End play/ Cox.049 prop size for Gentle Lady

[amike_321]

I need to know what prop size to run with a cox tee dee .049 on a Gentle Lady Sailplane. I also have a question about the end play when wiggling the prop nut front to back. It looks like I have about enough to stick a fingernail in. This may be normal but I have no experience with Cox engines.

[Remby]

Hello,
I would suggest starting with the 6-3 . That should give good flights. On your endplay, have you looked inside at the Backplate? I think if it shows scrapes from the piston rod/ crankshaft, it needs the front hub tighter. However, the ammount you describe sounds about right. Perhaps another can add extra info, I don't think you have any major problem there. Hope this helps!
Best,
Remby

[amike_321]

Yeah i opened it up but everything is clean as a whistle, no scratches. I was just curious about the clank it makes while holding the case and pushing and pulling on the prop nut. Its probably okay but i wanted to check. Thanks

[Remby]

I would say it will work good for you then, good to hear of you checking the inside as this is really what to look for. These engines are great and should give you good flights. Let us know how it goes!
Remby

[BMatthews]

That end play is quite normal for an older model of TeeDee or any Cox engine for that matter. Later versions that were set up to allow frantic electric starter use have a little blued steel shim between the prop driver and the case to act as a bearing plate and prevent galling between the two aluminium parts and also prevent any possibility of the crank pin scoring the back plate.

Even if your's is a newer one some previous owner may have removed the stell shim.

In all of our plane bearing engines you want to be able to feel a little float. That way when the cranckcase heats up and expands more than the steel crankshaft there won't be any binding.

[amike_321]

It does look like there is some kind of spacer there between the case and prop backing plate. Thanks. Im starting it up this afternoon, hopefully it wont go Boom!

[amike_321]

Well I got everything lined up tonight and went to fire the ole motor up. i was using a wooden dowel to flip it over and I mistakenly broke the carb base, you know the plastic piece the carb screws into. I found a parts list that came with the motor. Has anyone ordered from Cox directly. Or better yet does anyone have a used one that I can buy? Help!

[Remby]

Sorry to hear of the damage. Cox sells these still, at least that was the case last I knew. You could also look to Ebay, lots of parts for the cox stuff.
Remby
.

[BMatthews]

The last I heard those case parts weren't cheap.

When you get it back together I strongly recomend the naked finger approach or at most a leather glove to avoid the same thing again.

If you sand the burrs off the leading and trailing edges of the prop it won't cut or at least not cut as deep. And a little "negative reinforcement" is a wonderful stimulation towards learning proper flipping habits...... :D

[amike_321]

I dont want to be near anything thats spinning at 20,000+ rpm. I'll probably get a fuel line to make my adj on the needle.

[Remby]

Yes, these engines can give some nasty tatoos, if you run them enough, it will find a way. Always good to keep some first aid with you, at least som form of bandage just in case.

[amike_321]

Got the throttle body that was damaged repaired. I ordered another straight from Cox. Seems my glow head was bad also, since I installed a new one, it fires up and runs like a champ. I probably have about 25 minutes of break in time on this .049 monster. Oh and the prop rpm, yeah tested it with my finger. it was spinning pretty fast. It left a nice tattoo:)

[Remby]

[i]. I probably have about 25 minutes of break in time on this .049 monster. Oh and the prop rpm, yeah tested it with my finger. it was spinning pretty fast. It left a nice tattoo:) [/B]

I never thought to test the RPM with my finger, glad someone else thought of that!

[T. Lyttle]

Heehee! Welcome to the Cox Owners Club! Gloves are the best way to deal with them for starting, but adjusting the needle takes practice, and lots of it. The bandages are a recognised part of the Cox Tool Kit, but not always listed...

HOwever, if the cuts interfere with your piano practices, we do see your reluctance to sacrifice your flesh to the little beast.

BTW, what "breakin" procedure are you using? Sloppy rich, I hope, until the cylinder is too warm to hold onto, shut down, allow to cool, repeat. I've broken in Cox engines that way, and they have lasted for many years with above-normal performance...

[Scratchbuild]

Hey amike_321,

I also have cox tatoos. The break in shown by T. Lyttle is a great way to do it. I am still flying some engines I bought in the 60's.

I tried several props on my Gentle Lady.

The best prop for the cox .049 in any plane is the APC 5.7 X 3.
This is a strange size. The hobby shop had to order it is lots of 12 so I bought all 12. It turns an .049 into a real screamer.

It is thinner than a Master Airscrew 6 X3 so watch the tatoos.

My cox engines have the flip back started springs on them. You have to watch the bend on these springs. If not bent back once in a while, they end up hitting the prop.

On engines without the spring, I wear a leather glove. Or as Red Green says, " If you forgot your glove, you can wrap duct tape on your fingers for what will be the cut."