combatpigg

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That's impressive..!
Just being able to change the normal bark of a Cox engine to music is a novelty.

AndyW

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Click on the Youtube text at the bottom and that will take you to my Youtube Channel. It's been mentioned that for a pipe, the timing isn't the best but despite that, getting an extra 1.5 to 2K isn't bad. Not to mention the cool factor and that oh, so sweet, pipe sound. Throttling performance is mostly retained, some tweaking required. In the air, with the prop unloading, throttling is as good as ever.

Good find on this, I have the pipes made by CS (Chinese) engines from almost 10 years ago. Time flies, time to get to it and get at it before it runs out. Killing time isn't murder, it's suicide.

AndyW

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This was a company called, Flyquiet, as I recall. The "pipes" worked but for the weight and bulk, an extra 500 PM didn't have much appeal. I used their products mostly for exhaust extraction and as an after muffler.

AndyW

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Pond Skipper,

Can you post a video? I would LOVE to hear that puppy wail.

Pond Skipper

Thank you Chuck, its been something on the to do list for some years now.

The pipe design has a big factor in function regardless how dirty the engine side is set up.
The 3,260 rpm boost is a testament to the pipe design.
I will control the rpm with prop selection if it tries to exceed 25k

Yes plan on it Andy - will be setting up the engine on the Skorch and will post a full routine start up and flying vid.

The simple TD design seems to be ok with its timing to the pipe thus far I need another break in run and then lean it out to see how the engine temps hold up in the air.
- 2 large boost ports no bypass flutes

With the Kustom Kraftmanship crank case rear plate pressure tap I had the NV at 1.8 turns keeping it rich for break in.
When it got on the pipe fuel draw increased - I wont be getting 6min runs anymore my guess about 5mins at best.

Pond Skipper

Andy I liked your work with the Norvel .074 where did source the small header pipe did the bolt pattern match up or needed mods??

AndyW

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Thanks, and the header was made for me by Japanman just for the .074. He does amazing work, has a CNC lathe now. I haven't been in touch for a while, maybe he's been recruited by the Japanese bid to land their first man on the moon.

This reminds me of the CS .049 I got some ten years ago. It needed a lot of rework especially the head, mine is now rigged to take Nelson plugs. Despite that and despite using their pipe on this engine, just as designed AND using a tiny prop, it never did over 18K.

Noted was that the liner had a HUGE amount of exhaust lead as one might expect,,, yet the engine is a dud.

I hope to have another look at it this summer, and maybe a good start would be to get some timing numbers off of it. I understand that it was supposed to be a GZ clone that ran really well.

Still, we're getting some satisfying results by just sticking on a pipe. It's good to see that they're available now. I have four of the CS pipes and the curious thing is, is that none of them are identical. Hand made, looks like using the TLAR method.

I also have a lot of Norvel cylinders that I can chop up to perhaps maximize timing for the pipe. These came real cheap from Litemachines. Maybe just grind away, bit by bit at the top of the exhaust port? Maybe just a slot?

aspeed

My unpiped CS was no better than a TD. I made a Nelson head many years ago, and it didn't help at all from the stock button one. Lately I copied the Picco P0 head with the turbo plug, and it goes quite well, maybe 8,000 rpm better. The GZ I have was improved with the turbo head, from 17,000 to 21,000 on the 4 1/4 - 4" APC, but isn't up to the TD # of 22,900. The CS is 27,000 now. I haven't had time to play with the piped CS yet. (it has only been 20 years) Your Norvels with a pipe may just need a thicker gasket and maybe use no shims in the head. It may save cutting too far.

Pond Skipper

Bummmah I was hoping there was some small header pipe sourced lol but there is hope I have seen a few options I can dig back up.

My CS Speed engine has never been ran yet but has been checked out so far looks feels ok no leaks or pin holes in the case.
The sport engine has but needs more break in time so far so good. I haven't sourced additional glow plugs for this as of yet.
I am tempted to source a sonic cleaner that engine among a few others could benefit from a once over prior to heating up.

Yesterday I installed some new 2.5mm head bolts the flat head bolts limited a secure even feel.

AndyW

My Feedback: (1)

Thanks, that's a good tip,, I'll try that first. But boy, when you see the exhaust lead on the CS,,, it's pretty wild. Lots of room here to experiment and cut and try.

Pond Skipper

Here is the set up for a RC car engine on a tuned pipe OS .18 puts out some HP

Pond Skipper

Found this old Dale Kirn had this diagram for cylinder port mods for more rpm on the TD

combatpigg

My Feedback: (3)

To be that exacting, I think you could use a crankcase with an access hole cut in the bottom of it as a holding fixture that you could adapt to the snout of a die grinder.
Pretty delicate surgery.

aspeed

We turned off the fins of a worn out cylinder, and held it in a collet, then screwed on the cylinder that we wanted to cut on the milling machine. Tried a few different things, none really made a lot of difference. It was quite a while ago. I remember a guy that knew a lot about the TDs. Al Steggins. He could get them going good.

combatpigg

My Feedback: (3)

The "standard" Killer Bee ports are large enough to support ungodly rpm with a 4.2 x 4 prop, so yes that would be hard to improve upon measurably.
What I'd like to know is if the NIB Killer Bee I ran used the same cylinder as a TD or not. I didn't take the time to compare them before sending that engine back to Ptulmer.

Pond Skipper

Back in 96 when the first killer bee was made it was double exhaust slits per side, the lower slits had a bigger gap then the top ones for SPI function.
Only spent fuel / oil exits the top slits the top of the piston does not clear the lower slits. The original KB has two bypass ports and 1 boost flute per side.

Because the piston / cylinder set is tapered and matched with the inside cylinder polished to a mirror finish odds are great you had a all original KB.

When the Venom came out they used a single exhaust port per side tapper fit, deep cut transfer ports and 1 boost flute per side.
http://www.mh-aerotools.de/airfoils/cox_venom.htm only 1000 engines ever made.

combatpigg

My Feedback: (3)

That's an interesting write up, but I don't understand their self imposed 22,000 limit. For C/L Combat, 22,000 [with a 5 x 3] was hardly good enough to keep the lines tight on a windy day. I never failed any moving parts while running them at 23,000 to 24,000 and that was with standard weight pistons.
You really needed 24,000 for the planes to have decent pull and come out on top when the lines got tangled with the other guy's plane.

combatpigg

My Feedback: (3)

That's an interesting write up, but I don't understand their self imposed 22,000 limit. For C/L Combat, 22,000 [with a 5 x 3] was hardly good enough to keep the lines tight on a windy day. I never failed any moving parts while running them at 23,000 to 24,000 and that was with standard weight pistons.
You really needed 24,000 for the planes to have decent pull and come out on top when the lines got tangled with the other guy's plane.

Pond Skipper

Agreed 22k seems odd for the Venom I guess the idea is to use the additional torque rather than the push past the recommended top end - perhaps static top end.

Japanman

I was mentioned, so I thought I might humbly offer my experiences.
Firstly, listen to what Andy W says! Andy has tested a lot. You just can not value that enough.

Secondly, running a pipe is cool. Way cool. Only do it if you are into it, you will learn a lot, but you may face a bit of adversity. The main problems are:
heder pipe joint coming off / failing.
Heder flange coming loose.
If you are fabricating your own stuff, keep the above in mind, using cap screws for the heder flange, and high grade silicon tubing ( I think it is food grade) for the joints may give you a head start.

i found cox engines tended to wear out really fast on a pipe when pushed beyond a 5x3. I suspect it was due to the steel piston and cylinder getting too hot, and the oil vaporising.
Your results may vary, but I found running a mini mousse can muffler on a cox and a 5x3 on 15% fuel to be just about perfect. It might be possible to match or even better the rpms with open exhaust and a quick slosh of nitro, but it sounds so much sweeter on the pipe, is much quieter and seems to be keeping the engine healthy by keeping grit out. It's also nice to be able to direct the oil away in a neat manner.

A few words on the cs engine: I am by no means an expert here, but I own two and a half GZ engines, and love them for the rough beasts they are!
If you have a newish one, have you checked the conrod to crank pin fit? All the engines I saw had a radius on at the intersection of the crankshaft web to crank pin, but the con rod bushing needs to be countersunk a little to allow the rod to sit up hard against the web, otherwise it may rub the crank case, and may even be forcing the piston to rock.

i hope this is of some help.

Stefan

Pond Skipper

Hi Stefan, what was your spec's do you have photo's of your set up, degrees of timing, did you modify the bypass ports?

Here is my current set up:
4.2 x 4 do to the 170 deg duration to keep a reasonable length of pipe down the fuselage and rpm in check.

170 x 1700 / 25000 rpm for 11.5in subtract the reduced area of the cox muffler acting like a anti reversion zone
- my guess I am actually needing around 10.5in - set up is now at 10.5in actual now ready to test
- will post static results simulated unloaded flight with 4.2 x 2 - 25k rpmfor (4.2 x 4 unloaded 85-95 mph)

I have 3 zip ties on the engine side, rear crank case pressure, 1 exhaust port is blocked the header feeds straight to the rear exhaust port
There is some transition aluminum tube inside the silicone tube. 5 channel Skorch -12.4 oz ready to fly less fuel.

Japanman

That's a cool setup, you sound like you know a lot about it.
I really cut loose over 15 years ago on a cox TD049 I made an outboard for, and a friend made the mini tunnel hull boat.
At the time replacement sure start cyclinders were cheap, so I went through them like candy!.
My final setup had a split heder I forged from thin copper, that matched to twin exhaust ports on the cylinder. The fastest running cylinder had raised exhaust ports, and it was quite something when it came up on the pipe, but from what I hear about pin breakages in TDs I doubt it was doing much over 25k. In the end the boat would blow over at speed, so I canned the project.

at a guess I would say it had about what you are running: 170 degrees but it could have been less.
I didn't modify the bypass cylinders, though I did try a single exhaust for a while.

Pond Skipper

Here is what I did with cox muffler added a 3/4 dia shim inside the groove of the muffler body to block off one exhaust port.
Also took two shims to get to 170 deg. I have thought about the same thing just using the stock cylinder / pistons cheap throw away.
The challenge I am having is the long header pipe set up its eating up way to much real estate. Do you have any pics of your pipe setup on the boat?

Pond Skipper

The dual header idea you implemented sounds great. I am curious how the raised timing effects open exhaust rpm or perhaps with a simple dual pipe muffler with the added bonus of the sound it would make.

Japanman

Thinking about it now, I remember testing the hot cylinder with an apc 4.7x3 prop, and it ran about the same (or better even) than my one TD cylinder on the TD, with the exception that it used about 3times the fuel!
On the pipe, I don't remember it using huge amounts of juice, but I very rarely if ever ran out of fuel... Something would break, the boat would flip, or the engine stop well before then. But maaaaan it was cool when it went!
I found the outboard the other day. I had a look for the pipe, but I could not find it.
I think it is somewhere though.