Reciprocating mass

[B0000M]

yeah wow interesting stuff. Got that one wrong lol. so what has more effect on handling would be interesting to know... recipricating mass off piston/conrod/valve train or the spinning flywheel weight? and what do we call the spinning flywheel weight 'cos it ain't unsprung weight....?

flywheel is just rotating mass, which is sprung weight, as its attached to the main section of the bike

[bogan]

yeah wow interesting stuff. Got that one wrong lol. so what has more effect on handling would be interesting to know... recipricating mass off piston/conrod/valve train or the spinning flywheel weight? and what do we call the spinning flywheel weight 'cos it ain't unsprung weight....?

i would say the flywheel has more effect on handling as the rotational inertia stored in it makes it more difficult to change direction. But the effect would probably be largely overshadowed by the same effect generated by the wheels.

[CookMySock]

recipricating mass off piston/conrod/valve train or the spinning flywheel weight? and what do we call the spinning flywheel weight 'cos it ain't unsprung weight....?

In the engine? Thats just part of the sprung weight of the bike. That it's rotating is not relevant to the suspension.

In the wheel? Thats part of the suspensions reciprocating mass. It's not reciprocating coz its going round and round, it's reciprocating coz its going up and down as part of the suspension. The round and round bit here is not relevant, EXCEPT that the more mass there is in the outer parts of the wheel - the stiffer the steering will be as the wheel acts as a gyroscope.

I think.

Steve

[NDORFN]

To answer your question properly as requested, I have no idea what reciprocating mass is and could only speculate based on the wording that it has something to do with a mass that reciprocates.

[Buddy L]

I had my rotating mass mixed up with my reciprocating mass, but understand alot better now.
The advantages of going to school up north and having limited options.

[BMWST?]

yeah wow interesting stuff. Got that one wrong lol. so what has more effect on handling would be interesting to know... recipricating mass off piston/conrod/valve train or the spinning flywheel weight? and what do we call the spinning flywheel weight 'cos it ain't unsprung weight....?

the spinning flywheel would have a gyroscopic effect,and a tourque reaction(think about teh bmw inline flat twins n fours)

[cheese]

i would say the flywheel has more effect on handling as the rotational inertia stored in it makes it more difficult to change direction. But the effect would probably be largely overshadowed by the same effect generated by the wheels.

Would this be the the gyro effect? I recall seeing recently on discovery channel a bit about some guys trying to build the next bike super road bike. I think (from memory) that they made a 4 cylinder engine (north south) with two pistons spinning one way and two in the opposite direction and then coupled through a set of gears much like a differential (not sure I explained that well or right). Anyway the end result was a bike with very little "gyro effect" (I'm still not sure that is the correct term). The tester that they got to test the bike said that cornering with it was amazing, a normal bike you have to push it hard to lean over and this one would glide around with ease.

[xwhatsit]

Flywheel effect? Well, why do you need a dab of right rudder on your DH.82 when the tail lifts off the ground?

[Reckless]

I've given this one a bit of thought these last few years after my experiments with the XT400/500/600/621.The changes in an identical bike with changes in reciprocating mass were very marked....it's not so much an engine capacity difference,it's the reciprocating mass.The 400cc engine,with shorter stroke,lighter flywheel etc was much easier to ride - just flicked through the gears up and down without any effect on the motorcycle itself.Just riding the bigger capacity engine bike,it felt heavier,you could really feel the capacity change through the reciprocating mass.The bigger capacity bike was much more powerful of course,but harder to ride.Coming out of turns there was heaps of wheelspin of course....but more than could be controlled by just the throttle.Most noticeable was coming into turns - the smaller capacity bike was very stable,I was able to set up slides with ease....the bigger engines were almost uncontrollable by contrast.I could just rail the turns on the little engine,and was a total mess with the bigger engine.

So when I wanted a BMW airhead to set up for gravel roads - I went for the small capacity R65.Less reciprocating mass means less wheel spin out of turns,and is much more stable on turn entry.The road surface is able to control engine speed....rather than the engine dictate things.

Also after the DT230,I found lack of engine braking a big advantage....2 strokes have that advantage.MotoGP teams have spent as much effort reducing engine braking as gaining HP.

Dunno if this is what you want to hear - but I want minimal engine braking,and an engine that can react to surface conditions to maintain traction.I'm all for less reciprocating mass.

Which is why some of us ride ride 200cc 2 smokers instead of those big 450"s LOL!!!

I think we will hear more of this rotating mass theory as time goes on. Bikes are revving very much higher and their will be more investigation into the effects of the engine (well 4 strokes anyway) on the dynamics of bikes (road and off road) bearing in mind engines are now part of the chassis not just rubber mounted and sitting in it anymore.

The latest Husaberg is testing these principles with its new engine layout here is what is being said about it:
That high price does get you a radical motorcycle. The new 70-degree engine configuration (denoting the slope of the nearly horizontal cylinder) is no gimmick. Practically flipping an ordinary layout, the design positions the crankshaft very close to the bike's overall center of gravity. This puts the engine's largest rotating component at a neutral location in the chassis, result being that the big four-stroke motor's mass is less noticeable to the rider.

Like holding a skill saw out while its going and then turning it. You can feel the rotational effects of the spinning blade and motor on the balance of the saw as you turn it over!

Interesting stuff!! I wonder if Ktm will adopt the Husaburg theories for their mainstream bikes???

[bogan]

Would this be the the gyro effect? I recall seeing recently on discovery channel a bit about some guys trying to build the next bike super road bike. I think (from memory) that they made a 4 cylinder engine (north south) with two pistons spinning one way and two in the opposite direction and then coupled through a set of gears much like a differential (not sure I explained that well or right). Anyway the end result was a bike with very little "gyro effect" (I'm still not sure that is the correct term). The tester that they got to test the bike said that cornering with it was amazing, a normal bike you have to push it hard to lean over and this one would glide around with ease.

You may be refering to the conservation of angular momentum effect? which occurs when a rotating mass is speed up or slowed down. The engine spins up clockwise so the bike trys to spin counterclockwise, but this wont occur if the engine is spinning both clockwise and counter-clockwise with a crank going each way. Conservation of angular momentum is especialy useful when jumping mx bikes, as it allows the landing orientation to be changed while in the air.

Unless there also some sort of gyro cancelation that occurs if there are two masses spining in opposite directions at the same speed?

[camchain]

I reckon BuddyL touched on it nicely Re rotating mass being different to reciprocating mass, (although when you combine parts that do both the effects must become related).

The example Danger refers to (as I see it) is just referring to reduced wheel weight = reduced unsprung weight which 'reciprocates' as suspension moves up and down. The fact the wheel rotates as well is an extra issue not directly related to the point being made (I reckon).

I'm not bagging any of the other interesting stuff being raised - I got my first good example about how a big 4-banger doesn't like turning when I rode a new TT600 when they came out (I was riding 250 2t at the time). I thought the thing changed direction like a bulldozer. (Sorry danger no offence, I think you had one of these beasts!?)

[Danger]

No need to appologise Camchain for expressing your opinion, I won't give bad gas as others have to me for expressing my opinion on how a certain bike handles.

Now I know my KTM200 and my RM250 are a couple of the most nimble bikes out there for the sort of riding I'm doing these days, but back then I was racing YZ250's and the TT600 on MX tracks and I honestly cant recall having any issues with the handling of the TT600 but the YZ's were also known as stable handlers rather than quick handlers like the RM's off the day, so if I was to compare them to RM's back then or if I had a ride on one today I'm certain I would have noticed the lack of handling. The bike was 123kg (and I felt every kg in a wet Riverhead enduro for 5 1/2 hours) as I recall and I had the heaviest YZ490 springs I could find with the rear shock modified to use the YZ spring and I do know it was incredibly stable, controllable and was great for sliding (even on the asphalt) getting holeshots and wheelies and very tractable. In my opinion the big four stroke and its ability to hole shot back then made up a great deal for an average rider and I got some great results on that bike, not so great when racing the YZ250's which took more skill to get the most out off. I have great memory's of that bike other than its problematic electrics that used to kill the bike at times mid race (thankfully never over any jumps). Its my opinion that the new 450's have made many riders look better than what they actually are and if I was racing MX seriously thats what I would be riding today.

Incidentally the remarks on the lighter wheels on the big cruiser reducing reciprocating mass were made on Bike Rider TV last night and I did laugh at the time.

[camchain]

Thanks Danger. My bike testing analysis would probably be on a par with that TV show, vaporous like bad gas. Hopping off the 2t at the local track I just remember finding it ungainly and had trouble with the front end tucking/pushing. Mind you I also had that 600's father, the TT500 and although fun for a while I never bonded with it, just too heavy. Sounds like you got a lot out of your early riding years. Wish I had done a lot more racing. Am same weight I used to be but body doesn't reciprocate as effectively as it used to.

Those new Husabergs look great, although crank seems very high to me. I hear Kawasaki looking at similar engine layout. I recall many years ago Honda tried mounting a gas tank under the engine for super low C of G (road race machine) but they couldn't get it to turn properly.

[Danger]

Interesting stuff!! I wonder if Ktm will adopt the Husaburg theories for their mainstream bikes???

Like this you mean?

[Reckless]

Where'd you get that Danger?
The 2010 models that where on here a short time ago don't show the Husaberg engine layout in the ktm? As attached. Other pics here if you haven't spotted the thread.

PS Danger I noticed they changed the radiator caps to 1.8bar from 1.4 bar on all 2smokers for more temp stability. Might do that mod on mine as it hisses a bit on Wires and on the big dipper . But wanna see how puting the compression back to standard effects it first?