplane]

1st is at idel and second full throttle. the servo is hs-55, and the stops are broke so it can move 360. I need a new top case . this is a power pack for my aeronca 7ac.

[propjobbill]

Once you start running the engine you will notice it has very little effect until the choke tube is well over 1/2 closed, more like 2/3 closed before you begin to see any difference. With a 1/16" gap it will still run at about 10,000 rpm.

[edplane]

sorry.. i acendently put the pushrod on the wrong arm, so it doesent work right. As said in the cox trobleshootind and oporation guide, 1/2 a turn should decrese a shrill whine to a cracling burble, so this should work.

[propjobbill]

Hope it works for you, but I have found lots of things work on paper but real life is a different story. post your results after you test it. Maybe I've been taking the wrong aproach

[E-Challenged]

You can probably scare up a Cox .051 or .09 R/C engine on Ebay with a decent throttle that actually works. Cylinder sleeves , that nearly cut off exhaust, reduce rpm's, but don't idle nearly as well as a properly designed throttle. Ya know what works a lot better and more reliable, an electric motor with speed control! And you don't have to try and find expensive glow heads.

[Jason_WI]

I am going to turn a throttle on my lathe tonight for the 5 Cox sure starts that I bought this week. I am also going to turn some spinners too. Just need to find longer 5-40 screws fror the spinners and prop.

Jason

[Andrew0820]

Just need to find longer 5-40 screws fror the spinners and prop.



I replace the slotted screws with socket head screws -- they are less prone to strip and easier to tighten.

Microfasteners (http://www.microfasteners.com/catalog/products/SSCSCA.cfm)

McMaster-Carr (www.mcmaster.com) -- search term: socket head screws . They carry multiple lengths and alloys.

[Jason_WI]

Here is my version of a throttle for the surestart engines. The surestart choke tube is tapered so I used a .250" reamer to a depth of .625". The reamer leaves a smooth and accurate surface. I then turned a piece of aluminum down to .248" and parted it off at .625" long on my lathe. I then bored the throttle body using a 3/16" drill to a depth of about .4". The other end was drilled and tapped to 4-40 thread. I cut a grove in the throttle body for a o-ring but it turnes out that it is not needed. I then placed the throttle body in the choke tube and drilled a 1/8" hole through both. I used a 4-40 screw to mount a futaba servo arm to the top. I haven't taken any tach measurements yet but it works great and can stop the engine by closing the throttle all the way.

[Mr.Me]

here's my throttle, i'll hopefully run it tomorrow so we'll see how it works.

[edplane]

Hay, Jason, Thats a nice throttle! I use a pencil to start my engine, and i stick the tip in the end of the snorkle and get nice throttle. How did you make it?
And mr me, I dont get exactly how yours works. How is it?
I was going to try starting my Cox today, because i got more compression after oiling it.
Its too cold today.:)

Eddy

[Mr.Me]

the metal plate just moves over the tube just like yours does. i might as well just go run it now, i have nothing to do and there's no school today.i dunno might also take a nap.

Regards,

Nick.

[edplane]

wait, so it works by cutting off air to the engine? Mine works by changing mixture.

[Mr.Me]

yours is turning the needle valve? that ain't gonna work very well... mine works like a carb.

Regards,

Nick.