Roller crank vs. shell bearings..

[Anonymous]

Hey brit7.11, it looks like you like plain bearing cranks as much as I like rollers....... Hope you will be as lucky with your plains as I've been with my rollers

I wish you'd read my posts properly. I have already said that I like rollers, and my only point is that ........ oh I'm fed up typing it. Please read through my previous posts and try to take in what I'm saying.

And BTW, I don't have any bikes with plain bearing cranks. I've got a GS1000S and a GS750 with a 1085cc tuned engine. I love roller bearing cranks!! They're extremely tolerant of age and less-than-perfect maintenance, but my point is purely about strength, and I've tried to illustrate this.

[Hap Call]

My question has more to do with nomenclature...what are Cobblers?

Hap

[redliner1973]

Sorry Tim, but that doesn't make sense.

Is price really an issue in a Formula One car, or a Moto GP bike? I hardly think so. And I already said that yes, one piece cranks are cheaper to produce, but that doesn't mean they are worse, does it? After all, who recently had a crank wear out in their plain bearing car?

And turbine engines are a completely different kettle of fish to reciprocating engines. The requirements for the bearings for a gas turbine are totally different. For instance, radial loadings are quite low, but axial loadings can be quite high. You can't compare a bearing in a turbine to a bearing in a piston engine. Faster isn't necessarily better!

There have been tests done on plain bearing crank bikes in this country. A Honda CBR600 with 160,000 miles on the clock was stripped and found to have negligible wear. Would a roller bearing crank have lasted longer? Very possibly, but who cares? The point is that given proper care, a plain bearing crank will last as long as the rest of the bike.

Don't get me wrong, I like roller bearing cranks, but I think that to say that plain bearing cranks won't take the load isn't true. There are plenty of highly tuned GSXR's (and all sorts of cars etc.) out there to prove different.

You have to keep in mind that the Formula one car's engine is tore down after every race, so it really would not matter which bearing was used, except that a roller would be more expensive than a plain....and when your a sponser that craps out 500k+ per engine with plains, and close to $1Mil with rollers, do the math..hmmmm, one race...tore down...both can rev to 16k...$500k vs 1 mil.... one race...you get my point there. As for the turbine engine, yes, radial loads are light, seems a PERFECT environment for a bearing which relies in a film of oil to maintain clearance.
As for a plain crank not wearing much? most automotive engine i see have to have the cranks turned down at EVERY rebuild, whislt a roller usually can be inspected and reused without anything done to it. This is the reasons i am saying that a plain is used for cost-efficiency Vs a roller. Look at how many old GS's are running around today. Do you really think there will be alot of these new 15000RPM plus plain bearing superbikes running around 20 years from now WITHOUT having had an overhaul?? I still believe a roller outdoes a plain anytime...JMHO in good spirits!! :twisted:

[Anonymous]

My question has more to do with nomenclature...what are Cobblers?

Hap

Either a.) A person who repairs footwear or
b.) Bollocks, or cohones to you.

[Hap Call]

My question has more to do with nomenclature...what are Cobblers?

Hap

Either a.) A person who repairs footwear or
b.) Bollocks, or cohones to you.

Hap

[Anonymous]

Come on propflux man, you've quoted me but ignored just about everything I wrote!

and when your a sponser that craps out 500k+ per engine with plains, and close to $1Mil with rollers, do the math..hmmmm, one race...tore down...both can rev to 16k...$500k vs 1 mil.... one race...you get my point there

There's no way a roller bearing crank costs twice what a plain bearing does!!

As for the turbine engine, yes, radial loads are light, seems a PERFECT environment for a bearing which relies in a film of oil to maintain clearance.

There are other factors, as I implied, which dictate the choice of bearing in gas turbine engines. Roller bearings are NOT chosen in this application for their "strength". ( Note I mean ability to take load )

As for a plain crank not wearing much? most automotive engine i see have to have the cranks turned down at EVERY rebuild,

In this country, almost no car engines are rebuilt before the vehicle is scrapped. By far the vast majority of plain bearing cranks will outlast the rest of the vehicle given adequate maintenance. As I said (if you would just READ my posts) and I quote myself:"Would a roller bearing crank have lasted longer? Very possibly, but who cares? The point is that given proper care, a plain bearing crank will last as long as the rest of the bike. "


This is the reasons i am saying that a plain is used for cost-efficiency Vs a roller.

The very first thing I wrote in this thread was: "Main reasons would be manufacturing based, i.e. that plain bearing cranks are cheaper to make and are probably quieter and therefore more easily fit into recent noise regs"

Do you really think there will be alot of these new 15000RPM plus plain bearing superbikes running around 20 years from now WITHOUT having had an overhaul??

No of course I don't!!! I've already said as much. A roller will always last longer, all other things being equal. But the original question was about strength, not decades of durability! I have already mentioned Kent Stotz's championship winning 500bhp Honda Blackbird , and there are literally hundreds of blown Busa's in cars and bikes out there, some with nitrous, proving the strength issue. Very long term durability? Rollers every time.

One last point: I am rebuilding currently a GS1150 motor for a customer. I have just taken the (roller) crank to my crank specialist to be rebuilt. Why? Because the #1 big end had gone.

[cbxchris]

brit there is a complete set of 1150 rods on ebay now for a 100 bucks...they are new

[Don Lobacz]

Brit, well said. The Kawasaki problem is the only one I can think of, and that may well be aggravated by the abuse that bikes get over here: bikes are often subjected to gas-diluted oil, 3-year-in-the-bike oil, and now extended-wheelie lack of oil. Plain bearings are much more than just adequate, otherwise the manufacturers would not put them in their technical marvels. At the extreme edge of use, rollers will do better. This thread started because someone wondered if it was simply an A vs B choice, and if B costs $100 more then we would gladly pay it. The problem is that for the manufacturers, that $100 has to be multiplied by hundreds of thousands of units which equals tens of millions of dollars. Demand for rollers has not yet overcome that kind of financial inertia.

[Anonymous]

I believe that Mr. Suzuki chose rollers because he was in that business.

[Anonymous]

Thanks for the tip Chris, but by the time I got them over here with shipping and import duty, they'd be twice that! Hopefully I only need one rod anyway.

Thanks for the kind words Don. Kawa's have alwyas been known to be weaker over here, with problems with cranks, valve seats, head wear etc. Honda's on the other hand have a rep for being bulletproof, with bikes like the CX500 and NTV650 (plain bearing cranks) racking up huge mileages in the hands of despatch riders. (do you have those?) I'm talking 200,000 miles plus in some cases, with no strip downs and only adequate maintenance.

[redliner1973]

Brit, maybe I was wrong, But I though strength = Durability.... :twisted:

[Anonymous]

Well, in engineering terms no. Strength in engineering terms, as far as I understand it, relates to a material or components ability to resist loads.

Therefore a "strong" crank will resist 400bhp, whereas the "weaker" one will break at 300bhp. However if both cranks are only subjected to 200bhp, the "weaker " one may well last twice as long and would therefore be more durable.

I know that in the US, the word durable is used a lot more than it is over here, and it has suffered from definition creep!

Britain and America. Two nations divided by a common language.

[earlfor]

Its a pie with the crust on the top instead of the bottom. They usually come in apple, peach, blueberry, cherry, etc. :-) :-) :-) :-)

Earl

My question has more to do with nomenclature...what are Cobblers?

Hap

[Mark Harrop]

revolution

Lots of good info...just like I've come to expect from this site. I feel G'd up on cranks now. (G'd up is hip hop slang my kids use, means informed)

But when I read this...
"Cobblers!"

I had to spit my drink back in the glass.

Thanks for the info guys. But why is there no selection of bearing shells for my GS or gixxer 750?

[redliner1973]

Re: revolution

.

Thanks for the info guys. But why is there no selection of bearing shells for my GS or gixxer 750?

Thats because so many wore out so quick they cannot keep up with demand....(sorry, I just couldn't resist!) :twisted: