Cox 020 PeeWee rebuild questions -update

LooseSpinner99 Sat Dec 07, 2024 3:27 pm

Hi davidll1984,
Thanks very much for the detailed "cleaning for storage" advice. I will have to order some methyl hydrate just to have it on hand. Is this the same as the "methanol" that is used when mixing one's own fuel? Does it need to be reagent grade? I found a quart (about a liter) on Amazon for about $14 USD.

I liked the suggestion to run the engine occasionally to do what has been suggested. That is learn the "feel" of tuning the engine. But if I find that for some reason, I can't run it for a longer period, I will perform the preservation work.

Hi Balogh! That was awesome that you were able to record the speed! The propeller is the standard Cox 4.5x2 grey propeller. I have an app on my phone that records and shows real time frequency spectrum. But I did not think to use it. I'll have to try that to see if I can get the speed that way as well. It would be a useful engine tuning tool.

I know this has been a long thread. Early on, I said a friend had given the motor to me recently. It was from his childhood. His childhood friends swapped a lot of stuff back and forth. He told me that this little engine had been "well used" by the time he got it. So how "worn in" the engine is, I have no idea or if that would affect top speed.

I have run the motor two more times since taking the video. Just to see if it started repeatably and it did! I was just excited that it started repeatably. But next time I'll try the app on my phone to see if I can tune it to its peak speed. I will let you know what I get.

Thanks,
Dave

LooseSpinner99 Sat Dec 07, 2024 3:33 pm

PS
I am using SIG Champion fuel with 25% nitro.

Dave

LooseSpinner99 Yesterday at 6:14 pm

Hello to all and Happy New Year I hope!

It has been a while since I checked in. I've been running my first Pee Wee 020 rebuild several times now. I tried using a syringe to make a sort of larger tank for the engine to get longer runs. See the below photo. The syringe was about 10-12ml volume. But I found out that even that the weight of that small column height of liquid forced open the reed valve causing fuel to dribble out of the cylinder exhaust ports while trying to start it. The guy in the photo background is not me. He is Tim Fagan. The friend who gave me the motor.

Cox 020 PeeWee rebuild questions - Page 6 Image010

I reverted back to having the syringe laying on the table and every couple of minutes I would use it to top off the 020 tank proper. But I did not raise the syringe above the height of the tank! I was able to get a run of about 10 minutes with time to play with the NV.

Balogh, below is another short video of the long run with the best NV setting I could manage, and I was hoping you might read the speed again with your method to check my tachometer (which can be seen in the background of the video). My measurements were around 16,8K rpm. But I am frustrated because it does not run steady. The speed was varying from 16.3K to 17.3k. I'm not sure if that is normal or if not, what might be causing it.

balogh Today at 7:41 am

Hello Dave,

I audiotached your video and measured a tad higher than 17k rpm:

Cox 020 PeeWee rebuild questions - Page 6 Screen61

Whether this is normal speed depends on what fuel blend, and prop size you are using? Higher nitro and/or smaller propeller dia and/or propeller pitch will result in higher engine speed.

I trust it helps.

On the other hand, I believe the hydrostatic pressure of the fuel column in the syringe is not acting on the reed valve, but presses extra amount of fuel through the carb...so a slightly leaner setting of the needle valve will help avoid the overly rich mixture, causing fuel to dribble out of the cylinder exhaust ports while trying to start the engine..

Andras

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Cox 020 PeeWee rebuild questions