Re: Cox 020 PeeWee rebuild questions

balogh Mon Nov 11, 2024 1:36 pm

Dave, before applying the CA you may want to do an underwater leakage test in a glass bowl filled with water and the tank and backplate submerged with the crankcase and cylinder possibly staying above water. If you crank the piston halfway up the cylinder, then the crankcase is closed by the piston. Pressurizing the tank with air pushed into it with the syringe may help you detect where the air leaks i.e. between the insert and backplate, or along the NV threads? A hairdryer will help you dry the engine afterwards.

A leakage between the insert and the backplate is not critical..remember the fuel filling nipple is right next to it through which the tank interior communicates with the outside, anyway...the NV thread.leak needs to be doctored though..

LooseSpinner99 Wed Nov 13, 2024 2:59 pm

Hi All,

I performed the underwater leak check proposed by balogh. I could not find a clear (enough) bowl or container to perform it in so I used a shallow plastic bowl with about a 2 inch inspection mirror in the bottom. See attached photos. It worked great, except I got leaks I'll cover after the pictures.

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I filled the bowl up to just below the cylinder with the engine sitting on the backplate. When I lift up the motor and tilt it slightly, I can see the backplate perfectly in the mirror.

Now the bad news. I saw that I was still getting slow leakage out the air/screen inlet. Very slow: a bubble would form, long pause, then another bubble, and so on. After several tries I could still not specifically locate where the leakage around the NV was coming from insert/backplate or insert/NV threads. I think I'm going to try to use some CA glue at the insert to backplate and re-leak check. Balogh, I'm not sure I understand how you mean to use silicone fuel tubing to help seal the NV threads if that is the problem. Can you please post a picture? Thanks!

The good news is, this is the second time I've used the Teflon tape to seal the backplate screw heads and they did not leak. I'll post pictures of what the disassembly condition is of the Teflon when I disassemble the engine. That means I didn't just get lucky the first time it worked. When I do it a third time and get no leakage, I'll be pretty confident in the method. Also, no leakage was noted at the fuel tank/backplate joint or the fuel tank/crankcase joint.

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Putting the Teflon tape, rolled into a ball, down into the two top crankcase screw holes seemed to work very well. I started with lengths of Teflon tape about 15-20mm. The balls were too big. Finally, once I got down to trying tape lengths of 5-7mm, the rolled-up balls fit just slightly snug into the screw holes. I'll show pics of what the breakout holes in the crankcase look like as well once I disassemble the engine.

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To address the leakage observed from the air inlet, that has to be coming from the venturi rubber "washer" seal I plan to try and fill the pore in the backplate mating surface for this seal. I'm also going to install a new seal. This seal has been through several assembly/disassembles and maybe not its best now. Also below is an older picture (last week) of the seal in position on the fuel tank. You can see that it does not fit completely into the seal groove area. It appears "loose" at both the inner diameter and outer diameter of the seal. I suspect that pressurizing the fuel tank may "push" the seal out of center and potentially uncover the casting pore in the backplate. I have a 10 pk of new seals coming. So, I'll work on the backplate pore first. Once I get the new seals,
I'll reassemble and try again. I will re-run the Sharpie mark matting contact witness mark test again, making sure it looks good before re-assembly.

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I hope I'm not boring anybody to death with all this detail!
Thanks,
Dave

balogh Wed Nov 13, 2024 4:26 pm

Dave, did you turn the needle valve into fully closed position before you pressurized the tank? Air from the pressurized tank may leak through the fuel line into the venturi if the NV is not closed, so the bubbles appearing in the air intake may not be necessarily escaping from the tank around the O ring..

Below is a photo of how I would seal the NV threads with a silicone tube:

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You can remove the NV spring for good, but cut the tube end perpendicular to its axis so that it sits with its end flat on the face of the backplate top and seal well. Select a tube whose internal dia is not more than the outer dia of the NV so that the tube seals the threads too.
Cut the tube to the length where it will be snug when the NV is open to about 5 turns, so that when the engine runs at its peak at about 3-4 turns the tube will be slightly compressed and not only seal but act as a spring, too, preventing NV self-rotation due to vibrations.

LooseSpinner99 Wed Nov 13, 2024 4:36 pm

Balogh, I haven’t disassembled the engine yet. I thought I closed the NV. I just checked and it feels closed. The original NV was slightly bent so this is a new NV. It doesn’t mean the NV isn’t leaking even if it’s closed and new!
Dave

balogh Wed Nov 13, 2024 4:39 pm

When you disassemble the engine, pull a fuel line on the fuel nipple and pressurize it with a syringe with the NV closed, under water, and check if the valve is closing well or not. Bubbles should not appear at the air intake if the NV closes well.

706jim Wed Nov 13, 2024 9:32 pm

I flew quite a bit of free flight 50+ years ago using the Pee Wee 0.020 for power. I just loved that little engine. I've never cared for the spring starter so would hand flip the engine to get it going. Well any reedy has it's own decision as to which way it's going to run. When mine started backwards (often) I would just rest the palm of my hand against the rotating prop to stop the engine and then take another crack at it. Never had even a hint of injury from this modestly powered engine. No need for a rag or futzing with the needle valve. Anybody else here try this?

rdw777 Thu Nov 14, 2024 10:56 am

706jim wrote: No need for a rag or futzing with the needle valve. Anybody else here try this?

I’ve done this a lot Jim….Two .020’s I have with throttles, I just throttle them down and pinch the TeeDee spinner nut that is on them…. Ol’ Benny on my glider doesn’t have a throttle or the spinner so I just palm it as you say if it happens to start backwards, And before it comes up to full song….

049kid Thu Nov 14, 2024 12:30 pm

Hi guys,I have probably done the spinner pinch hundreds of times .I think most here do.sometimes if your quick you can flip it again and it will start with out glow clip attached .never questioned if their is added wear on ball and socket ?.sam

LooseSpinner99 Thu Nov 14, 2024 3:13 pm

Hi Balogh,
I just disassembled the engine this morning. See pics below. I do have to be careful about how much Teflon I put on. as a piece of Teflon was poking through the backplate on fuel tank side. The witness marks on the Teflon show that the screws bottom near the outside diameter at the bottom of the screw head.
Teflon itself is a lubricant so if a small piece were to break off into the fuel tank, I think the only risk is plugging the fuel pick up. Unless you can elaborate if you see other risks.

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Also, the little balls of Teflon in the upper crankcase holes look like they did not go anywhere, and I cannot see light through the breakout holes looking from the screw thread side, like I could before. I think that is a good solution.

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I did the leak check in water with the syringe on the fuel pickup barb with the NV closed. No leakage at all past the needle/sealing surface. Lots of bubbles out of the NV threads. So I found that the fuel tubing I have just barely fits onto the NV threads. Even so, when bottoming the NV, the tubing creeps up over the "flange" like feature just above the threads. So when I close the NV all the way and then back off 4-5 turns, the tubing is no longer contacting the backplate to form a seal. So, I have some thin wire, 30ga and 24 ga. I tried twisting the wire onto the NV to prevent the tubing from creeping up. I screwed the NV in and out a couple of times and I still get a little tubing creep. But I did the water leak check with the NV at 4 turns open and NO LEAKAGE! Yeah!
See below pic.

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I think arrival of my order of extra venturi washers is still a day or two away. So, I'm stopped for now. Once I get the new washers, I'll reassemble the motor and try again. I hope this could be the last issue.

Dave

LooseSpinner99 Thu Nov 14, 2024 3:15 pm

Update, the wrong picture got posted when trying to show the Teflon in the fuel tank side of the backplate screws. Here it is:
Dave

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LooseSpinner99 Thu Nov 14, 2024 3:19 pm

Another update,
Looks like I used the vinyl tubing for the fuel fittings. You said use silicone. I'll have to try and find some that is the same size as the vinyl tubing for the 020!
Dave

balogh Thu Nov 14, 2024 4:01 pm

Dave the silicon tube is for sealing the NV threads..it is rather flexible, vynil would not seal well on the threads in my opinion. Inside the tank you can use the vynil..sorry if I confused you. Also, add a washer to the NV that will stop at the shoulder of the NV and then add the silicon tube. The washer will prevent the tube from creeping up the NV.

LooseSpinner99 Thu Nov 14, 2024 4:38 pm

Thanks, Balogh!

I realized my error once I wrote the last post. I now have the right size 1/16-inch ID silicone fuel tubing ordered. Adding the washer to the NV is a great idea.

So, I'm on hold right now until I get my venturi washers and silicone fuel tubing.

Cheers,
Dave

TD ABUSER Sat Nov 16, 2024 2:10 pm

LooseSpinner99 wrote:Response to all, Ok! Next heat. Yes, I have a heat gun, so definitely my bad. Per rsv1cox, the damage has been done. I'll still wait and see once I get the motor apart. I still hope for no damage. It may be a couple of days before I get a chance to do this.

Separate question for rdw777: Please can you tell me why you use 2 head gaskets on your 020s? I've heard of using 2 head gaskets for 049 engines in the Texaco event. I suspect it is a way to slightly reduce power and increase duration, but that is a guess.

Thanks all,
Dave

I wanna BUTT IN...!

Glow plugs are very expensive so it's never a bad idea to experiment with more shims to see how low you can go with compression in order to make your glow plugs last longer.
Adding shims might also retard ignition timing just enough to get max benefit from a large prop [like a 6 x 3 on a .049].

TD ABUSER Sat Nov 16, 2024 2:17 pm

rdw777 wrote:
706jim wrote: No need for a rag or futzing with the needle valve. Anybody else here try this?

I’ve done this a lot Jim….Two .020’s I have with throttles, I just throttle them down and pinch the TeeDee spinner nut that is on them…. Ol’ Benny on my glider doesn’t have a throttle or the spinner so I just palm it as you say if it happens to start backwards, And before it comes up to full song….

All these years I've been tossing all my reedies that start backwards in the garbage... until I find one that runs correctly.
NOW you tell me that I should have given those engines that I've thrown away a second chance...? tongue

roddie Sun Nov 17, 2024 9:11 am

balogh wrote: Also, add a washer to the NV that will stop at the shoulder of the NV and then add the silicon tube. The washer will prevent the tube from creeping up the NV.

Here's some examples of what Andras is explaining. It can help to "smooth-out" an engine that runs erratically due to air-leakage around the needle-valve.. which is not uncommon.

Small (#2, 3, 4 etc.) steel flat-washers you'll find to be very useful to have on-hand for this hobby.

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Below photo shows a piece of steel rod that I use as a "mandrel" for cutting the silicone tubing. An appropriate-size drill-bit's "shank" will also work. A razor-blade is held perpendicular while rolled one revolution over the tubing, which makes it easier to achieve a cut-off closer to 90 degrees.

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Just an "FYI".. you can make small flat-washers from "thin plastic sheet" by first drilling the appropriate-size hole for the inside-diameter.. and then using a paper-punch to cut it out. Your washers will all have a 1/4" outside diameter.. but this often won't matter. You'd be surprised by how strong a little plastic flat-washer can be. Clear plastic "packaging" is ideal for this application.

Tip: Use the paper-punch inside a plastic sandwich-bag to avoid loosing the piece(s) you're punching-out.

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LooseSpinner99 Sun Nov 17, 2024 5:17 pm

Hi roddie,
This is great info! I never thought of using the packaging plastic to make washers! I’m finding #2 & #3 washers are very scarce!

I am familiar with the technique of using thin wall brass tubing sharpened on the inside or out and used as small punches. I’ve used this to make lightening holes in stick and tissue models that I’ve built!

Thanks again for the help! Still waiting for parts ordered.
Dave

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Cox 020 PeeWee rebuild questions