• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.

Cox .049 Model

#1
Has anyone put a Cox .049 on a foamboard model yet? I've got two working ones laying around and haven't decided on the model to put them in. I'm basically looking for a stable and robust flyer that can carry a small nitro engine.
It should be fairly easy to repair and doesn't need to be very aerobatic or speedy.
I think a 'Simple' or bigger 'Mini' size plane should be good.
Thank you in advance for your hopefully very good advice.
 

Javiester

Elite member
#2
I have one and I have no idea how to test it and what precautions to take before trying it
I haven't touched it since they gave it to me
It was from a circular flight Stuka
I would appreciate indications
 
#3
I get all my supplies from coxengines.ca
They have literally every replacement OEM and new parts for all Cox engines.
For now I have three of the small .049's all only run on a test stand but never flown by me.
That's why I originally started this thread but no one seems to care about old nitro engines.
 

Piotrsko

Master member
#4
Not all parts, my .09 td has limited support and the .15.........well, lets just say orphan.

There are people that have built FT brown FB & report it is fuel proof. Styrofoam is kinda fuelproof but not fireproof.

IMHO for a 3 minute unthrottled run they are great but they can have throttles now and run from remote tanks.

I like to run them except for the goo and the pissback from the neighbors about noise. I have maybe 15 complete.
 

Bricks

Master member
#6
I use Windex with Ammonia and paper towels, or any glass cleaner with ammonia. You really need to make sure the firewall and associated parts are fuel proofed, I use Epoxy thinned with Acetone or Lacquer thinner just thin enough to be able to brush it on. It does slow down the dry time.
 

L Edge

Elite member
#7
One concern I have is mounting the engine upside down. What about hydraulic lock? These engine slobber while trying to start, so if fuel(also head pressure from tank dribbling possibly getting in) gets trapped and the piston goes down, it might bend or break the connecting rod.
Found that out by 049 up regular and using an electric starter, bent the rod.
 

TheFlyingBrit

Legendary member
#8
I use Windex with Ammonia and paper towels, or any glass cleaner with ammonia. You really need to make sure the firewall and associated parts are fuel proofed, I use Epoxy thinned with Acetone or Lacquer thinner just thin enough to be able to brush it on. It does slow down the dry time.
Fibre glass resin also works well to protect the firewall.
 

TheFlyingBrit

Legendary member
#9
Ive x3 049's and flown them many times but never in a foamboard model. Firstly the castor doesn't burn off during combustion, so it sprays out with exhaust gases. As there isn't an exhaust to divert the spray and exhaust gases it will end up all over your model. That is the first problem, the impact of castor oil on the paper which will ultimately peel off when it de-laminates.
Secondly as careful as you are, there will always be some neat nitro fuel that will make its way to the foam itself. Being predominantly methyl alcohol (methanol), with 10% nitromethane. I am not sure what the impact over time will be on the foam itself, never got around to testing.
Most scratch builders use corflute for building nitro planes, corflute is a corrugated plastic sheeting around 5mm thick thats impervious to nitro fuel. Ive seen models built with this material, in combination with square plastic sections of drain pipe or aluminium tubing.
https://www.google.com/url?sa=t&rct...=f_ZvHeOnmeI&usg=AOvVaw1KzkKyCUg3JyGT3bWtym68
1608661378268.png
1608661457352.png

1608661599050.png
1608661436397.png

Some examples of Corflute models and what it looks like.
 

PsyBorg

Wake up! Time to fly!
#11
I'm going to try it the traditional way, balsa
mine has an external tank
View attachment 186833
I have given it a layer of filler
how do you clean fuel from the fuselage after flights?

Soft soapy water made with dawn dish detergent will clean it up nicely.

May I also suggest you also invert the motor? The way you have it mounted will waste fuel and probably flood the motor out. These work by filling the crankcase with the oil/fuel mixture and vacuum pulls the fuel up into the cylinder thru blow by of the piston. Inverted like that makes gravity flow fuel into the head at all times and not just on the intake/compression stroke.
 
#14
Soft soapy water made with dawn dish detergent will clean it up nicely.

May I also suggest you also invert the motor? The way you have it mounted will waste fuel and probably flood the motor out. These work by filling the crankcase with the oil/fuel mixture and vacuum pulls the fuel up into the cylinder thru blow by of the piston. Inverted like that makes gravity flow fuel into the head at all times and not just on the intake/compression stroke.
Thanks a lot
really is what i need, tips and notations
I will turn it over, the engine has come out of a circular flight cox Stuka and originally the cylinder is laterally mounted
I remain open to any suggestion and it is welcome and appreciated
 

PsyBorg

Wake up! Time to fly!
#15
Thanks a lot
really is what i need, tips and notations
I will turn it over, the engine has come out of a circular flight cox Stuka and originally the cylinder is laterally mounted
I remain open to any suggestion and it is welcome and appreciated
What happens as they wear and break in the bottom of the cylinder is wider then the top to allow fuel to be pulled up out of the crankcase. As these motors age that evens out more and more so the top is less tight and the motor starts losing compression. That is why these motors have brass/ bronze sleeves. There are also after market sleeves that can be used for performance tuning.

Side mounted would be better then underslung but that would make the cylinder egg shaped over time. Vertical is best. You can also remove the base plate and turn it any direction to get the needle valve to face any direction you want. Just be very careful of the thin gasket between the plastic and the crankcase.
 

Bricks

Master member
#16
Coroplast was pretty popular at one time but the planes get terribly heavy, just an FYI coroplast is what many advertising signs are made of. That is what made them popular for a time as the material could be sourced for free. It usually came in 3mm and 5mm and there was some much thicker but was way to heavy for planes. The stuff works great if you want to make a snow skimmer or something similar, it also works great for snow ski`s for planes. Add a little heat and you can shape it into a ski shape easily enough.
 

L Edge

Elite member
#17
If you have the .049's, you can drill out the pressure fitting and run it to the tank. After the tank is filled, seal the fill line and with the pressure, it will run more smoothly. No air bubbles. Don't forget to balance the prop.

If you intend to make many runs with the engine, buy a piston reset tool from Coc and as the performance drops, you can take it apart and reseat it.
We raced the 049's with after a run or two, it dropped in rpm's. After reseating the ball, we shot for 22,500 RPM's which was Cox statement that max HP is developed at that range. Worked for us.
 

Piotrsko

Master member
#18
Ummm plastic crankcases for the TD series have the pressure nipple, metal crankcases like I have do not although I have heard of drilling the metal attached tank for one. Never had a piston pin issue on medium nitro fuel, just on both my TD's trying to go real fast and above 15% nitro. Did burn a hole in the .09 piston on 30%, but that was one exciting flight.

I also run mine inverted cylinder a lot and even with a muffler on, it's hard to hydrolock unless you drown it on prime.
 
#19
as I still cannot go flying due to the virus restrictions, I have been doing tests with the motor049 since I got the accelerator ring
I had to remove the starter spring because it was tightening the ring and locking it
but now when starting it with the finger sometimes it starts with the reverse turn, is it normal?
How much slack is normal in the piston and in the crankshaft?
they both have a little
 
Last edited: