WTB: Testors Pipe Bomb Crank

A very common problem with those engines. Ken

Cribbs74 wrote:That sucks.... I'll trade you a whole pipe bomb for an certain engine mount. 

Ron, I think you still would need to pay me   

Ken Cook wrote:          A very common problem with those engines. Ken

Is it the crank-pin that shears?? I've heard that they're pretty good runners... and maybe using too high a nitro content causes this?

This one had a stuck piston and I got it to free up, and kept turning it till it broke

WingingIt74 wrote:This one had a stuck piston and I got it to free up, and kept turning it till it broke

That's a bummer... sorry Travis. I know this is "after the fact"... but if you have another stuck piston in the future.. remove the back-plate and gently pull the connecting-rod off the crank-pin first... "then" remove the cylinder from the crankcase, remove the glow-head and soak the cylinder in a solvent (overnight.. if you have time). Use a small block of wood (cut approx. 1" x 1")  and bore a hole "straight through"..  just big enough to thread the cylinder into it.. until it stops snug on the shoulder. MAKE SURE there's clearance for the connecting-rod. Obtain a hardwood dowel closest to the diameter of your cylinder's bore, and "squarely" cut it to approx. 1" long. Oil the cylinder-bore, and center the dowel into the top of the cylinder and use a vise or C-clamp to put slight pressure on the dowel/piston and wood-block; to push the piston downward... being careful not to bend the connecting-rod. If the wood-block is thick enough; bottoming/bending the rod shouldn't be an issue.

I guarantee you'll never break a crank/pin doing it this way.

I did that and got it free, cleaned it all up, was fine till it got close to TDC, then the piston got stuck. I figured it would be ok just to force it though... wrong, the pin on the flywheel part of the crank broke. Being my first experience with this brand of engine, not too thrilled.

WingingIt74 wrote:I did that and got it free, cleaned it all up, was fine till it got close to TDC, then the piston got stuck. I figured it would be ok just to force it though... wrong, the pin on the flywheel part of the crank broke.  Being my first experience with this brand of engine, not too thrilled.

Wow... I'm a little surprised that happened. There must have been a carbon-ridge on the cylinder-wall just below TDC, which is probably where the piston was stuck???

I just put a Cox engine together a couple days ago, with a cylinder that I "knew" had a burr on the cylinder-wall at an exhaust-port (probably caused by a Cox wrench) I had nothing to lose.. so I lightly took a small 1/2-round file to it, removed the burr, used some 320 grit paper to clean it up, swabbed it with rubbing alcohol and a Q-tip, until the piston would pass cleanly through... oiled it up, assembled it... and it started easily and ran fine... go figure.

I should change this to "Free to a good home"   

Don't write the brand off because of one experience. We all know that Cox engines sometimes break the crank pin when put under pressure, yet we still persist with them. I suggest he crank must have already been fatigued to break with hand pressure. I did have one break on me while running early in the engine's life. A used replacement crank run under the same conditions never gave a problem.
It won't be hard to find another crank. I may even have a spare but would be cost-inhibitive to send it from AU.

Rod.

If the pipe bomb car crank is the same I have one you can have. Just missing the glow head.