Wobbly Crank

Marleysky wrote:3 am in the morning, worrying 'bout a wobby crank?  Well WELCOME to the Forum!  

Yup, goes to show @gvc fits in with the rest of us!



to the forum, gvc!

Marleysky wrote:you assumption is probably correct. do you have any other Cox 049 engines you can swap cranks and crankcases with to verify the slop in the journal?  do you know the history of your RR-1? Must have been run without proper fuel/oil mixture to wear that much off the journal, usually that is where castor oil congeals,  heats up and slows the RPMs down. I'm not a machinist, the closest thing I have to a lathe is a hand drill. I'm sure someone in the group could tell you if its possible to re-sleeve the crankcase. If I were going to run it, I'd find a substitute crankcase, or NOS replacement.

Personally, I don't have an RR-1, so can't contribute much regarding re-sleeving your crankshaft journal bearing surface. However, please give some time for the others to respond. Also, it would be helpful if people knew your approximate location, so they could steer you to someone.

There is another in this forum who also sells machined products for Cox and a few other half-A engines on:

https://kamtechnik.com/contact-us/

If he doesn't or can't do this service, may be he can direct you to someone who can.

Another place to inquire is at Stunt Hangar: http://stunthanger.com/smf/index.php

Again, welcome to the forum!

Thanks for the leads. I am in Northern CA.

First hello I think it would be impossible to do a buching to repair because the particularity of this crankcase would make it fragile or even detach a part of the front with the grooves this is the line in the piece it leaves very little material to machine Could be possible but not 100% sure It would be possible to make this feature on another crankcase with a swan neck and anodize gold color

I have already managed to repair one with a pipe cutter I have worn out the round cutting wheel and I have place tight on the crankcase then turned a few turns, tighten and repeating until the crank turns with a small friction restriction !!!! dont cut the crankcase
its this engine Look the front this is the result and i made it anodized

Interesting method. I noticed on my worn ones that the wear was on the bottom of the case at the back. The front was not too bad. Maybe a short bushing at the rear would not weaken the case too much. It would have to be machined in very carefully.

On the back i used the Ball reset tool tink or it was a tool box I'm not sure I remember I asked m'y self the question for a while the principle is to use a round object with a taper inside so as to crush the outline of the hole inside or it could be a punch to make holes in the leather I I don't remember anymore
I used a bit of all sorts of things until it worked After the anodizing it was tight I did a polish with car polish and a dremel tool To lap the crankcase and crankchaft To mate them perfect and i have To use two thrust washer on this one One is over the wide part of the crank and one on the drive plate spline as usual but this engine did not have it was very worn I also had to install a buching in the piston conecting rod

I somewhat resolved the wobbly crank by using a crankcase from my parts box. Thanks for all the responses.

I have to post a 5th time before I can use the for sale/wanted forum so this is it.

Well I bought a new in box Venom 2 from a oldtimer fellow C\L fanatic, and was intending to use it to power my girls Man Win trainer. Straight out of the box I noticed that the crankshaft was very wobbly, you could see with a prop on it that the prop tips would move 1\4" side to side. It was like a joystick, not to mention the thrust slop. I ponder it for a few days and concluded that maybe the Venom was manufactured loose for more power..boy was I wrong! I should have gone with my gut feeling to find another crankcase and crank even though it was brand new. I decided to start it, and on the third rich tank.it locked up..broke the connecting rod right where it connects to the ball in the piston..Crazy! Never in 30 yrs flying nitro have I seen a broken connecting rod.

I have had/seen a broken rod that went through the case of a TD, a rod that wore through the top of a piston in a swap meet motor, broken cranks at the crank pin.... Later cranks had a thicker web in the TDs and I believe the reedies too? Maybe your piston/rod socket was loose?

Hi All,
I had a pull start Cox Sanblaster rig,
To put on my new RC (Heathkit) equipment.
Good Luck,
Dave

broke a controd on a piston where it connects to the piston. TD at absolute full cry on 42 foot steel tent pegged Plane was a write off engine seemed surprisingly ok, quick cleanup disassemble on launch table and clean and into another plane. To my surprise started perfectly, ran great! Launched plane, flying around, all was good, and then silence. The engine just stopped.
Had a look, didnt turn over so good anymore.



Cant really blame Cox for that one though.

Yabby

Hi Gvc , there was a guy on here that did a repair on the journal with a valve guide from i think was a Porsche , so you said you were looking for someone I would try engine machine shop they do this work as in replacing guides and could possible turn on down on a lathe and press in in for a FEE ! Don't cost much to find out and beeing in CA. in am sure there are some good shops out there   And I would have sent that Venom back for a refund off of eBay as soon as i seen the slop !  Wow here is one for sale Bid > I would ask him what he means about the Bad crankshaft , Maybe the pin us broken the shafts very seldom wear out.  https://www.ebay.com/itm/266096417685?

Thanks getback - I contacted the seller with the RR1 parts, you guessed it, the crank pin is broken off. Thanks for the lead. I may bid on the parts and hope that the crankcase is better than mine.

Here’s my RR1 with a Babe Bee crankcase. It’s a strong runner with none of the finicky reed valve issues. It is a little hard to start requiring lots of primes.

Nice looking engine , may try a new/difft. glow plug and see if it starts easier . Those parts only come around ever few years from what i have seen ( just keep that I mind ) Is that old castor at the front drive plate ? Good luck if you decide to bid .

I suppose it is baked on castor oil. I bought the engine used and was disappointed with the worn crankcase. I think the buyer sold it in good faith and worked with me a little when I pointed out that the engine was unusable.

gvc wrote:

gvc wrote:Here’s my RR1 with a Babe Bee crankcase.  It’s a strong runner with none of the finicky reed valve issues.  It is a little hard to start requiring lots of primes.

[...]
I suppose it is baked on castor oil.  I bought the engine used and was disappointed with the worn crankcase.  I think the buyer sold it in good faith and worked with me a little when I pointed out that the engine was unusable.

In salvaging the situation restoring the engine to a great runner, I'd say that now you have a story teller. That hybrid engine, uniquely customized by you, restored to fine running condition is a potential winner for the next COX ENGINE OF THE MONTH CONTEST as is. But, you could possibly highly polish the Babe Bee crankcase to a mirror finish, and send chills up @fredvon4's spine.

Awesome setup you have there!

WOW it fetched a pretty good price >> https://www.ebay.com/itm/266096417685

I’ll say, I was stunned. It looks like I should be happy with the Babe Bee crankcase. Here’s another, I wonder if it will go for the asking price?

https://www.ebay.com/itm/115514154846