Needle bearing con rods or Bushed con rods

[Scott Schneider]

Bushed connecting rods have been the standard for years now in our nitro engines and have proven themselfs to be quite durable and reliable.

If they do fail most times they spin first in the rod then overheat and distroy the rod.

Needles are for the most part only able to run in a steel rod thats heavy relitive to aluminum but are real tough !! Are we sacrificing performance for reliablity?

With our engines and application is a needle rod really better?

Needles can run in a much lower lubricant enviroment than a bushing can, but ALL the MFG. still want us to run a 20% oil content. SO WHAT GIVES ??

:unsure: Scott

 

[Don Ferrette]

"Needles can run in a much lower lubricant enviroment than a bushing can, but ALL the MFG. still want us to run a 20% oil content. SO WHAT GIVES ??"

Very true, IF one can behave with the needle settings. But THAT's the problem, too many can't & wind up frying the motors since you have less oil in there to start with. <_<

 

[jasoncsc]

I am still a newbie, but....

Personally, my first engine that run rollers on the conrod is the CMB 45 Evo 2/2, and in less than 10 tanks its been through 3 sets of con-rods, rollers and crankpins, one set ruin right after a change and before launch....Gladly some local gurus told me its not my fault in breaking these rods.... <_<

I next tried Picco with a bushed corod and have no problems whatsoever....

Don just sold me two of his Mac 45 and I hope it would revert my fears for conrods that runs on rollers

My 0.0002 cents...

 

[Ian Inverarity]

The needle roller rods are more tolerant of leans runs. These can happen for reasons other than simple setting the needle wrong, like tank problems, tears in the fuel lines etc, and in a bushed rod engine that can be the end of it.

Probably the lighter alloy rods do allow higher performance, but I prefer an engine that is tolerant of mixture problems and more durable, and I guess the popularity of engines like CMB's and MAC's means that a lot of other boaters do too!

Ian.

 

[Don Ferrette]

" The needle roller rods are more tolerant of leans runs. These can happen for reasons other than simple setting the needle wrong, like tank problems, tears in the fuel lines etc, and in a bushed rod engine that can be the end of it."

On this I will definitely agree when you are talking about equal oil content in both motors. I personally prefer the needle set up. However, where you see the problem is guys starting out with a significantly lower oil content because they've heard the motors don't need the same amount of oil. Then getting too tight on the needle settings. I run 15% oil on my motors & it works great but I also don't get crazy with the remote needle either....

 

[AndyBrown]

Of all the MAC engines that have been put into service only ONE has had the needles go out. If there were two I don't know about the second one.

Not all Steel needle bearing rod engines are created equal as some do have problems with the needle/rod assemblies if you run them too lean.

Jason, The MAC 45's have never had a problem with rod needles, so be reassured.

 

[Don Ferrette]

Also the MAC needles get excellent lubrication just by the drum design itself. With the fuel/oil mixture leaving the back of the drum it's constantly dumping on the needles!

I actually modify the drums on the CMB cam series motors with an oiling hole to feed lubrication to the needles which I consider a must do on the 67's & 80's-