Piston weights
- Thread starter madass140
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First let me say that I heard that your neck of the woods was under typhoon attack, I hope that the damage is nothing like the last disaster, do let us know.
RE: Piston weights. Piston weights vary widely, depending on who makes them. Pistons even vary in pairs, enough that judicious balancing will end up shaving a bit of skirt to make the match. There is much to say about quality, but then it depends on what you expect your engine to do for you. Some sources like the Emglo, some need OE Hepolites (where they can be found). Specialty manufactures will make you any shape size for a price; I found that it was less expensive to purchase a pair of Arias forged pistons for my BMW R90S than to purchase OE BMW slugs ($450 vs $900---for the pair).
But.
Piston weight isn't so much the issue as how far you are willing to go to balance your rotating/reciprocating parts. You get a good balancing service and it almost doesn't matter what the piston weights are because they become part of a matched assembly. Purchase a good quality set of pistons, get parts balanced and make sure that you have the right piston/bore clearance and go worry about something else...
Bill.
RE: Piston weights. Piston weights vary widely, depending on who makes them. Pistons even vary in pairs, enough that judicious balancing will end up shaving a bit of skirt to make the match. There is much to say about quality, but then it depends on what you expect your engine to do for you. Some sources like the Emglo, some need OE Hepolites (where they can be found). Specialty manufactures will make you any shape size for a price; I found that it was less expensive to purchase a pair of Arias forged pistons for my BMW R90S than to purchase OE BMW slugs ($450 vs $900---for the pair).
But.
Piston weight isn't so much the issue as how far you are willing to go to balance your rotating/reciprocating parts. You get a good balancing service and it almost doesn't matter what the piston weights are because they become part of a matched assembly. Purchase a good quality set of pistons, get parts balanced and make sure that you have the right piston/bore clearance and go worry about something else...
Bill.
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'Piston weight isn't so much the issue as how far you are willing to go to balance your rotating/reciprocating parts. You get a good balancing service and it almost doesn't matter what the piston weights are because they become part of a matched assembly. Purchase a good quality set of pistons, get parts balanced and make sure that you have the right piston/bore clearance and go worry about something else...'
Doesn't it take energy to accelerate and decelerate the pistons at the top and bottom of the stroke ? And isn't the force on the rod a squared relationship of the piston mass times the acceleration ? Surely lighter pistons in a motor give better performance and less likelihood of stretching a rod when the motor is revving hard ?
Doesn't it take energy to accelerate and decelerate the pistons at the top and bottom of the stroke ? And isn't the force on the rod a squared relationship of the piston mass times the acceleration ? Surely lighter pistons in a motor give better performance and less likelihood of stretching a rod when the motor is revving hard ?
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Doesn't it take energy to accelerate and decelerate the pistons at the top and bottom of the stroke ? And isn't the force on the rod a squared relationship of the piston mass times the acceleration ? Surely lighter pistons in a motor give better performance and less likelihood of stretching a rod when the motor is revving hard ?
Sure.
As I mentioned earlier: Match the piston with your intended use of the engine: Want to go racing? lighter is better. Want to enjoy the countryside? Piston weight isn't a factor.
Sure.
As I mentioned earlier: Match the piston with your intended use of the engine: Want to go racing? lighter is better. Want to enjoy the countryside? Piston weight isn't a factor.
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There are plenty of street Commandos with cracked cranks or cases. I've had them come in for balancing and found them to be cracked. It depends how much time is on them and whether they've been babied or not. If its a cafe bike (and Nortons make great cafe bikes) then they are at risk and the heavier the pistons are, the worse its going to shake no matter how well you have it balanced because its always going to be out of balance somewhere in its rotation depending on the location of the crank journal throughout its revolution. The heavier the pistons - the worse those out of balance areas are going to be. Nortons shake bad enough to need isolastics. They don't smooth out until you get the pistons down in the low 200 gram range (the lighter the better). That will never happen with stock type Norton pistons because the pin is not located close to the rings - its located further down and when a pistons is designed that way it needs webbing or other bracing to reinforce the distance between the pin and the rings - that extra reinforcing adds a lot of weight and makes for a longer heavier piston. Modern pistons designs have addressed this problem and are much lighter. They have to be. Otherwise todays high revving motors would explode.
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madass140 said:
Unfortunately there's not enough weight difference (as in reduction) between brands with the stock type piston design to really help. But you will find that some pistons - especially those based on car piston blanks - are even heavier.
Your Avitar looks like a featherbed style with a modern Triumph motor using counterbalancers. Those are smooth motors.
Rohan said:
Titanium is not a suitable material, it has really bad wear characteristics, galling and micro welding.... It will weld itself to your piston rings and tear apart your bore at the same time. Im not sure that you would actually be much better off in terms of mas either
Cheesy said:
Ti is lighter than aluminium (alloys), considerably.
And much stronger too.
So pistons could be minimal metal for much reduced weight.
Perhaps coatings could reduce the wear /unsuitability factor ?
P.S. Ti pistons are rumoured to be in F1 cars ??
May explain the 20+ coatings said to be involved in F1 piston technology.
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Not at 'puter with piston wt's numbers but hi end lightened Costworth pistons and Norton rod's Peel 920 was balanced to normal > shot up to 90's BF with JSM kit > to give some prespective of sticking with regualr piston designs mass range no matter the exotic current market alloys. Next era almost for sale is hybrid glass/ceramic/nano powered metal units fused in metameterial biological units grown more than forged or machined in shapes that self correct with thremal flows and allow for internal hollows and bracing for even less mass plus coolant paths. Before that a re think of linear to rotary motion gizmos might work with todays off the shelf allows and machining. But then would spin so fast and free would need a crank and peddle OHC drive to keep its Commando cute profile.
lcrken
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Rohan said:
Yes, someone has made pistons out of titanium. The ex-Boeing design engineer I hired to design titanium Commando rods some years back (a titanium design specialist who took my $ and then went bankrupt), showed me one of a set of titanium pistons that had been run in a NASCAR engine. It was an interesting design, with a hydroformed body, and bearing caps for the pin that looked like small rod bearing caps, and bolted to the underside of the dome. I've forgotten what the coating was on the skirt, but it was coated. The engineer said it worked well, but I have no other info on it.
There have been a lot of different materials tried for pistons over the years, but aluminum does seem to be the material of choice for car and bike IC engines. I recall a research project at least a couple decades ago that tried a two piece piston, with an aluminum top and plastic (Torlon, I think) skirt. Plenty of cast iron and steel pistons around for large industrial and marine diesels as well. I've also seen an SAE paper or two on a two piece ceramic top/aluminum skirt experimental piston. There have even been attempts to use magnesium alloys for pistons (Porsche, I think), but they don't appear to have been too successful. I'm sure there have been plenty of other materials tried. Some of the aluminum/carbide MMC alloys look like they would make good pistons, but the machining is considerably more expensive than for conventional alloys. Still, there's always new materials to try.
Ken
Err yes, engage brain before writing.
Its the thin sections still with good strength that makes Ti possible to be lightweight designs, and like Allan says.
Its magnesium that is much lighter than aluminium = density.
Thanks Ken.
We notice that hi-speed drills have some sort of Titanium coating,
and also the working surface of some of these upsidedown forks.
If your man went bankrupt, perhaps there is a moral there = maybe to be wary of Ti pistons ?!?
I recall that Lynite was a popular material in the 1920s in the USA. Including for pistons. ??
Its a magnesium aluminium alloy ?
I have a sump cast in it, although not sure how much Mg is in it.....
Its the thin sections still with good strength that makes Ti possible to be lightweight designs, and like Allan says.
Its magnesium that is much lighter than aluminium = density.
Thanks Ken.
We notice that hi-speed drills have some sort of Titanium coating,
and also the working surface of some of these upsidedown forks.
If your man went bankrupt, perhaps there is a moral there = maybe to be wary of Ti pistons ?!?
I recall that Lynite was a popular material in the 1920s in the USA. Including for pistons. ??
Its a magnesium aluminium alloy ?
I have a sump cast in it, although not sure how much Mg is in it.....
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New steel piston technology that may not apply to cast iron cylinder
http://www.greencarcongress.com/2014/08 ... steel.html
http://www.greencarcongress.com/2014/06 ... nault.html
For the non diesel Nortons to come...
http://www.screamandfly.com/showthread. ... n-Material
http://www.greencarcongress.com/2014/08 ... steel.html
http://www.greencarcongress.com/2014/06 ... nault.html
For the non diesel Nortons to come...
http://www.screamandfly.com/showthread. ... n-Material
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