Cox 020 PeeWee rebuild questions

Hi Dave, You have break through from the tank screws here?

If so that is not normal….. I’ve seen some backplates on Bees that have had the tank screws tightened so much that they are somewhat caved in which allows the screws to go deeper into the crankcase…Is your backplate reasonably flat on the backside?

That may be as clean as the backplate will get on the inside… If there’s any crusty stuff left pick at it with a toothpick until you get all the loose stuff off then rinse again… The crusty won’t hurt its running as long as it is stabilized…

A good head will glow with two D cells…. Make sure your batteries are fresh and all wiring connections clean….The head clip needs to be clean too…Use a wire brush or fine sandpaper as necessary…. Here’s a photo of one of mine working on two older cells in my four cell box….Idle voltage on the cells was 1.45…. 1.25 under load… Compare with a volt meter if you have one…

The upper rear holes often break through to the case interior in the area of the cylinder threads.

Attached is close up photos.  Correct, the breakthrough is in the crankcase threads for the piston cylinder.  I was reading in one of the other posts that someone uses cotton fibers under the backplate screw heads and cotton thread in the tank to backplate "seal" grove of an 049 to prevent leakage in/out of the crankcase.  But I was wondering, there is a Loctite, No. 518 I believe that is non-hardening and forms a pliable gasket.  Perhaps a little dab will do me under the backplate screw heads to prevent leakage.  I'm talking about a very thin line of Loctite around the bottoming surfaces of the backplate screw heads just as I am installing them.  Does that sound like a possible plan?

To rdw777, I'll keep scrubbing the backplate more, thanks!  And I need to troubleshoot my glow plug power supply!

Wow, on the bench, normal view, the crankcase looks decent.  But at this high magnification there are a lot of surface imperfections!

Thanks for the clarification on the screw break thru…. Just wasn’t sure where you talking about…..
If you want to go the extra measure on sealing the tank, And I certainly recommend it, I’d stick to the proven method of the thread and cotton fibers…. One of the old gaurd here  recommended it a long time ago…. I do it to all my tanked Bees and PeeWee’s and I believe it helps tremendously….. I would be concerned with a gasket sealant that it might  sluff a piece off and go to where it shouldn’t be….A couple of PeeWee’s with this treatment….Soak the thread and cotton with castor oil to help things stay in place while assembling….

I solved the glow plug problem.  The new plug clip was not assembled correctly (maybe?).  I managed to disassemble the clip without damaging it.  I found that the wires had been crimped to the copper plate clips, but not stripped of the insulation.  I notified Cox Engines International to let them know.  Bernie took one or two apart and found that that was the way they were made but the crimps broke through the wire insulation more than mine.  Before disassembly, I did a resistance check of each wire/copper clip.  It all showed low resistance!  And that fooled me at first.  I soldered on new wires to try it.  Unfortunately, I broke the upper clip trying to shoehorn it back into the yellow plastic housing.  I used to big of a wire gauge, but that was all I had on hand.  So, I did a work around with an alligator clip (see photos.)  Bernie is sending me another new plug clip.  He stripped the wire ends and check a glow plug with it.  And it worked fine.  I must have just gotten a "one-off".

Ok back to cleaning parts.  I will stick with the cotton thread and fiber type seals as it is proven.

Cheers,
Dave

glow plug Clip

Let me Preface:
Bernie at Cox Intl
Matt at EX Models
both my FAVORITE vendors. and my vendors of choice

With that said....
MECOA sells a Holland Hornet Glow Plug Clip that I find much much better
https://www.mecoa.biz/shopdisplayproducts.asp?catalogid=1488



glow plug Ignitor
as mentioned in another thread:
https://www.coxengineforum.com/t17650-rcats-glow-driver?highlight=glow+plug+ignitor

the RCATS Glow Ignitor is the best. set this up with some molex and a Holland Hornet Clip, you are SET! |
it aint cheap, but it takes glow plug issues completely out of the starting equation
https://www.rcatsystems.com/store/lithium-glow-driver.html

Low resistance is the key for heating a glow plug well.

I picked up an RCATS driver at a swap in January for 10USD. It had a Dubro Kwik Klip on it, which was faulty. It would barely light plugs and sometimes not at all indicating 2 amps. I added an Anderson connector, and use my typical plug clip of similar style (wired with 16AWG) and it works very well indeed. I know Molex is a general term, but use a low resistance connector.

gkamysz wrote:Low resistance is the key for heating a glow plug well.

I picked up an RCATS driver at a swap in January for 10USD. It had a Dubro Kwik Klip on it, which was faulty. It would barely light plugs and sometimes not at all indicating 2 amps. I added an Anderson connector, and use my typical plug clip of similar style (wired with 16AWG) and it works very well indeed. I know Molex is a general term, but use a low resistance connector.

Here's the RCATS vid which also explains what Greg points-out in his comment above.

Wow this is some awesome stuff! Thanks. I checked out the RCATS website. Yikes! Yes, expensive and I only have one motor. However, if this rebuild goes well, I could end up with a couple more! I'll keep my eye out for one. $10 for one a swap meet is an incredible deal! I've not heard of the Holland Hornet engine, so I looked at info online about that. Very interesting an early competitor to Cox engines. EX Model Engines still has the glow clip in stock!

Engine part cleaning is about half done. The cylinder and piston cleaned up nice. Next is the fuel tank, reed valve area and crankshaft. I have to go get some 2000 grit wet/dry paper first. The needle valve is bent (outside the threaded area). So, it could work, but I'm waiting for new parts and the piston reset tool. It's on the way with the extra glow plug clip.

When I start putting the motor back together, should I use the "after run oil" or castor oil? I plan to use the after run oil after the test runs on the motor. But the motor may sit for a while as I build the model it is for.

Thanks again in advance for the help and this is a GREAT forum!
Dave

I suggest you use the after run oil, because castor, even if not as burnt fuel residue,  will turn into dense  goo after some engine shelf time,  that will make the engine tied up in the same stuck state you have received it in.

Some CEF members use hydraulic fluid as after run oil, and say it conserves the engine for a long time without "freezing" it..

I have some pneumatic tool oil I have used previously before joining the Forum. I read somewhere that it is ok and can be had at the local hardware store.

The $10 RCATS driver was a fluke. I figured batteries were dead and I could handle that. It's a nice, luxury even, piece. Until this year, I just used a C size NiCd. 15+ year old Sanyo 3000CR I had on the shelf. They still work fine, but self-discharge is quite high at this point. If I didn't have chargers etc., a couple D cells is great.

Soldering the leads on the Cox clip is a good move. There just isn't much room for larger wires, I think my Cox clip cracked.

Hydraulic oils are fine. Sewing machine oil is good too. I once tried to look up specs for air tool, and it seems like it can be anything. It's probably fine too.

If you end up having to mix fuel, my vote goes to Maxima Castor 927 for a few extra bucks. It won't setup for years and it runs clean.

Hi again Dave, Yes; this is a GREAT forum! It's GREAT to read your posts! You're obviously someone who will have good success with Cox engines. You've already read and applied.. or at least understood; the recommendations from others here. It's also GREAT for all of us... to read-through the thread.. and maybe learn something new.

These engines were designed decades before there were rechargeable batteries.. so you don't need any fancy expensive support equipment to enjoy them.

Most any petroleum-based lubricating-oil is going to protect your engine and its internals while in storage. The beauty of the "castor-oil" in your fuel-blend is; if you put your engines away indefinitely after running them... without any further attention, the components have that castor-coating which is like a "shellac-protectant". You'll need to apply HEAT to free them back-up.. along with a complete disassembly/cleaning to restore service.. but they'll generally be free from rust. Most of the seized-up model engines that you'll find.. need only the application of heat to get them back moving.

To all, thank you for your comments and advice on reassembly.  I will make sure the engine passes the blow and suck test and any leak testing once I get it back together.  But it could be very hard to hold off trying to start it until I get the model built for it!  I guess that will provide motivation to build the model well, but as quick as I can!

Next, I'd like to discuss the tank/reed valve.  I've read the thread regarding the "best reed for Cox engines".  The experimentation that has been done revolved round the 049 engines is the impression I got.  There was a short thread about Cox Pee Wee reed valves, and I read that too.  It sounds like the mylar reeds work fine with the Pee Wee.  I understand it is important upon reassembly to ensure the retainer clip goes in the right way and why and to ensure the reed valve can rotate freely beneath the retainer clip once installed.

I still have a couple of questions.  Attached are the photos of the cleaned-up tank, reed and clip.  The clip as some corrosion on it.  The reed looks pretty bad to me having not looked at an old use one.

The mating surface on the tank where the reed valve seals against looks kind of in rough shape.  Has anyone had any success lapping this surface to clean it up?  If so, can you please share your method.  I'm not sure if that mating surface is integral with the tank or a harder metal insert.  Or should I not touch that surface at all except to clean it with acetone?

The original reed valve - I read that Hopps No. 9 could help clean this up.  But you still have a bit of worn surface.  Please comment on how bad the wear is and if it is worth trying to clean it up.  Also, any comment on flipping the reed valve over to the "unworn" side for a fresh start, assuming I can get the reed cleaned up.

The final question for now is can the old retainer clip be used with the newer mylar reed or should I use the new clip that comes with it because of the difference in thicknesses between the copper and mylar reeds?  I read there is a difference in wire diameter between the old and new clips.  The new retainer clip may be designed to compensate for the thicker mylar material.  I just don't know.

Thanks, and I'm having fun and learning good stuff!

Dave

I would try to clean the beryllium reed before replacing it with a mylar..looks like having some goo and corrosion on it..to me a beryllium reed is worn when its tabs start to detach where they touch the harder clip..maybe applying some toothpaste then "sanding"on a glass sheet (I use clean 09 engine wrench for flat base when polishing glow head sealing surface)

I have never lapped a reed seat in an aluminum tank but would use the finest sanding paper, put under the bottom of a flat coin or small button battery, and rotate the seat around its axis against this sanding "disc" so as not to make any radial micro-scratches on it..I am doing the same rotational lapping on aftermarket COX 010 glow head seats if they do not seal well. A circular sanding mark will not tend to leak as easily as a radial one.

Yes! Perfect advice on lapping in a circular motion so the lap "scratches" are circumferential as opposed to to radial that could cause a leak path!
This is the method I used to clean up the back of the crankcase (on glass, w/400 & 600 paper.  I rotated the crankase by hand as best I could about the geometric center of the crankshaft.  It definitely wasn't perfect motion, but I'm not young anymore!  The crankcase surface cleaned up really well!

Two topics:
1 Fuel tank/reed valve contact surface clean up.
2. More reed valve cleanup plan.

For the fuel tank - I had to MacGyver a lapping tool. See attached photos.  I found that the aluminum X-acto knife handle fits inside the bigger diameter with clearance.  I thought I could wrap tape around the handle to take up clearance, but so the handle rotated easy with little to no sideways movement.  But before I did that, I had to true the bottom of the X-acto handle first.  It turns out the handle is 5/16" dia.  So, I drilled a 5/16" hole in a piece of wood with my drill press.  It's not a precision drill press, so I only got close to true straight up and down.  I used the piece of wood to guide the handle over 400, 600, and 1000 grit.  Then I double back taped a piece of 1000 grit and trimmed it flush to the handle.  With a little oil on the paper, I would twist back and forth on the surface with light finger pressure.  I'd do the back and forth about 10 times, clean the surface and inspect.  I did that three times and I think it came out pretty good without removing hardly any material.

For the reed valve - Your idea of using tooth paste, gave me another option. And, please let me know what you think of this. I was thinking of using some Turtle Wax polishing compound - Light to Med.  It says it is intended to remove light oxidation of your car paint, leaving an as new look.  The big benefit is had already having some in the cabinet!  I have two disk shaped ferro-magnets.  I was thinking of putting the polishing compound on the sides that attract, With the reed valve laying on one magnet face I would put the other face together.  Once together, I could twist the magnets back and forth.  I'm sure if a sides cleans up, it will only be one side as luck can go.  But I'm working on what to do then.  I measured the thickness of the reed I got .0020 and .0015.  I am also thinking if I end up removing 2 to 3 ten-thousands, even that is not a small percentage of the thickness.  What does a new reed thickness measurement range, if anyone knows?

Thanks,
Dave

Turtle Wax may be a good alternatíve to toothpaste. Just make sure the reed central seat lip is not excessively consumed by the polishing and remains flush with the seat periphery, because the reed should seal without its center buckling.

The venturi "mouth" looks good Dave. It's fun making your own tools for working on these little engines. If the reed doesn't clean-up enough to use; you can always get a kit from @ExModelEngines (Matt) or @Cox International (Bernie). They both stock the kits which include a new Mylar reed and a new circlip for it.. as well as 4 new screws for the tank assy., a new fuel-line and spring, a new crankcase gasket, a new glowhead gasket and a new venturi gasket.



I like your idea of using a pair of magnets to sandwich/polish the delicate copper/beryllium reed..

Hi All,

Thanks for the comments. I hope to give the reed polishing a try today. I will of course let you all know how it goes.

Dave

Another product that may be useful is Brasso. By cleaning off the oxidation will allow one to clearly see surface imperfections and better deal with them.

Thanks GalllopingGhostler,

I think I will try the Brasso first, but I have to go get some. It might be a better idea to start with, then get more aggressive with the car polish if I have to.

Thanks,
Dave

An option may be common kitchen copper cleaner for copper bottom pots and pans. It's got some chemistry that counteracts copper corrosion, just go light with the mild abrasive included.

Practice on a dirty penny or old old brass doorknob first, to get a feel for the product first.

Much of what we here on CEF have learned is not cookbook but thinking outside the box. Also, some are better at some methods than others.

Hi All,
Had a bunch of other life thing to take care of until now.  That's the reason for the break.  
Comment to Roddie, yes, it is great fun and a challenge to my creativity (assuming I have some) coming up with the tools to work on these little engines!
I got to the hardware store and found the Brasso.  To my surprise Tarn-X was right next to it on the shelf so I bought both to try.  Both labels say they clean copper.  I could not find a cleaner that was specific just for copper.  In the last few days, I tried the Brasso with a Q-Tip on a flat surface.  See attached photos and please let me know if you think it is ok to give it a try in the rebuild.  The "before" pics have already been posted if you're seeing this for the first time.




Thanks again!
Dave