crankcase crankshaft fit

The HD crankshafts that were used in the Venom and Killer bee were a slightly smaller diameter than the stock crankshaft. It was to reduce friction.

An anodized case could conceivably be slightly tighter than a plain case. That's assuming the coloring material has any thickness above the surface of the aluminum. Anodized bearing surfaces are said to have lower friction, but that doesn't mean they can't have less diameter. Just guessing.
Rusty

EDIT: Jason to the rescue.

I picked up this KK crankcase at auction a few weeks ago (who was I bidding against) and found a standard crank fit is very loose, much less a KB crank.
Also there is no oil groove. I have found when the crank gets too loose there is too much vibration when running.
It has a oolite bronze insert, anyone ever use one of these before?

I've read about some of our CEF guys putting bushings in them, but I don't recall who.
Rusty

crankbndr wrote:I picked up this KK crankcase at auction a few weeks ago (who was I bidding against) and found a standard crank fit is very loose, much less a KB crank.
Also there is no oil groove. I have found when the crank gets too loose there is too much vibration when running.
It has a oolite bronze insert, anyone ever use one of these before?

The KK catalog lists a crankcase (their part# 234) stating having "a special full-length oillite Bronze bushing to prevent the common problem of galling between the crankcase and bearing journals" It was a separately available part, along with their part# 231 "Specially Heat-Treated Crankshaft, tempered for toughness".

These parts were an assembly that was included in their complete Cox Reed-Valve .049 engine (their part# 201) modified for class 1 Mouse or scale racing. This engine also featured a "Custom" .049 Tee Dee cylinder/piston and rod assy. (their part# 049C) which had "modified transfers and timing for increased performance".. a Tee Dee glow-head, a custom 8cc tank and a custom back-plate and needle valve assembly (their part# 232) with enlarged venturi and a fine-thread, precision-taper needle valve with collet type locking nut that prevents drifting of a needle setting.

This engine was also available as part# 201Q... which featured a modified 8cc tank for "quick filling" (part# 235) using their Quick Fill probe (part# 236)

I would imagine that Paul G. may have experience with these KK engines/parts.

Wow, you have the KK catalog? Sure would like have one of those #201 engines.

I am pretty sure Ken has some of those cases or has built some on his own.

Roddie, how big is that catalog? It would be nice to have a copy of it stickied on here.

Ron

crankbndr wrote:Wow, you have the KK catalog? Sure would like have one of those #201 engines.

Yea.. I have a catalog. I never ordered anything from it though. The catalog is postdated 1993. I keep it in a 3-ring binder with all my other model papers. It's fun to look through and dream about what used to be available for your Cox engines through them. I should scan it some day... along with my other old modeling documents.

Ron, I'll make a point to scan it. It's 7 sheets (8-1/2" x 11" double-side printed) that was stapled in the center.. to make a 14 page booklet.

I have one of the bushed cases like
yours Roddie, with the heat treated
crank. Ordered from Joe Klause over
the phone in 1981. I also have a couple
of the fine thread backplates.
I dream about this stuff too.  
Bob

I was really using much of my Cox items pretty hard and daily prior to Estes ownership. This is when things started going haywire. My son and I were essentially flying the same planes therefore a lot of stuff was run double hard. The end result was a lot of broken parts and worn out crankcases. I couldn't keep a crankcase fit due to them wearing out as mentioned. They would wobble and resonate in the case and this really robs the rpm's. When the fit is too tight, the engine also suffers in rpm's. The problem is just when the engine really starts to perform, it's on the edge of it's case being worn out. I got together with my friend Dan and we started to bush some of the Black Widow cases. This works exceptionally well and the engine really runs noticeably smoother. We were fortunate to have a friend who rebuilt his Ferrari. He gave us the old valve guides which is what we used for bearing material. Dan has done many Fox .35's with those valve guides for us in the club due to the case bearing wearing out. Talk about lipstick on a pig.

The mouse racers used the bushed cases and this really gives the engine the longevity it deserves. Ken

Installing that bushing isn't really all that hard. I have to wonder why Cox didn't do it in the first place. It would have made a world of difference. I suppose with normal use the engines were fine as is, but once pushed past their envelope they wear quickly.

Aluminum by itself is a good bearing material, at least until grit is introduced. It then works like a lapping compound hence the black oil. You do however need the proper aluminum for longevity. The material that Cox used for the case wasn't that material. It worked for it's intended purpose to be extruded and for machining rapidly, but it lacked in it's durability. These were inexpensive engines which worked. The engineers were well aware of that and the bottom line is that you only make things last as long as they need to. Make them last long enough to buy another.  In my situation, I purchased a reamer which was expensive. The first few cases we did we ground a boring bar to fit into the case. This took a long time to machine the inside diameter. The bar is so narrow that it wants to flex during the cutting. The reamer resolves that issue. While it doesn't mean you just slip the crank and go run it, We had to get a little higher tech. We used a piece of drill rod with sandpaper glued to it for the final fitment.

I would like to make some more. I got to the point that I was switching so many items from one engine to another I don't know what was the original. My advice is to use that KK case and enjoy it. They work well. Ken

It has a oilite bronze insert, anyone ever use one of these before?

Hi Guys, the answer is...maybe. I do have one of these bronze bushed K/K cases. When done RIGHT, I believe the shaft to c/case fit becomes stable & the engine may not necessarily run any faster at all, but it will have a substantially longer running life. On his complete K/K engines, I saw a number that ran really well. Mouse master John McCollum also bushes his own custom Cox engines which run particularly fast & stable. So, done PROPERLY this is a good modification.
That being said, I've never used one on any of my own engines. I've personally found that the color anodized cases with the Killer Bee type crankshaft work as good as anything. Both Killer Bee Gold, Venom Red & Black Widow Black cases have all performed identically. I have not paid attention as to when or if my c/cases are worn out. If the anodizing on the inside of the case becomes galled or worn, I replace the case just on spec. As long as the crankshaft spins nicely in the case when perfectly clean, I call it good. Evidently though...some are better than others performance wise, but I couldn't tell you by how much. I assume the c/case wears & the steel c/shaft does not. But, I haven't developed a way of mapping out the parallelism along the entire bore of the c/case. Nor have I found a way of determining that a particular fit is too loose or too tight for that matter. I've not measured the difference (if any) between crankshaft diameters either.

I will say that I do have one K/K bushed c/case in my possession. I was really miffed to find out that that particular c/case ran 2,000 RPM SLOWER than stock standard. It's c/shaft fits beautifully & it's nice & free. BUT IT'S ABSOLUTELY SLOWER! My choice now is to either try to decrease slightly the diameter of the c/shaft OR increase slightly the bore of the bronze bushing. (I'm only assuming the fit is too tight rather than too loose here)

I took the (mentally) easy way out & tossed it back into my quarantine slow parts bin, awaiting the day I may be interested in playing further with it...

So your answer.... it could be as fast as stock new parts, but it might be noticeably slower too! I only wish Joe Klause was around to tell us why he did it & more importantly...how. Best of luck guys!

Cheers, Paul