Restoring a rusty engine

Not sure how these will look (first time uploading pics to the site). If this doesn't work, I have posted the pics to my personal gallery.





Is that the stuff we lovingly refer to as 'naval jelly' over here? Phosphoric acid based?

Decided to open it up to take a peek inside. Popped off the back cover and glow head.

Inside of the cylinder and top of piston are brown and dry. Not as coarse as the outside, just light rust. Hopefully some oil and steel wool will clean that all off. Only shiny parts are the back of the crank rod pin and the inside of the backplate. As if the spinner wasn't a good indication, can you say 'abuse by starter'?

Here's the really disappointing kicker. I ordered two 09 wrenches from Bernie, and the open end doesn't fit the flats on the top of the cylinder (opening too small), or the exhaust ports (too large)! All I could use it for was removing the head and backplate.

Did manage to remove the cylinder using a kitchen rubber grip (for opening jars). Piston rod socket has surprisingly little play. Can't get the crank to release from the driveplate - neither blunt force coaxing, nor a squeeze in a vise would do it, even with some penetrating oil. May just have to let it sit for a while, or heat it up.

More later.

Question: With the venturi body locked on there, how high a temp can I safely heat the crankcase up to without damaging the delrin?

I think your on the right track with fine (0000) steel wool and a light cutting oil, but be careful. You can remove all the finish on the cylinder with 50/50 vinegar or muratic (sp) acid the reblue with a quality (Brownells Oxpho) gun blue. I did a thread on this sometime ago and when finished you cannot tell from new.

Bob

VUgearhead wrote:... Can't get the crank to release from the driveplate - neither blunt force coaxing, nor a squeeze in a vise would do it, even with some penetrating oil. May just have to let it sit for a while, or heat it up.

More later.

Question: With the venturi body locked on there, how high a temp can I safely heat the crankcase up to without damaging the delrin?

Try removing the prop drive plate by turning the threaded collet counter clockwise with the wrench, as if you simply wanted to remove the collet. I managed to remove prop drive plates this way on many engines without killing the drive plate or the collet..

^ That has worked well on all my .049s, but on them the fit is quite loose. I don't know if the .09 has a tighter fit, or maybe it is rusted? Anyway, be careful and apply some oil into the threads before turning the collet.

Penetrating oil requires some time to work, so maybe if you soak the prop plate area for a few days, it will have time to work. Heating the plate might be a good idea too.

Good luck

My method:
Cox wrench side ways on a vise so that I can bear down while removing the back plate....most of the wrenches are same width as the two cut outs in the back plate

Heat gun the cylinder very very hot to use same wrench to remove the glow plug, hopefully with OUT the cylinder

Same very hot to use same wrench across the exhaust and get the cylinder off most of the time sliding the rod aft and cylinder and piston are still mated

Heat again and start backing off the crank case front venturie holder to force propeller drive plat forward and off

Heat again and with fingers/hands wiggle delrin venturi back and forth to come forward and off

ON a really cruddy one I crock pot in anti freeze first for a few hours

Just well worn with castor crud I soak over night in Hopps #9 cold

Gun cleaning boar brush the right size in the cylinder ...not a lot...just scuffing and removing some of the crud

Scotch green pad slice to remove crud from outside of piston skirt and inside the cylinder a few strokes

Nylon tooth brush, then brass, and then stainless on the back plate threads and cran nose threads

Drop all the part in a ultrasonic with simple green and water mix for 30 min

Spray cheap brrake cleaner on all parts

Follow up with a sprits of WD-40 (remove any water I don't see

Reassemble and use Marvel AIR TOOL oil

Feed with 25% Sig and start

Drown in 90% denatured alcohol... blow out with compressed air.....a few drops of AIR tool Oil and put away until plane is ready

On one or two I needed to use a leather piece and vise grips to get the cylinder to let loose but I try to avoid this on thin walled cylinders

A few years back the Cox bug bit but sticker shock set in so I bought a LOT of junk LOTs and managed to turn every bit into a working engine

I have 10 TeeDees and 7 Medallions ..... mostly rebuild from parts and they all run very well ....each needed a bit of coaxing to be re-furbished

Just sent my last 2 TeeDee .09s to Bad Bill... I bet if you asked him he would not describe either as a trashed basket case....but trust me they were pretty shabby when I got them

Solvents
heat
Brute force
correct lubes

I have never found a Cox engine that could not be rehabilitated

I just want to give you a friendly reminder, as I would hate to see something happen. Please make sure that you remove the piston/cylinder BEFORE you try to remove the crank and driveplate. I know you said that you already had them off, but this is just as a reminder as I was too in the situation a month or so ago, took it off, put it back on, then was wondering why my crank and driveplate was being difficult. My piston could now tell you why...

I tried pushing the driveplate off by backing out the collet nut. I torqued it so hard, I was afraid I was gonna snap the backend of the crankshaft off. Wasn't easy easing it back off either. So....

got the front end drenched in liquid wrench oil right now. Will try heat application tonight. I looked up delrin (aka polyoxymethelene), melting point around 350 deg. Farenheit. Maybe put my solder iron to the driveplate, then see if I can tap it out.

Dan

A damp paper towel wrapped around the plastic will protect it from excessive heat. Derlin can take a fair bit of heat without problem though. That is no reason to risk heating it up more than necessary.

Phil

Dan,

I am not a big fan of using the collet to drive off the drive washer. Those puny aluminum threads are easy to strip, plus the twisting force against the plate does nothing good for either part.

Take the backplate off. Screw the prop screw back into the crank, lay the crankcase on a hard surface and tap the prop screw with a hammer. It will come right off.

A bench press is the best way to go if you have one.

Cribbs74 wrote:Dan,

Take the backplate off. Screw the prop screw back into the crank, lay the crankcase on a hard surface and tap the prop screw with a hammer. It will come right off.

A bench press is the best way to go if you have one.

One thing I do when using the prop screw, I leave a plastic prop on, and back out the screw a couple of threads at a time as I tap the prop screw. That way there is minimal chance of bending the prop screw as you tap.

The Screwy Mark

batjac wrote:

Cribbs74 wrote:Dan,

Take the backplate off. Screw the prop screw back into the crank, lay the crankcase on a hard surface and tap the prop screw with a hammer. It will come right off.

A bench press is the best way to go if you have one.

One thing I do when using the prop screw, I leave a plastic prop on, and back out the screw a couple of threads at a time as I tap the prop screw.  That way there is minimal chance of bending the prop screw as you tap.

The Screwy Mark

Darn, thats a great idea. Simple, yet effective. The past few times I removed the driveplate, I was worried about bending or breaking the screw. This will definately help. Thanks for the tip.

Cribbs74 wrote:Dan,

I am not a big fan of using the collet to drive off the drive washer. Those puny aluminum threads are easy to strip, plus the twisting force against the plate does nothing good for either part.

Take the backplate off. Screw the prop screw back into the crank, lay the crankcase on a hard surface and tap the prop screw with a hammer. It will come right off.

A bench press is the best way to go if you have one.

and always try to use a hardened screw or bolt. Standard screws-bolts can take a few wacks with a hammer, but a 80 hardened screw-bolt, available lots of place including Bernie and Matt, will handle the repeated used a lot longer. I use a dedicated crankshaft removal tool, hardened screw and spinner adapter, which is made for the job.

like this: http://www.ebay.com/itm/049-051-Model-Engine-Crankshaft-Crankcase-Crank-Assembly-Tool-for-Cox-049-051-/370565487223?hash=item56476c9a77:g:BSsAAOSwiCRUbN6H


Cox Crankshaft removal tool, for me   $2.95

or this one:
http://www.ebay.com/itm/COX-ENGINE-049-crankshaft-removal-installation-tool-/281011494961?hash=item416d972031:g:sPQAAOSw1S9WfFNw


Cox Crankshaft removal tool  $3.99

or this one:http://www.ebay.com/itm/049-051-Engine-Crankshaft-Crankcase-Crank-Dis-Assembly-Tool-for-Cox-049-51-/370565487213?hash=item56476c9a6d:g:zI0AAOSwfcVUHLWo


Cox Crankshaft removal tool, $2.95

Nothing personal to either company. Both products are great.

edited 9p.m. PST 2-24-2016 to add another tool.

happydad           

Cribbs74 wrote:
I am not a big fan of using the collet to drive off the drive washer. Those puny aluminum threads are easy to strip, plus the twisting force against the plate does nothing good for either part.

That is correct. If you do this, use just a minimum amount of force, don't put the engine or the tool into a vise or anything. Just bare hands, and not all your force.

Cribbs74 wrote:
Take the backplate off. Screw the prop screw back into the crank, lay the crankcase on a hard surface and tap the prop screw with a hammer. It will come right off.

A bench press is the best way to go if you have one.

That's the method I use for reedies, and it's a small hammer. A press would press straight but with a press it is easy to create a force that may distort something if one is not careful. I don't have a press myself, but if I had, I think I'd still use the hammer and a block of wood.

About the assembly tools, I don't have any yet, but one thing that I don't like about them is that you need to turn the stud in the thread of the crankshaft to pull the prop washer on. This will cause unnecessary wear on the thread. It would be better if there were a stud that you screw all the way into the crank thread, then put on the prop washer, propeller, another thick washer and then use a wingnut or a standard nut to pull the assembly together. This way all the wear or mishandling would happen to the stud and nut, not to the crank thread.

I certainly appreciate everyone's advice on this.

Tapping (gently at first, not so gently by the end) on the prop screw was the first attempt I tried. When that proved fruitless, I went to my bench vise. Even torquing the c'shaft/driveprop in that didn't budge it. By this point, even with a folded papertowel as protection the head of the prop screw has flattened out. It still screws in/out just fine tho. No evidence of warping.

I then tried backing out the collet nut, just by holding it in my hand and using a wrench on the nut. Again, torqued it so tight against the driveplate, was afraid I would pop the backend of the crank off.

That's when I figured heat was my last option.

Well, tonight I tried to use the heat method. I applied my pencil solder iron to the driveplate, enough until it was too hot to the touch. Still hammer taps (then blows) did not budge the driveplate. I then went to my bench vise and again tried to use it. No joy.

Both the collet nut and prop screw still move with ease. If I didn't know any better, I could swear the driveplate was epoxied on there!

I may have to take Matt at EX Models up on his engine rebuild. Got no other choices. No crock pot for cooking here.

Dan

But I had to whack that prop screw harder than I ever wanted to to get that sucker loose. Don't know that I'll ever trust that prop screw again.

Now to commence to cleaning!

yay i can't wait to see this sucker run!

Here is an exploded view on my kitchen table. Still working on my photography skills. Hopefully you can see the exterior cylinder rust, the crankcase interior, and the scrape marks on the inside of the backplate.

nice!

[quote="VUgearhead"]Here is an exploded view on my kitchen table. Still working on my photography skills. Hopefully you can see the exterior cylinder rust, the crankcase interior, and the scrape marks on the inside of the backplate.

quote]

Congratulations, it is good to see that all original parts have been saved. How about the piston/cylinder fit, does it provide a good compression?

I did not turn it over to check compression, given the rusty nature of how it was received. I tried to move the piston as little as possible to avoid any scoring of the liner.

Not sure about the glowhead either. I haven't heated it up to see if it glows. But I have a couple of extras in case it doesn't.

Dan