Standard crank with roller bearings

[Andrej]

While perusing the innards of a scrapped engine casing (bad line boring job), I pondered installing roller or needle bearings on the standard crankshaft main journals no's 1; 3 & 4. Anyone know if this has been done before?

[Bugger]

Hi The older days one used to get Roller bearing cranks but only on the rod jurnals as My knowlege tell me
The metalurgy of bearings has grown the last couple of years so no really need of Rollerbearings for a crank
There are more contact surface at any given time as to White metal bearings between the crank and casing and you need more oil flow and preassure to keep things happy

On the Beetle transmissions for racing we sometimes use HAND PACKED needle bearings but these boxes is for no street use good as the bearings have alot of friction against oneanother
But for drag racing that is over quick the shafts have very little place to move to and makes internals stay together better
so I would say shelf that

[Andrej]

Thanks Bugger, I found the following in Bill Fisher's "How to HOTROD VW ENGINES" concerning roller bearing cranks which as jou correctly point out only have roller bearings on the conrod journals.

"Ted Trevor of Crown Manufacturing measured the frictional differences between a roller bearing and a pressure lubricated plain bearing. The tests showed that the pressure-lubed plain bearing had less friction than the roller bearing".

I am surprised, but at this point I agree with you to shelve the idea and scrap the case, maybe set it on fire and see if it really does burn.

[fig]

I am surprised, but at this point I agree with you to shelve the idea and scrap the case, maybe set it on fire and see if it really does burn.

Join us at the next Kaapse Kombi Kult kamp-out for our annual case burn. They do indeed burn very brightly.

The other downside of roller cranks is they are very sensitive to detonation and will develop flat spots on the crank journals as a result, which turns them to instant scrap.

[Tony Z]

and with a heavy launch they can twist and put pistons through heads

[IMPI]

The biggest hassle with rollers is that you need pretty fancy oils with a high zinc content to make them live. modern oils have very little zinc as it clogs the catalytic converters (some bike oils are better in this regard as the sump and gearbox share the same casing. This also applies to flat tappet engines (ours)
Armand

[RICKY-R69]

Roller bearing were used sucessfully in dkw engines on mains and big ends but then again,it was two stroke engines