daven

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One of my Nelson Quickee engines has got a very slight grind in the front when I turn the prop. It just doesn't turn all that smooth like the rest of my engines.

I think its time for new bearings, and was curious if there is any advantage at all in going with ceramic bearings?

MikeyD

Dave
I would recomend you fly that motor as is this weekend at Rockford. That would give us slow guys a better chance, dont ya think??

Mikey D

daven

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Thats pretty funny Mike.

I'm only going to change them so I can try to keep up with you and Frazer.

Randy Smith

One of the guys in our district has been using the ceramic bearings in his 428 and Q40 engines. I will fwd this thread to him and he can comment directly. Look for Hank Kauffmann to respond.

Randy

Bill Vargas

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Dave, are you beating up on those slow guys again,,, hehehe

BV
NMPRA 41C

daven

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I'll look for Hanks response. Thanks Randy.

Another question. I just ran down to the local bearing supplier shop, and they did not have ceramics in stock, but would be happy to make them with a 1000 piece minimum order.

Anyone know where to get them?

PJ_TankPilot

Boca has them. Their web site is not easy to order from but it is do-able. Pay close attention to the letter codes so you don't get the wrong bearings.

The ceramics are not cheap but they should last a lot longer.

http://www.bocabearings.com

bl10

Dave:
I tried Boca Ceramic bearings in two Nelson Q40 engines a couple of years ago. I could tell absolutely no difference in performance. The ones I had used a nylon cage, which was easily damaged if overheated in the replacement process (I ruined both front bearings). I spoke to Pete Reed who spent his life working with bearings and he stated there is absolutely no performance advantage. The Boca Ceramic bearings were to a tighter clearance than the standard Nelson bearings and therefore the crank was much tighter when cold (wouldn't rock back and forth under its own weight). Seemed ok when hot. In theory Ceramic balls will last longer however the bearing will not withstand a crash any better than a standard one. The U-control crowd use ceramic balls a lot but they use custom fitted balls not Boca. They say the Boca Ceramic balls are not sized properly. My understanding is the cost of a custom fitted bearing is $5.00 per ball and you supply a new steel ball bearing. As for me my ceramic bearings are in a box somewhere and Nelson bearings are in my engines. I just change them if they feel at all rough and reseat them if the crank won't rock under its own weight.


Barry

daven

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Thanks for the reply Barry.

One more question. I purchased some bearings from a local bearing supplier (Gopher Bearing). The bearings I bought say "made in China" on them.

Are the bearings available from Dave Schadel of better quality, or should I be fine with what I purchased? The ones I bought were about $32 for the set.

PJ_TankPilot

I wouldn’t put bearings made in China in my TT 424 engines. A bearing that self-destructs can cause serious damage.

I don’t see how ceramic bearings could improve performance when bearings are new but after many hours, steel balls will have more wear and cause more RPM loss as the balls become non-spherical.

The Boca ‘High Performance’ steel ball bearings last longer than stock bearings in my TT engines. I am going to try a set of ceramics to see how long they last.

Replacing bearings is a minor pain in the neck so doing it less often may be worth the cost but I doubt it.

bl10

When purchasing bearings, especially for a high RPM engine like a Nelson or Jett, it is important to get them with the correct clearance. In the early days of ball bearing engines there was a lot of trouble with the bearings. When K&B and some others tried to use high quality high-grade bearings one of two things happened. If the outer race / case interference fit was tight enough to prevent the race from spinning when the case got hot the bearing would distort and bind the crank. If the crank would spin freely the bearing would eventually spin in the case. As I understand it Henry Nelson was the first one to use a "loose" (slightly smaller balls) bearing which would not distort with the interference fit into the case. In other words I would stick with Nelson bearings for Nelson, Jett for Jett and Boca for everything else. There are several grades of bearing which relate to clearance. Be sure you have the correct one. If the lower end is set-up correctly the crank should spin freely and should swing to the counter weight side when held and released. (rocking back and forth before stopping). I have had several cases where I've had to change cranks, blocks or bearings because I didn't like the lower end fit.


Barry

c/f

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I would atleast use a bearing with the lo friction composite ball retainers versus metal. Since I fly combat and use JETT 30's and have had a few bearing failures which destroy most the engine. Dubb to his credit has completely 100% backed up his product and I am a happy customer, I have also been enlightend into this subject matter along the way. One thing I found interesting is the crank to the inner race fit. On my Jett 30's the crank will spin freely in the inner race and not turn the balls. When I naturally assumed this was a manufacturing error, it was explained as a performance enhancement spec, since this is the fit that takes up the thermal expansion tolerance more effectively than ball sizing.
Atleast this is the way I understood it??

boater

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Just passing through and saw this thread. Most boaters have given up on ceramic bearings because after a little running they just seemed to be gritty, no amount of cleaning would remove the gritty feel. Cause unknown, most have gone back to Boca steel bearings with plastic retainer. Phenolic retainers seem to be porous and seem to hold nitro or water and will sometimes corrode or rust. Remember boat racers run 60% nitro and a tuned pipe, the pounding can be very hard on bearings (and conrods). The theory on ceramic bearings was the balls were lighter and were supposed to have less friction. Theory on not having your crank a press fit in the inner race is you want the pounding to not be on the same spot every rotation. The inner race being so small compared to the outer race gets the stress concertrated more. so there's some info for ya, its worth what you paid for it.