tank placing

thank you...that helps a lot...I have another question you may know the answer to...I recently purchased a TD 051 on ebay, the brass collar that mounts onto the crankshaft ? is that supposed to press into place and lock the collar from moving ? the teeth seem pretty warn on the crank that grip the collar, I can't seem to get the prop tight...maybe it's a spacing issue and I need a bigger fiber washer ? i'd appreciate any help you can offer, thanks- dave

What I have seen in the past is when an electric starter is used it pushes the driveplate into the crankcase and grinds some of the crankcase away. If the back of the driveplate has a ridge/groove then that is more than likely what happened. There should be a phenolic washer between the two,but sometimes it gets removed by a PO.

As long as the drive plate does not spin you should be ok although, replacing the driveplate is cheap insurance.

As far as endplay is concerned don't be too worried as the prop pulls the driveplate away from the crankcase when running as well as the crank away from the backplate. OTOH installing an extra washer does not hurt anything either.

Hope that helps,

Ron

that explains the design a bit...but is it normal to have a hard time getting the prop to seat tightly ? and trying to get it located so it's straight with the leading edge (on compression ) is impossible because I have to just keep cinching down the prop...I feel like i'm missing something...

Is it possible that the screw thread in your crack shaft or the thread on the propeller bolt is nackered?

Lieven

You may want to look into what Lieven mentioned. I find it's trial and error to get the prop seated where I want it. The screw wants to turn the crank away from compression.

Is your prop hole the correct size?

Funny, they don't move much for me. I grab the prop firmly, put a finger on the drive plate. Tighten the nut up and locate the prop as desired, then putting some pressure on the drive plate and holding the prop firmly tighten the nut.

.049, .15, .35, .40 - all the same really

Yes, sometimes it wants to walk out of position, but this is not the normal. If the hole is catching on the threads it is worse.

Phil

the brass back plate, I think Rusty had mentioned it, is wore out and doesn't catch on the crank...i'm thinking of scribing the back side of it and turning it around ? or should I find another...plus i'm not altogether sure it's brass...also does anyone know the proper placement of the small cox tank pictured above ?

 The crank plate only gets "worn out" by being removed from the crankshaft and put back on.  Several times doing this with or without carefully lining up the splines and the hole in the plate is opened up.  (once without can do it)

I have a couple engines that have worn out holes and they tighten up fine.  Putting a dab of lock tite onto the crank can help.  Be careful not to get the lock tite into the bearing (the front of the case).

If the plate is wore out you can order a new one from Bernie
http://coxengines.ca/
or Matt
http://www.exmodelengines.com/

Both their sites are organized similar.  Go to ".049 and .051 parts" => "front end" and select a drive plate to order.

The new drive plate will not have splines for the crank.  These are "cut" by the crank when the plate is installed.  Since I doubt you have an arbor press available, you use a stud and spinner nut with a spacer like a prop to press the plate on straight.  Put the stud in all the way, then the plate goes on, then prop and start tightening the nut till it bottoms out.

Phil

On the tank use your fuel ball (syringe) to put a small amount of fuel into the tank. Apply suction to the single line and learn where the fuel pickup is located. The fuel pickup goes to the outside and back. I expect the fill and vent lines are also to the outside.

Locate the tank on the plane so the CG of the system is where it is supposed to be without fuel. Fuel will move the CG forward which will increase stability and reduce responsiveness. However if when nearly out of fuel the CG is too far back the plane will be unstable and not controllable.

The tank is probably going to be on the center line of the airplane, or just outside of the center line.

Square tanks like that can be located slightly diagonal (0-5 degrees) so fuel is forced to the fuel pickup location by centripetal force. Platter planes generally fly with quite a bit of "out" trim so you may need to increase this if the tank won't run out.

Before you mount the tank it is a good idea to use your fuel ball and apply pressure to the tank with the vents covered and the tank in a sink of water to check for obvious leaks. You may need to flush the tank with fuel after to remove any water.

Phil

very helpful