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M1combat
| | Posted on Friday, February 27, 2004 - 12:51 pm: | 
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Blake - I'm not going for the weight reduction as a means to increase top speed... More because I think it will make a better engine overall and I'll be in there anyway so I may as well. I'll be doing other stuff for more power that I'll then convert to more speed.
Jmartz - The Baker 6 fits a Buell XB? If so I'll be doing that just after the McBain treatment and before the other engine work. I HATE running down the road at >4000 RPM's...
Just to re-itterate... I'll not be doing this soon. I need to rebuild a 351C first but that shouldn't take too long... |
Blake
| | Posted on Friday, February 27, 2004 - 01:40 pm: |
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M1,
The "extra stuff" on the journal side is the flywheel. |
Jmartz
| | Posted on Friday, February 27, 2004 - 01:46 pm: |
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M1, my info above is a bit "dated". Since my semi-retirement from this forum, HD has made numerous changes like, 1.5 diameter press-in crank pins and no trans access except by engine splitting. I am afraid you are out of luck for a six speed on your XB. The 6th fit in the door that your engine does not have. You could adapt it if you were so inclined. Some milling, along with fat ugly welds and the baker cassette should do it just as long as you can resolve how to hold the back of the cases together. |
M1combat
| | Posted on Friday, February 27, 2004 - 02:32 pm: |
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Blake - Understood... I just don't see the point in having it unless it is used to start the engine like on a car. If that is the case, why not remove the inner portion to reduce weight (making it look something like a steering-wheel with the lower portion filled in). Only having just enough material on the journal side to preserve the flywheel strength so that it doesn't collapse due to the stress generated by the journal... Basically more like a V8 crankshaft with a "flywheel ring" built into it... Maybe I'm nutz, dumb or just plain uneducated... It could happen.
Jmartz - Damn, you got my hopes all up and stuff... I've wanted a Buell w/ 6-speed longer than I've had the Buell. As far as adaptation... It sounds interesting but I don't have a machine shop. Also, with the engine/transmission being a stressed member of the system I don't think I'd want to take it upon myself to modify any of that... Thanks for clarifying though. |
Benm2
| | Posted on Friday, February 27, 2004 - 03:27 pm: |
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Blake, roller bearings are sized according to L10 life, which is (loosely) the amount of time it will take for the bearing to fail at rated load, as you're probably aware. But, it will fail eventually. Maybe before the service life of the remainder of the components do, but it will. A properly lubricated journal bearing could last indefinitely. If we're being nitpicky, let's be clear.
Without leaving space for the rollers, the diameter of a plain-bearing journal could be larger than that of the existing crankpin, as the effective "roller" thickness is the oil film clearance. So, guessing, you could use 1.5" journal bearings to increase the load area and still be smaller than the rollers. Within the same OD parameters, the journal for a plain bearing COULD be much larger.
There's a whole chapter on plain bearing design in the engineering book on the desk behind me, but I can't design one now. Ducati's don't seem to have excessive offset between the cylinders, and that offset should match bearing width, per rod. Guessing at 3/4", that would put overall journal length around 1.5". I think its safe to assume that a ducati 998 motor produces nearly the same crankpin loads as the Buell.
Also, a plain-bearing crank could be made from one piece of steel. That would be much more rigid than the existing assembly. The trick would be to design plain-bearing rods that overlapped like the roller rods.
Here's a goofy idea. Replace the chain with a pair of spur gears, mounted up similarly to the aftermarket gear drives for 'merican v8's. Machine the gears to be counterweights, and set them up so their "tossing" inertia is 90 degrees opposite the cranks. With two gears, they could be phased at 180 degrees, so they'd only shake in, say, the horizontal plane. Viola, gear drive primary and vibration reduction.
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Fullpower
| | Posted on Friday, February 27, 2004 - 03:38 pm: |
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M1 nothin wrong with running 4000 rpm, thats right where the torque is. that little xb will run there happily all day, except for the frequent fuel stops. |
Blake
| | Posted on Friday, February 27, 2004 - 04:43 pm: |
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Ben,
"A properly lubricated journal bearing could last indefinitely."
So could a properly lubricated and understressed roller bearing. Is a crank journal always "properly lubricated", like say upon initial cranking of the engine?  I thought we already covered that, you even stated as much. So what are you trying to say, that in a perfect world where a journal bearing never loses lubrication pressure that it could operate forever? Yes, just as I stated above wrt deisel generator engines.
However, unless you fire up the oil pump before cranking your vehicle's engine, its journal bearings will see wear, and over time through many many such cranking cycles the journal bearings will eventually fail.
The larger diameter you use for a journal bearing, the less efficient that bearing will be.
I'm NOT arguing that rollers are better overall than journal bearings, just that a properly designed roller bearing is just as acceptable, just as viable, just as high tech, and in some ways superior to a journal bearing.
Are you sure that a contiguous crank is necessarily stiffer than a comparable bolted assembly? |
M1combat
| | Posted on Friday, February 27, 2004 - 06:13 pm: |
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"Are you sure that a contiguous crank is necessarily stiffer than a comparable bolted assembly?"
Well, I'm not comfortable saying that I'm "sure" about anything when it comes to engines  .
In your estimation, would the roller bearing stand up to the abuse I intend to put it through (~7.5K RPM's X 3-13/16 stroke (occasional track days where it would see this more frequently), ~125-130RWHP, daily driver duties, the occasional occurrence of bad fuel etc and be reliable?
If it will, would the crank be reliable knowing that if I DO use the roller bearing that it will need to be of the non-contiguous type AND have a smaller journal? I have heard that Ciccoto (SP?) shifts at 8500 on the Hals Buell. I figure that if I build it a lot like they have but turn it down at least 500-750 RPM's I should be alright... durability is an issue. Am I asking too much? |
Aesquire
| | Posted on Friday, February 27, 2004 - 08:13 pm: |
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The only setup I've read about for Sportster primary belt drives uses S&S cases, S&S crank w/bigtwin ends, & trapdoor setup to seal the oil in. Karata & Baker parts I believe. Closed primary no less.
Roller bearings biggest advantage is when oil pressure varies or is lost/not there. As in a 2 stroke. ( or big twin idling @ 600rpm) Plain bearings are fine, but can be more delicate / fussy, and can have more drag.
mototune article
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Benm2
| | Posted on Friday, February 27, 2004 - 09:24 pm: |
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In an underloaded bearing, the rollers may not turn, again leading to bearing failure. Also, as a roller bearing gets larger (to allow more load) it also gets larger, and gains more rotational mass to accelerate (the rollers, for instance, get accelerated a few different ways). So, likewise, it becomes less efficient.
Will it be reliable? If the bore goes from 3.5" to 3 13/16", the area goes from 9.62 sq inches to 11.4 sq inches. At 1000psi combustion pressure, the bearing load goes from 9600 lb to 11,400 lb. Stronger rods will help transmit the load to the bearings, but they will have to handle the loads. Reliability will go down.
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Benm2
| | Posted on Friday, February 27, 2004 - 09:31 pm: |
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Blake:
Yes, a one-piece crank of the same material construction, diameters, journal sizes, etc. will be stiffer. If you assembled a multi-piece crank from press or taper fits, there will always be sliding surfaces available for very high stresses. And, assembly with very tight press fits will just fill the assembly with residual stresses.
Roller bearings have many applications, and serve very well in them. They are, as you suggest, superior in many ways, especially if you can't produce an oil flow for a journal bearing. Also, preloaded roller bearings can produce rotating assemblies that have no slop in them. |
Mikej
| | Posted on Monday, March 01, 2004 - 09:14 am: |
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"Here's a goofy idea. Replace the chain with a pair of spur gears,"
I've seen some pictures of a bike with this done. I don't recall the net effect nor longevity nor effort involved to do so. Was back when I knew a family with an independant shop who's kids raced H-D's on the flat track circuit. That was many many moons ago. |
Blake
| | Posted on Monday, March 01, 2004 - 02:47 pm: |
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Ben,
How would residual stresses affect stiffness? I tend to agree that a billet piece would be stiffer, but how much more so is the question in my mind. It seems to me that if done right and preloaded and press fit, the multi-piece assembly could get pretty darn near the stiffness of the billet piece. For example, an single length of all-thread tension rod may be no stiffer than two half-length pieces joined by a threaded collar. A larger crank journal would certainly stiffen up the whole assembly. There is a LOT of stress going on in that little part. |
Benm2
| | Posted on Monday, March 01, 2004 - 09:28 pm: |
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The residual stresses would affect life, not stiffness. I only mentioned it in reference to certain types of interference fits (like heating one part, or chilling another before forced assembly). Those types of assembly would reduce the possibility that additional loads would cause slippage, which is where I thought you might be headed.
Mike, was the gear drive just for transmission, or did it have counterweights for vibration reduction? Probably tough to tell from a picture, but its interesting to hear that it's been done before. I'd sure like to discuss it with the "inventor", THAT would be an interesting conversation. |
Blake
| | Posted on Monday, March 01, 2004 - 10:45 pm: |
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Gears change the loading of the cases and crank bearings. Instead of the load acting on the sprocket in the direction of the chain at roughly tangential to the 12 0'clock position, it would act downwards roughly tangential to the 4 o'clock position. That could be good or bad or of no significant cansequence. I would think however that such an arrangement would increase the design loads for the crank bearings; more direct/parallel addition of the piston-rod and drive gear loads upon the crank bearings (both loads acting downwards where before the chain was pulling rearwards on the sprocket). Please don't make me draw a picture. ![: ]](http://www.badweatherbikers.com/buell/clipart/proud.gif) |
Mikej
| | Posted on Tuesday, March 02, 2004 - 08:37 am: |
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Ben,
It was a long time ago and I don't know the details, just the general photo semi-public stuff about it. Sorry. As I understood it the setup was basically to do away with the primary chain setup in a semi-XL type of engine case. |
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