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Post  layback209 Wed Sep 22, 2021 8:34 pm

Taking a break from my garage reno to rehabilitate some cox engines I came by over the years.

They all look reasonable and some a rougher than others around the edges. Time to clean, and take inventory on what parts I need to order from Bernie. Compression varies from average to significant. I didn't play around to much as I want to clean them good first.

If I number from top to bottom with the top starting at one. I think number 3 may be a suprise.

What you think lol, might be fun. After they are all restored do a test using the same prop and glow head to see which one holds the best note and turns the most rpms?

Who knows maybe they will all be the same.Which teedee will perform the best?  20210914
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Post  balogh Thu Sep 23, 2021 1:04 am

If they are all well broken in, their crankcase seals the shaft, the NV does not allow air ingress, and their compression is not much different, I would not expect wide performance gaps. Based on its carb body though, the one on the bottom looks more like a Medallion, that will never reach the performance of a TeeDee, even if it is run without muffler like all others.
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Post  davidll1984 Thu Sep 23, 2021 11:41 am

I say no 4 with the blue spiner I don't know why him but I like blue Small Cox Logo Babe Bee .049 Popcorn
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Post  layback209 Fri Oct 01, 2021 8:01 pm

Update, exterior cleaned, tare down has started. Looks like these motors have a bit of plier mark character. See if I can clean some of that up. I placed an order today with cox international to get the tune up parts needed to make these runners again.

Hi David, I think you picked a solid contender. It's interesting. It had a pressure hole drilled in the backplate, however it was later filled with epoxy. The top end is pretty nice.

Hi balogh, good points. Cool if one is problematic it will under-perform from the rest. might be a good way to troubleshoot. Maybe I'll do a bell curve plot or something if they are close to see what the mean operating rpm.
Which teedee will perform the best?  20211010

Progress pic
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Post  layback209 Sat Oct 02, 2021 12:05 am

Did a little more work tonight. Interesting no. 2 crank was previously polished. Pretty cool.  Polished the other cranks tonight.  Process was scotch bright like pad, coarse to fine version then final polish with paper towel loaded with some cheepy dremel kit polish compound. Came out pretty good.  Chucked it in the drill press via a stud + prop nut I had.Which teedee will perform the best?  20211011
Which teedee will perform the best?  20211012
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Post  layback209 Mon Oct 04, 2021 2:59 pm

Little more progress. 2 engines cleaned, oiled and ready for assembly. Wow did my ultrasonic do a reasonable job. The jar of fuel mix placed in the water bath is no longer transparent and full of crud.

Here's an interesting side by side of a teedee crank vs a medallion one. I'm guessing the medallion one was cheaper to make this way.

Which teedee will perform the best?  20211014
Which teedee will perform the best?  20211015
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Post  balogh Mon Oct 04, 2021 3:24 pm

Medallions were called the poor man's Tee Dee😃...no offense meant..

https://www.mh-aerotools.de/airfoils/cox_frameset.htm
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Post  layback209 Thu Oct 07, 2021 11:05 am

Woohoo Cox parts order has arrived! Can get back to tunning up these screamers.

Thanks for the link balogh there's some awesome information on there. This medallion appears to be in really good shape.

Which teedee will perform the best?  20211016

Looking forward to getting back to these motors, I just about wrapped up my garage reno which was absorbing lots of my evenings.

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Which teedee will perform the best?  20211017
Which teedee will perform the best?  20210915
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Which teedee will perform the best?  20210917
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Post  layback209 Thu Oct 07, 2021 11:09 am

I learnt that electrical is fun, insulation is a job I never want to do again, and drywall ain't to bad.

I ran a 100amp sub panel to the garage, have 2x 220v outlest for welding, and have 20amp circuits on the machine side. Never more than 6 ft from an outlet now. It's much better.
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Post  getback Fri Oct 08, 2021 8:01 am

Looks Good man you have done something we all need and despise LOL Parts in cheers cheers
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Post  layback209 Mon Oct 18, 2021 11:01 am

@getback wrote:Looks Good man you have done something we all need and despise LOL Parts in cheers cheers

Thanks get back lol.  It has made cleaning engines so much more appealing to hang out in a nice space.

Update; motors are all ready to test. Hoping to have some numbers soon to share.  I forgot how much compression you get ftom a TD head.  Man 2 of them were very dirty, had to change out my cleaning fuel twice to get it done.

With this many motors think I need to come up with a new test bench so I can change engines more efficiently. A nice problem to have.

Plan to use a apc 5x3, 1 head gasket, standard TD high comp glow head and sig 1/2a 25% nitro go juice.

Ready for assembly
Which teedee will perform the best?  20211019
Ready to test. They all will need a little run in after the reset. Medallion here for comparison.  
Which teedee will perform the best?  20211018
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Post  Cribbs74 Mon Oct 18, 2021 12:17 pm

General rule is 1 gasket for every 10 percent of nitro. So with 25% fuel you would require 2-3 gaskets. It will still run with one, but too much compression is almost as bad as too little. Just a thought and something to experiment with.

Ron
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Post  layback209 Mon Oct 18, 2021 12:36 pm

@Cribbs74 wrote:General rule is 1 gasket for every 10 percent of nitro. So with 25% fuel you would require 2-3 gaskets. It will still run with one, but too much compression is almost as bad as too little. Just a thought and something to experiment with.

Ron

Thanks Ron appreciate the guidance. I'll definitely try that. So far I have just made sure everything is sealing properly. I have no idea where to start so that helps.
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Post  getback Wed Oct 20, 2021 8:11 am

There looking good layback209 , should bee fun running all those engines one after the other ! Babe Bee .049 This Site Rocks! bounce
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Post  layback209 Sun Nov 21, 2021 8:46 pm

Hi everyone I was able to test some engines today Very Happy.

It was brisk, about 0 to 2 degrees Celsius out. But no wind.  I ran the 1st engine (top one of the 0.051s) and the medallion 0.049.  Was only able to do 1oz per engine with the time I had.  

Fuel was 25% nitro sig 1/2a fuel. 2 head shims on the TD, 5x3 prop, and TD high compression head. I'm running them at about 1km above sea level.  

The TD happily swang the 5x3 at 22,xxxrpm peak, and was pretty steady at 21.5k to 22k. I'd say a successful rebuild.  Small Cox Logo needling wasn't the greatest, but I think the cold influenced that a bit. Going to try 3 head gaskets next time and see if it makes an impact on starting easier. Again started with a week glow igniter, swapped to my back up and it came to life.  It's a ripper and a half cheers

The medallion is a real sweetheart, easy to start, needled well.  Used a standard head with 1 head gasket.  
It turned a 5x3 at 18k rpm happily.  Peaked some where about 18.7 rpm.  

I'm very happy with the results so far.  

Which teedee will perform the best?  Videoc11

Which teedee will perform the best?  Videoc10
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Post  getback Mon Nov 22, 2021 6:49 am

That sounds Great ! Good numbers with the fuel and prop setup , Yea I personally like the Medallions better because of the easy stat and needling and the power output is right there with the TD s Small Cox Logo Good job on the rebuilds ! Very Happy
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Post  cstatman Mon Nov 22, 2021 9:16 am

i see a vintage suzuki and a proper lathe.

Waiting to hear that you are turning parts for the cox motors!

Smile

good work, love the renovation
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Post  layback209 Mon Nov 22, 2021 1:36 pm

Thanks gents, I re-read a TD manual I have. It's amazing, no matter how many times I read those things I always pick up some new detail.

Good eye cstatsman. That is indead a older Suzuki TS185 oil injected 2-smoke.  It's been a 10yr project and counting.  I am building it up for the vintage motocross circuit in Alberta.  New top end, almost to max jug bore now.  Got one step left.  I  went through the engine, every bearing replaced, minus the big bottom as that was still in spec.  I've definitely downsized over the years, I was up to 6 bikes at one point.

Haha yup the lathe is destined for nitro stuff.  I'm almost done repairing it, been in the family since the 60s.  I'll be hopeing to cutt proper bushings for 1/2a apc props soonish.  May turn some different TD venturies, make some mandrels for building tuned pipes.... it's also been a 3yr project.  When my kids are a bit older they can help me Very Happy maybe. Always a challenge to balance your time for those hobby things.

Here is what I dug out of the manual; looks like we are right on manufacture specs. Perhaps a bit better.  Didn't realize that peak HP was at 22.5k.  That's interesting.

I always struggle to balance 1/2a props, the top flight magnet balancer doesn't seem to work on them.... end up making them out of balance by default. Once the shaft is magitized it stops at the same spot so you end up balancing the tool and not the prop.  Not an issue on larger props mind you.  I picked up a dubro one to try out.  The TD liked the cox 5x3 more than the apc 5x3. The apc was probably a bit out do to my bushing.   I'll try some brass tubes to see if I can get it better for the next runs.  Or dig around for a Cox "grey 5x3"

Which teedee will perform the best?  20211112

Which teedee will perform the best?  20211111
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Post  balogh Mon Nov 22, 2021 1:53 pm

The COX props are really indestructible but they flex and lose pitch at high speed. APC props snap easily if you land nose down but are aerodinamically better and do not flex. I still love the black 5x4 COX props on my 049...051 TeeDee-s better. RC Plane
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Post  cstatman Mon Nov 22, 2021 4:07 pm

had a GT185 for a while. Smile

get that lathe going! gives ya something to teach the kids

APC prop bushings sounds like a solid project. as mentioned, stiffer, snap on landing, but holds power....
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