Trueseaker said:
Olivereaman said:
ShadowOSU said:
Running an aluminum sprocket should be no problem. We run them on 150 hp custom bikes that guys ride the crap out of (yes, they ride them as much as much as I do my Shadow), and they wear the same as any other sprocket.
The people making the sprockets out of aluminum do know what you are planning to use them for after all.
ShadowOSU,
I'd like to see a test, a real scientific test, conducted with the results showing that an aluminum sprocket will provide performance and longevity comparable to a steel sprocket before I'll believe it. I've been around sprockets and chains on Industrial, Construction and Farm machinery for many decades and I have to tell you, we haven't seen that happen yet.
As a practical test, just take a piece of steel and try to scratch a piece of aluminum, then take the aluminum and try to scratch the steel. What conclusion can be drawn from a test like that?
If people think they want aluminum sprockets, then they should go for them. But they should understand what they are getting.
Those people that make the aluminum sprockets do know what they're used for, and they are building them to make a profit. Have you ever seen any of them guarantee that they'll outlast steel?
That point shouldn't be lost.
John
There is one major difference between the scratch test you are suggesting and the use of aluminum as a rear sprocket: The sprocket is anodized. A good hard anodize is actually harder than cold-roll steel, what most sprockets are made out of. Now if you chip off the anodized layer, you're right the aluminum sprocket will wear much faster. I have made many medical tools out of aluminum (yes, 7075 t5 or t51 is best) and had them hard anodized. We made TONS of 1/2" 8-tooth gears that run at high RPMs for hours in surgery and they wear just fine.. they wouldn't need to be replaced after that work load except they are part of a disposable unit made mostly of plastic that is shot after one use.
Trueseaker,
Yes Trueseaker...you are 100% correct about anodizing. But anodizing, at least as I understand it is a two-edged sword. The anodizing itself is only a thousandth or two thick and very brittle. That's probably fine for a sterile operating room. But if you put it outside that sterile environment in a place where lubricants are trapping and holding abrasive particles that are being slashed and flung all over the place and using them like a sanding tool or a hammer, I wonder what happens when that first one thousandth wears away, or gets a nick in it. A steel gear is hardened to a depth well past a thousandth or two.
I know full well that there are great differences between hardness and ability to resist wear. Once the coating is gone, so's the hardness.
(I also thought, but not sure that the factor went to 6, but I may well be wrong about that too)
Believe me, I'm not trying to assault your post, but it seems like I see the same arguments all the time about aluminum and they use the same terms. I'm sure the gears are fine like you mentioned. And aluminum is a more suitable material if for no other reason than light weight.
I work with machines that have 800-1000 HP, cost between $650,00 and $850,000, and work continuously for thousands of hours in nothing short of hostile conditions, without rebuilding. I beleve these machines are engineered to be as trouble free as possible. I've never seen one....not one out of dozens of machines from different manufacturers use anything except steel. The sprockets themselves have weighed as much as probably 75 pounds. Aluminum could cut that number to a 1/3. I'm sure that cost is a factor in any machine but these machines put their value on durability, and they all use steel.
Even though I've been away from the business for awhile, I know that chainsaws used steel sprockets and there are few applications more demanding than that.
Augers for material movement that didn't dictate special conditions...again, never seen aluminum.
Aluminum is probably an exellent choice for things that are clean and don't impact much. But if you have either/both of those conditions.....I'm not an engineer and can't provide you with ASTM specs, just everyday experience, then I think steel is the material of choice.
We used to run race cars, they also used a bunch of lightweight materials. One thing to remeber it was that they had a crew of mechanics following it whenever it ran and they didn't really worry about what the cost of aluminum and titanium were. The budget for one car was something like $350,000/year and might have ran 40 hours/year. That's the difference between the race cars and the Asphalt Milling machines. They run at least 40 hours a week. The Milling Machines paid for the race cars, not the other way around.
Around here they do quite a bit of ATV racing and pulling. They measure their sprocket life in hours if they're running aluminum and years if they're running steel. The aluminum guys are the ones with deep pockets and the steel guys are usually paying their own way.
I'm still looking for that company that will guarantee that their aluminum sprockets will outwear steel. I think that was the main point of the discussion.
I'll even concede that there may be absolutely no reason to have such durabilty because on the technical side, the sprockets should be replaced at the same time as the chain, but again, that wasn't the point.
I enjoy these types of discussions because Ive been around long enough to know that things change all the time and I don't always, heck...hardly ever would be more like it, know about the new and different ways to do things.
John
