Testors pipe bomb engine won't run

You probably didn't damage the reeds, the fact that you can't access them is more than likely the culprit. Chances are that in the two years they lay dormant they became choked in castor goo.

I have little experience with pipe bombs, others here mess with them though. my suggestion would be to grab a babe bee and a balsa kit and enjoy flying.

Not my intention to be harsh, but just about everything with the "fly em" planes would lead one to frustration, even in top condition.

Ron

Cribbs74 wrote:You probably didn't damage the reeds, the fact that you can't access them is more than likely the culprit. Chances are that in the two years they lay dormant they became choked in castor goo.

I have little experience with pipe bombs, others here mess with them though. my suggestion would be to grab a babe bee and a balsa kit and enjoy flying.

Not my intention to be harsh, but just about everything with the "fly em" planes would lead one to frustration, even in top condition.

Ron

You're probably right. I was only able to get the Albatross to fly once, out of many attempts. The Camel never flew. I had the Albatross on 25 foot lines, and it went around so fast that I got really dizzy. When it ran out of fuel, it dropped out of the sky like a rock, and I dropped to the ground.

Well, hey you flew and got dizzy that's a good thing! To be honest I am surprised it flew fast enough to knock you down.

If you really want to have some fun, build something and your mind will be blown!

Welcome to the forum.

Ron

Remove your needle valve and push a small pin or wire through the spraybar. After that attach a syringe to the spraybar and blow a generous dose of fuel through it to remove any gunk. The reed assembly is a friction fit. Pulling and wiggling will allow the plastic assembly to come out. You could also immerse the entire engine in alcohol if taking things apart is not something you wanted to do. It also appears that the engine in the picture has some sort of silencer/muffler on it. I personally would remove it due to it robbing needed rpm's. Some of the Fly Em series had a very strange needle valve setup. It was more like a switch. It was a very poor design, very confusing and quite problematic. If you didn't hit it right on the mark, it wouldn't allow fuel to draw adequately.

As Ken said, the rear of the engine just snaps into place, so has to be maneuvered out some how but there is not much to grip onto. Your problem is guaranteed to be a gummed up spray bar or stuck reed. I'd support his suggestion about just soaking the engine and blowing things through. If for some reason you damage the plastic part then Cox International has a heap of new ones for sale which they've fitted Cox spray bars & needles to. They include a reed & retainer.
The Fly'em planes are best flown on pretty short lines so that they whip around better and maintain line tension. If they go too fast, just slow the engine down a little by richening up the mixture. Don't be like me whan I was kid. I thought I had to have every engine screaming its hardest every time. Don't know how I didn't cook more engines by running them so lean. That old Aeroflyte fuel I used back then must have had good oil.

Rod.

If flushing and a fuel soak doesn't work, the plastic back is pressed into the metal housing. Careful use of heat will soften any goo and they pop apart in a manner similar to old Tupperware - with difficulty.

Phil

Well, I tried a couple of things tonight. First, I zip tied the engine to a piece of wood, hooked up a syringe full of fuel to the inlet, and tried to start it. It would pop, and actually ran slowly for a couple of seconds, but that was it. I noticed while flipping the prop, that it was spitting fuel out of the hole in the back of the reed assembly. That didn't seen right to me.

Then I tried to get the reed assembly out of the crankcase. It didn't want to move, and I didn't want to break it, so I put the engine in the freezer for a while. After it got cold, I tried it again, and this time, it came apart. To my surprise, there was no reed in it. Now, I'm not sure if the reed flew out when the reed assy came out of the crankcase, or if it disintegrated at some point, and got blown out the exhaust. Both of these engines exhibit the same symptoms, so I'm going to take the other one apart and see if there's a reed in it. They were both running fine until I crashed them, and then neither one would run. Maybe the fuel I was using, dissolved the reed, I don't know.

So I guess the question now would be what do I use for a new reed. At this point I don't know what they look like, or what they're made from.

Here are a couple of pics.

Genius! Freezer time! (also gets batteries out of mag lights)

The reed retainer looks missing too. A floppy disk can be cut into an oblong reed very easily.

https://www.coxengineforum.com/t3064-how-to-make-reed-valves-out-of-a-floppy-disk

although there are other sources of heavy Mylar.

Phil

The reed retainer looks to still be there. The original reeds were star-shaped like the original Cox but were only ever mylar to my knowledge. I think the diameter is slightly different to Cox.

Bernie had?/ some of these don't know if he still does but you could ask through Cox Inter. and see https://www.coxengineforum.com/t9943-to-which-engine-does-this-part-belong?highlight=what+engine+does+this+fit didn't see them on there site ?! Eric

getback wrote:Bernie had?/ some of these don't know if he still does but you could ask through Cox Inter. and see https://www.coxengineforum.com/t9943-to-which-engine-does-this-part-belong?highlight=what+engine+does+this+fit   didn't see them on there site ?! Eric

Yep. Found them on Ebay. Got two coming.

Still waiting on those new venturis and reeds from Cox International. In the mean time, I decided to try to make a reed out of a floppy disk. I cut out a crude shape that would fit in the groove in the venturi, installed it, and put the engine back together. I then tried to start it, and it did run for a few seconds. Then it went back to just popping but not running. I took it apart again, and the reed was gone...again. I got to looking inside the crankcase, and I could see the reed jammed up in the cylinder, below the piston. I removed it, and there was still something in there. It was the original reed. I got that out too. Now the mystery is solved regarding where the original reed went. I don't know what made it come out of the groove, but I think it was the nosedive into the ground on the last crash. It does not appear to be usable anymore, but at least I know what they look like now,

That is not a groove as such. It is a space between the housing and the retainer. The housing has a clip-on retainer that you should be able to snap off. Rather than trying to flex the reed to Fit in the "groove" (the gap between the housing and the retainer), the retainer should be removed, the flat reed placed on its seat and the retainer snapped back into place. This will save the integrity of the reed rather than distorting it out of shape on installation.
Actually, I was going to suggest that you look inside the engine for the mysteriously missing reed, but I figured you would have thought of that.

Rod

I have never had occasion to remove the back plate on any of my Testors 8000 (pipe bombs), but I would think they would have something (equivalent to Cox) that limits the travel of the Mylar reed to prevent the reed from getting sucked into the crankcase as your two reeds did...or at least a stiffer Mylar.

George

gcb wrote:I have never had occasion to remove the back plate on any of my Testors 8000 (pipe bombs), but I would think they would have something (equivalent to Cox) that limits the travel of the Mylar reed to prevent the reed from getting sucked into the crankcase as your two reeds did...or at least a stiffer Mylar.

George

I think stiffer is the answer. The reed is only retained by the outer ring of the retainer. No wire clip & no plastic tabs. That's why it's probably necessary to use a star shape reed like original, so that it's supported by four points. The "oval" reeds like later Cox may fold & pop out too easily without additional support.

never had one apart and didn't know that it would separate to put the reed in , Thanks Rod

I like that design "cap-style" retainer better than the Cox flanged one. Still curious why the original reed got sucked into the engine. Did you perhaps force some fuel (or compressed air..) through the tank or venturi without disassembling the engine, in an effort to flush it out? Doing that could have caused the reed to flex enough to pop forward out of the retainer. I agree also that the 4-pointed "star-shaped" reed would offer more radial-support when flexing "inward" (under crankcase-vacuum) than an oval shaped reed would. The Cox design cap that uses an oval-shaped reed, looks to have a little more "retention-area" to it's flange.



See if you can measure the thickness of the old reed (if you still have it..) using a vernier-caliper or a micrometer. Cox Mylar reeds (either shape) are .005" thickness.. but as stated; the Cox reed may be smaller in diameter. The Testors reed may be slightly thicker if it "is" of a larger diameter. Knowing this might be valuable to the success of making your own reeds to experiment with in the future.

Our OP already has the solution by purchasing these ftom Bernie.  You can easily see here that the retainer is separate due to a slightly different colour.

Oldenginerod wrote:That is not a groove as such.  It is a space between the housing and the retainer.  The housing has a clip-on retainer that you should be able to snap off.  Rather than trying to flex the reed to Fit in the "groove" (the gap between the housing and the retainer), the retainer should be removed, the flat reed placed on its seat and the retainer snapped back into place.  This will save the integrity of the reed rather than distorting it out of shape on installation.
Actually, I was going to suggest that you look inside the engine for the mysteriously missing reed, but I figured you would have thought of that.

Rod

That's good information to know. Thanks. Just need to figure out how to get the retainer off without breaking it now. I can get it to rotate, but so far, it won't move axially.
I'm learning as I go here. Don't want to screw anything up permanently. Seems like these engines are getting closer to running again, and maybe flying again.

roddie wrote: Still curious why the original reed got sucked into the engine. Did you perhaps force some fuel (or compressed air..) through the tank or venturi without disassembling the engine, in an effort to flush it out? Doing that could have caused the reed to flex enough to pop forward out of the retainer.

The engine was running fine right up until the plane nosedived into the ground after a botched hand launch. It would not run after that, so I figure that's when the reed came out of the retainer.

roddie wrote:See if you can measure the thickness of the old reed (if you still have it..) using a vernier-caliper or a micrometer. Cox Mylar reeds (either shape) are .005" thickness.. but as stated; the Cox reed may be smaller in diameter. The Testors reed may be slightly thicker if it "is" of a larger diameter. Knowing this might be valuable to the success of making your own reeds to experiment with in the future.

The reed mics at .006 inch. Diameter, as close as I can measure it, is .490 inch. I might be able to make a punch at work which would knock those out nicely.

TLAnderson wrote:

roddie wrote:See if you can measure the thickness of the old reed (if you still have it..) using a vernier-caliper or a micrometer. Cox Mylar reeds (either shape) are .005" thickness.. but as stated; the Cox reed may be smaller in diameter. The Testors reed may be slightly thicker if it "is" of a larger diameter. Knowing this might be valuable to the success of making your own reeds to experiment with in the future.

The reed mics at .006 inch. Diameter, as close as I can measure it, is .490 inch. I might be able to make a punch at work which would knock those out nicely.

Yes.. the diameter of a Cox .049 reed is .450" in comparison. I'm guessing that's why Testors went with slightly thicker (by .001") Mylar.. for less "flex" over the larger surface-area.

Very cool if you have the capability to make a reed-punch tool. Just a S.W.A.G... but the radius between the legs of the star looks to be around .265" (17/64").. when gauging with that size drill. The distance in from the edge could be calculated by measuring across the center; between legs.. and subtracting that measurement from the diameter and dividing that figure by two. If it's a perfectly "symmetrical" design and has a .490" OD.. it would be .1225"..

Well I got both of the engines to run after replacing the venturi assemblies with the new ones from Cox International. The reed was gone in the engine in the Camel also. Found it inside the engine. Both of the engines exhibit the exact same issues. Probably because they both experienced the same damage.

They will both run until the battery clip is removed from the glow plug, then they quit.
The engine in the Albatross did get to where it would run for a bit without the battery clip on it, but then the starter spring broke.

They both seem to consume fuel at a very high rate. Maybe a minute run time on a full fuel tank.

I'm thinking that I've messed around with these things about as much as I'm going to.

TLAnderson wrote:I'm thinking that I've messed around with these things about as much as I'm going to.

Send 'em to me. I'll whip them into shape....

The Lion Tamer Mark