Roller bearing crankshaft

[turboblue]

[OGSquare]

[junior55]

I saw a segmented "bolt together" & "SPLINED" coupled full-circle-roller crank somewhere around on the web and it still had a list of problems that made it impractical in real life conditions.

[EZGZ]

I have a SPG flywheel that was made for the roller crank.
It is aluminum and weighs about 7lbs. It has the steel starter ring and a steel peace for the clutch to ride against.

When I tried it on my standard crank 1776 it worked ok. Reved faster due to the weight savings but had a unusual sound when starting. would kind of ring like a bell.......

Anyway, I guess the lighter weight flywheel was to offset the heavy crank.

I always heard that they ran nice a smooth and helped low end power. Guess they weren't ment for sustained high RPM though.

Cool idea. Has worked great on the Harley Davidson V-twins for many decades.
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64 custom Ghia, 66 Bug, Sandrail, Barrien tub

[turboblue]

[Stuggi]

I've read somewhere that they didn't reduce friction that much, and the roller cranks still use normal case bearings in VW applications, it's just the rod-bearings that are different, at least on the ones I've seen.

And it's like putting an unexploded WWII hand-grenade in your engine, if it gets jerked out of index it'll destroy your engine in a very effective fashion.
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1970 Beetle
1969 Panelvan

Orange VW Fest!
Pulled out of a Lake Fest!

[sbnova]

[ALB]

They reduce friction considerably- enough to make a stock cammed motor with dual carbs run like the same plain crank motor with a 280 degree cam (see my previous post). Iirc the main bearings had to be modified so the big ends of the rods were lubed with a constant spray or mist of oil. Al

[Jengel451]

[special-k]

Actually roller bearing get away with a lot less oil supply. Thats why 2 strokes and modern 4 stroke dirt bikes use them. Kawasaki used them for years on H-1's and Z-1's and they were the bike to have for drag racing for more than 20 years. The only reason car/bike companies went to plain bearings was to save money initially. My .02 cents.

[perrib]

If your on a budget a roller crank is not for you. A roller engine is a blast to drive offroad. I got to use my friends Baja with 2180 roller engine. The engine had a lot of hard miles on it. He had run many off road stadium races with it. He did state it was very expensive to make them work. You would be better off using a plain bearing crank.

[tncsparky]

look what i have

82mm empi roller that is pinned

[fiftysevenvw]

After looking at the pics. the rod side clearance looks awful excessive. Is that normal for a roller crank? The oil must gush out quite fast and how do you keep the oil pressure at an acceptable range? There is a lot of dirt on that crank and cleaning it, how can you be sure the dirt isn't accumulated in the rod bearing area? Just something to consider.

[gears]

There isn't any oil pressure to lose from the rod bearings. Oil is sprayed to the rod externally from notched main bearings (which is why the rod's large side clearance and windows are important design features).

Yes, oil cleanliness is critical with the SPG.

I've seen the earliest (non-pinned) 82mm stroker SPG last 20 years in a high performance street engine. They weren't intended for drag racing.

[Terry Cloyd]

Too funny that the Inch Pincher drag raced with a roller crank. It had 88mm bore x 82mm stroke with SPG roller crank assembly and dual 48IDA Webers, EMPI 851 camshaft and 39mm x 35.5mm ported heads. All you need to do is to pin the cranks in 4 places to keep them from twisting out of index.

[Vanapplebomb]

Some of you guys might find this cool. Tatra uses roller bearings on their disk web crankshafts. They are bolted together subassemblies so they can put all the rollers on. The main bearings on their v8 and v12 diesel engines are massive! These diesels are built to the hilt, no cost object engines.

Notice the 7 large main bearings on the crank webs. This is the crankshaft used in Tatras v12 diesel engines.

This is what a v8 Tatra engine look like from the outside. It is just over 12 liters and is fully air cooled. What a beast!

This is one of the massive trucks that the engines are installed in.

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1800 Type 4 Berrien 295

http://www.thesamba.com/vw/forum/viewtopic.php?t=487021

[vdubwizard]

If anyone has any questions about the roller crank, as in a fix, repairs, or pinning, the newest found Roller Guru is "Gary, The Roller Crank Guru at 714-997-9785 " as of 2012 when I called him, he is in or near Anaheim, CA.
Plan on calling him myself soon for a couple roller cranks. Pinning, indexing, and rod pin bushing all is simple tasks for Gary, hope to send him a crank soon for a long term engine ( street, not drags). Don't drop the clutch! G
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Please use <vdubwizard> for all messages, Big foot does not work correctly? Long rod Engines slow the piston down at TDC and BDC to let more flow and less angle to the pistons which helps the engine to last longer, less wear, and move the power band up the scale a bit.

[Quokka42]

Roller bearings definitely have a friction advantage when pressurised oil to the bearing isn't available, but the factor that hasn't been brought up this time around is their behaviour under detonation - they can quickly become toast!
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There has only ever been one man who was perfect, and they nailed Him to a cross.

[Bashr52]

Roller cranks are cool, but in a 1641? Why bother?

[raygreenwood]

Uh....no....roller bearing, cranks have no friction reduction properties. There is many, many studies done all the way back to the advent of roller bearings being used in the first steam locomotives (Timkin project). In that individual case because journal box bearings had much higher rolling resistance.

Roller bearing cranks were found by aircraft companies, motorcyle manufacturers and a wide range of others...to have lower rolling resistance and less wear to the very expensive crank.

But because of more metal to metal contact, within the bearing itself....the roller bearing actually has more friction, heat and a shorter life.

For the most part, only low budget (and thats a relative term) auto crank mfgs and motorcycle engine mfgs whose cranks and engines are much lower rotating mass.....made pressed together roller cranks.

Most high end applications were either splined or pinned journals.

Friction and rolling resistance are joined at the hip but are NOT the same thing. The only use for roller cranks was reduction of rolling resistance making for a more free revving engine. This made for noticeable inefficiencies in engines when maintaining engine rpm at high speeds when right on the fringe of adding power or technically coasting.

This was the original efficiency use in steam locomotives. Once up to speed there was a definite reduction in coal usage in tons per 100 miles in sustaining, speed. Ray