tangerine-jack

Hey all! I’ve been following the forum for a while and decided that it’s time I jumped into the fray. I can’t think of a better way to do that than by having a problem.

First a little background. I have been in RC on and off for about 25 years now, so I don’t consider myself a “beginner” but I am far from being an expert. I have been out of the flying loop for about 14 years and I have recently got back into flying. I’ve noticed a significant change in technology, so bear with me as most of my knowledge and equipment is quite antique. I own a World Trainer 40, much beloved and quite bashed around, but a real trooper, and I just got done scratch building a Morane-Saulnier Model H monoplane (40” span for 3 channel) and I have a Voisin 1911 Canard plans on the table now and I will be starting on that soon. I used to fly 1/2A 2 channel quite a lot as I really like how easy and relaxing they are to fly, as well as the versatility in transporting and flying out of small fields.

OK, now that brings me to my issue. On the Morane-Saulnier I installed my Cox Medallion .09 R/C with the rotating throttle sleeve around the cylinder. I’ve modified the needle valve with a fuel line sleeve to eliminate air leakage, but otherwise it’s stock. I’ve had the engine since maybe 1986 but have never flown it before. The problem, or perceived problem, it that even with the throttle completely covering the cylinder ports, the idle speed remains nearly the same. From completely closed to wide open I estimate a 300-400 rpm change, hardly what I would call a “throttle”. So the question is, is this normal? Is there a modification to make the throttle slide more effective? Should I junk the engine (which I’d rather not do as it does run very well)? And finally as a red herring- what is the optimum prop to use for this application?

I don’t want to take my new plane into the sky without some form of engine control, as I see it what would be the point of 3 channels then anyway?

I posted this also in the questions and answer forum, but I thought I might get a better response over here. Thanks in advance!

skaliwag

My Feedback: (1)

Weeel .. there is nothing wrong with your engine, the problem lies with the fit or lack of it at the ring to cylinder. Your not going to get a replacement from Cox, they won't have any.
When they did these they did it the olde fashion way, they ground the cylinder to fit the ring. There is someone else on the forum looking for the same T/Ring.
The 1.5cc MVVS carborator can be modified to fit this engine. Andy W. did one for me.

Very nice airplane too. Where did you get the wheels?

tangerine-jack

Thanks for the advice. Your explanation has a lot of merit, I suspected that air was getting in somehow, but I still don’t see how the thing is running nicely with the ports completely closed, that is quite a bit of air leakage from the ring to affect the RPMs so little. The throttle ring does not have very much slop in it, I only see a very minimal lateral movement, seems to me just about enough to compensate for heat expansion. In any event, is there a cure for this that can utilize the original parts, if not, where do I get a carb replacement?

The wheels were an impulse buy at the LHS, I think they are made by Sullivan, but I threw away the package. Next time I’m there I’ll get the info.

Thanks for the compliment on the plane. Interesting story that one is. About 1981 or so I wanted an RC airplane, but didn’t have the money to buy a kit, so I ordered a set of planes for the Morane-Saulnier thinking to scratch build. In retrospect it probably wasn’t the best first scratch project (let alone a first RC plane), mid wing and under cambered. In any event, I built it, rigged it for 2 channels with a Cox TD .051 and it flew, but met an untimely demise in sometime around 1985. Since that time I’ve been through many planes and moved many times and the Morane slowly faded from memory. A few weeks ago I was cleaning out the bookcase when lo and behold; I found the plans for the Morane. I didn’t think I still had them! Anyway, I thought that it would be interesting to rebuild the aircraft using what skills and tricks I’ve learned over the last 25 years.

Construction began about 3 weeks ago using the much yellowed and slightly torn plans from 1981. The first thing I found out was that not a lot of hobby stores carry balsa wood anymore. I think the ARF revolution has something to do with that. When I asked for the sheet balsa and explained I was scratch building an airplane, most clerks at the hobby shops looked at me like I had a squid on my head. Evidently nobody builds, but just buys and ARF and flies, or at the extreme, buys a kit. I'm not that way, I LIKE to build, and I like to build odd aircraft. I did end up finding a great hobby store very close to the house, spent about $40 on wood and sundries, and began to cut some balsa. As I worked through the project it became clear to me that my first attempt not only should not have flown, but should have folded up in mid flight! I certainly made some mistakes and took some very dangerous shortcuts back then! I have reduced the size of the tail feathers slightly to give it more of a scale appearance, installed the correct bent wire landing gear struts (I believe I just used 2 wires and some rubber wheels on the first version but I don’t really remember truth to be told) and made a steerable tail skid.

Through the magic of photo copier and wing jig, I now have a very straight, very strong little airplane that I can’t wait to fly. BTW, the pilot on the plane now is the same one I had on the original airframe. I have a few details left to do before it’s ready for the air, such as number markings and flying wires, etc. I’ll be very interested in seeing how this new version flies compared to the original. I remember the plane having a very high climb rate (that I like) and a slow and lazy turn radius (don’t like anymore), when the engine cut out (it had no throttle), it took a very nose down attitude and I flew it in with up elevator.

It should fly better now, if not then it will make a spectacular impact and I’ll know that the design is a dog. I buy, I build, I fly, I crash, I buy, I build, I fly, I crash I buy, I build, I fly, I crash I buy, I build, I fly, I crash I buy, I build, I fly, I crash.

combatpigg

My Feedback: (3)

If you figure you have nothing to lose, JB WELD a .061 carb on it. The problem then becomes getting even running without the benefit of muffler pressure. So then you are back to square one and would save quite a bit of tinkering with a Norvel .074.

skaliwag

My Feedback: (1)

Instead of JB way if you can find a TD 09 carb body there is enough meat on the barrel of an AP 061 carb to thread it and screw it in. The thread on the .09 is the common all aeromodeller's garden size of 1/4 X 32. The problem is that you need a 1/4 X 32 X 1/8 Jam nut to lock it there, as Cox themselves did with their TD 09 and 051.

I have adapted the AP carb and used glow plug washers to get it in the right place when snugged up. Be carfull not to over tighten.... there are no more .09 carb bodies in the Cox cage.

If you choose to go the "glue" route, ATV works better, it is some what removable.

combatpigg

My Feedback: (3)

Sounds like the same thing could be done to a TD .049, isn't that the same thread? Again, the throttleability without any muffler pressure is the question, too.

DICKEYBIRD

A buddy of mine had a Medallion .09 R/C on a little biplane and it throttled very well with it's exhaust throttle sleeve. He used a 7x4 Master Airscrew if memory serves.

It seems odd that yours only slows down 300-400 rpm. Have you run it on the bench with a manual linkage to make sure the throttle sleeve is closing all the way? If the sleeve fits without a lot of slop, it has to slow things down more than that. You may have a servo/linkage/installation problem due to vibration with the engine installed in the plane.

My little modified Tee Dee .049's have a range of 4500 to 18,500 rpm using only an exhaust throttle sleeve. Seems like an .09 should do similarly well, less on the top end. Carbs, in general, don't work too well on Coxes....unless you're Andy Woitowicz.

If, in fact, your sleeve does fit your cyl. too loosely, there's not a lot you can do with it. The only 2 options I know would be to find another piston/cyl/sleeve assy. or lean on a machinist friend to whittle you one. They're made from an easy machining steel called Ledloy. Although deceptively simple looking, they are a marvel of precise machining. Makes me VERY respectful of the tolerances Roy Cox & friends were able to achieve day in & day out with relatively simple machine tools.

tangerine-jack

Thanks for the responses, great info! I'm going to try to carefuly adjust the throttle sleeve and go around the engine and tighten everything up, maybe something is loose. I've never flown the engine, so even though it is 20 years old, it's still "new". I want to take the plane on its maiden flight this coming weekend, but I've got enough experience to know that it would survive about 8.2 seconds before a total existance failure if the engine isn't right.

Dickybird, I'm certain the linkage is OK, but I'll check again anyway. I'm not the sharpest tool in the shed, but I know that an engine won't run when either the air is cut off or the exhaust is completly stopped. I fully agree that I should be getting at least a 10,000 rpm control band with just the sleeve. It is a mystery, but Cox engines are ruggedly simple things so I feel sure the solution is simple as well, I'm just to dumb to find it on my own. I really like this engine so far, it starts super easy and seems to have gobs of power, I wonder why they ever stopped making them?

rrragmanliam

My Feedback: (1)

Yep so do many of us. I guess the bottom line was the bottom line. Probably just not selling enough of the cox products to make it worthwhile. It's kind of sad to watch this part of modeling history slipping away into the histoy books.

Darren

tangerine-jack

Ah, the sweet ear numbing buzz of success! [sm=thumbup.gif]

Here is what I did:

1. Tightened the cylinder and head (they were a little loose)
2. Tightened the back plate
3. Adjusted the throttle so at idle the ports were completely covered + 1/16th of an inch, and at WOT they were uncovered
4. Started the engine at WOT. After the engine started I throttled back and the engine assumed a nice smooth idle at maybe 3-4,000 rpm.
5. Adjusted the servo rate to the lowest setting.

I can now start, taxi and take off (hopefully) with complete throttle control. I noticed that from idle to WOT is only 1/8” or so movement on the cylinder sleeve. I guess I was jamming open the throttle like I do with my OS Max .40 and was blowing right past the narrow operating range of the Cox, as well as not having the throttle sleeve closed enough to maintain a smooth idle. By setting the servo rate to its lowest setting I can now use just over ½ my throttle stick, good enough for me!

Tomorrow, oh yes, tomorrow we will see………………………….

flyinrog

My Feedback: (1)

That is a beautiful plane!, I guess no one mentioned the small amount of throw you need to go from idle to full throttle, almost like an on/off switch more than a throttle, I just got one of these .09's and have no idea what I can put it on....Rog

Remby

My Feedback: (3)

I put up a thread about parts and the quality of different dates they were built, and I feel it is about the part tooling.

The .09 spray bar is the trouble, as far as I can find. The tooling got so bad in the later issues , somtimes they would stop holding a needle by "thread jumping", even pop right out after say 50 or so flights.

You can check this yourself. Take your Cox Medallion (.049-.051/.09), and turn the needle out say 6 turns or so to the start position. Now, place your finger on the end of the needle, and carefully push it in to the spray bar , looking for slop. The one you have should show very little slop, perhaps none at all. I have a "new" (unused) one that has close to a 1/32" of slop, perhaps a bit more. Doubt it will last 50 flights, and as it wears, the brass gets thrown off ,right into the engine, not a good picture.

ptulmer

My Feedback: (5)

Lack of innovation killed Cox. The used market was HUGE and without new models, they had to compete with ebay. They didn't even try. TD 049's were selling for eighty bucks at Tower and the Wasp .061 w/throttle was half that. Estes probably never ran a single machine to make those engines. They seemed to be assembling from parts the whole time.

hollerp89

I need a throttle for .09 madellion cox engine#2901 is the number. instructions wouldbe helpfull tothank you bob .

build light

tangerine-jack, Off topic I was wondering if you could share with me How you made the cowl for this plane. It seems to be a beer or pop can yet it has these wonderful pleats in it. How did you do this?

Robert

tangerine-jack

I would be more than happy to share the technique of making corrugated metal. It’s so simple I’m surprised everybody hasn’t already stumbled upon it. I’m not sure what applications this can have in the RC airplane world apart from detailing some WWI aircraft, but here it is.

Materials:
1. Soda can. Beer cans will work, but they are thicker and harder to work with
2. Scissors
3. Paper crimper tool. I got mine from Michael’s, but any arts and crafts store will have them.

Process:
1. Cut top and bottom off of the can. Save for the aluminum recycler
2. Trim any rough edges from the aluminum sheet
3. Roll through the crimper using a back and forth motion

That’s it. It also works for any other thin malleable metal like copper flashing.

ptulmer

My Feedback: (5)

You know, I can't think of a reason in the world to do that to paper.[sm=lol.gif] This idea is easily as good as the alcohol stove idea.
(when it comes to recycling drink cans)

build light

Now that sir, is quite a nice trick! Do the crimpers come in more styles like the pinking shears do?

Quote by ptulmer:
"You know, I can't think of a reason in the world to do that to paper."

Ain't that the truth?

Robert

tangerine-jack

Paper crimping is used for making scrapbooks and other paper related hobbies. Evidently it's quite popular to justify Fiskar making a tool for crimping paper. I really don't know if it comes in other patterns, I've never looked. Next time I'm at the arts and crafts store I'll check it out. I think my next project will be a Junkers C.I or CLI monoplane both from 1918, they were both constructed from corregated aluminum.

hollerp89

i need parts for cox engines an not ebay . an mvvs .09 throttle valve kit.
thanks bob

skaliwag

My Feedback: (1)

The small MVVS is hard to come by these days, unless Ed Carlson has them.....

http://www.carlsonengineimports.net/index.shtml

However the AP.09 throttle can be adapted. You need to thread the stem, I believe it's 1/4 X 32 and use glow plug washers to shim it to get it in the right position cross ways. 1/4 X 32 jam nuts that Cox used are even harder to find. Unfortunately the AP unit does not have an Air Bleed like the MVVS but it does work.

hollerp89

SKALIWAG , THANK YOU
NOW WHAT SIZE PROP DO I USE FOR COX .09 ENGINE THANKS AGAIN HOLLERP89

hollerp89

[&o] well slaliwag i got my ap carb now how do i put it on my cox engine? i really dont understand how to to do it . please help? bob

skaliwag

My Feedback: (1)

You have to thread it 1/4 x 32 and shim it with Glow Plug washers so it is east west or find a 1/4 X 32 Jam nut that is at least 3/32nds thick.

hollerp89

well the problom with the ap carb ,on the cox .09 how do i get the peace off the end of the shaft where prop fits on. if you know please let me know .