Runwell vs Zeda crank

[Lukesky36]

The angular speeds are the same, but the linear speeds are different

 

[gary55]

The angular speeds are the same, but the linear speeds are different

Think about that for a sec. Bro. If one changes how could the other not. As linier speed increases so will the angular speed. They are tied together like a rod and a journal. Not to pick bones but my thoughts wasn't on their differences, but the causes of the differences in the piston speed, and I've concluded it is due to rod weight when differing lengths are used with the same stroke. Read #29 again and see if I'm making since to you.

 

[Lukesky36]

If for say we got 2 motors running at 1000 rpm A=Long Rod B=Short Rod both have the right corresponding piston sizes the longer rod will have less side thrust as the shorter crank will have higher side thrust that would turn into more friction and less smooth operation both can have the exact same compression and cc's but i could see that longer rod engines would last more and run more smooth rod weight could be compensated by the inertia of the crank being balanced for the heavier rod. Don't mind me i'm ranting at this point

 

[gary55]

If for say we got 2 motors running at 1000 rpm A=Long Rod B=Short Rod both have the right corresponding piston sizes the longer rod will have less side thrust as the shorter crank will have higher side thrust that would turn into more friction and less smooth operation both can have the exact same compression and cc's but i could see that longer rod engines would last more and run more smooth rod weight could be compensated by the inertia of the crank being balanced for the heavier rod. Don't mind me i'm ranting at this point
View attachment 84154

Cool. That means I'm not the only one.

 

[LewieBike]

The piston speed is lower with the long rod due to the time it takes to cover the same distance and that kinda explains why PK's are known to be good at higher rpm and Zeda's make more torque.

No this is wrong, the piston speed stays exactly the same *if* the engine is using the same stroke when the crank is at 90 degrees, perpendicular to the piston and bore axis.

A longer rod only changes the angular velocity temporarily on a radiant to the angle from top dead center, plus a longer rod adds weight and vibration and piston side loading at fast RPM's

These engines would all benefit from being undersquare, in other words a real old school, long stroke, Schnerle ported 2 cycle: like 46 mm stroke with a 38~40 mm bore. With better porting and transfer times, you could have an engine that produces a wall of torque from 2000 rpm upwards. Useable torque is much more useful on a motorized bicycle.

 

[Street Ryderz]

All of this stuff gets hard to describe verbaly or writen for me, with out making an animation I dont think I can really do it.And I cant make an animation etheir LOL.I was thinking about all this thought and it occured to me that when Grubee came out with these engines it was the 38mm stroke and long rod/high pinned piston,and I think that was so as to fail at the wrist pin rather than the big end.When looking at the diagram's above the crank is further away from the cylinder to accomidate the long rod and maintain the same stroke,in our engine's the big end is in close to the center not out at the edge as in the diagram.Our cranks have the big end in very close to center and where the difference in pin location is 1mm further out from center that big end is traveling faster right? longer distance in the same time say's it faster so then what's the little end doing along with the piston,I think actually it's moving faster on the down stroke after the big end passes over the dwell point from tdc and the piston is decending it would be faster because it's traveling a farther distance but with the dwell equalizes the time so that you could say its the same speed.The up stroke deffinatly slows down IMO due to the defelction of piston and compression,When I do my balance the first weight eliminated is the rods then some of the pison to reduce the overall reciprocating mass.Now I'm rambling LOL

 

[Lukesky36]

i found a nice Brief for this discussion we been having enjoy reading What rod is better?

 

[gary55]

All of this stuff gets hard to describe verbaly or writen for me, with out making an animation I dont think I can really do it.And I cant make an animation etheir LOL.I was thinking about all this thought and it occured to me that when Grubee came out with these engines it was the 38mm stroke and long rod/high pinned piston,and I think that was so as to fail at the wrist pin rather than the big end.When looking at the diagram's above the crank is further away from the cylinder to accomidate the long rod and maintain the same stroke,in our engine's the big end is in close to the center not out at the edge as in the diagram.Our cranks have the big end in very close to center and where the difference in pin location is 1mm further out from center that big end is traveling faster right? longer distance in the same time say's it faster so then what's the little end doing along with the piston,I think actually it's moving faster on the down stroke after the big end passes over the dwell point from tdc and the piston is decending it would be faster because it's traveling a farther distance but with the dwell equalizes the time so that you could say its the same speed.The up stroke deffinatly slows down IMO due to the defelction of piston and compression,When I do my balance the first weight eliminated is the rods then some of the pison to reduce the overall reciprocating mass.Now I'm rambling LOL

When all else is equal It's the weight of the longer rod my Brother making the diff. A 223 or a 22/250 either one when added more grain weight to the projactile is going to move slower. the angularity is something , but not all that much something.

 

[gary55]

No this is wrong, the piston speed stays exactly the same *if* the engine is using the same stroke when the crank is at 90 degrees, perpendicular to the piston and bore axis.

A longer rod only changes the angular velocity temporarily on a radiant to the angle from top dead center, plus a longer rod adds weight and vibration and piston side loading at fast RPM's

These engines would all benefit from being undersquare, in other words a real old school, long stroke, Schnerle ported 2 cycle: like 46 mm stroke with a 38~40 mm bore. With better porting and transfer times, you could have an engine that produces a wall of torque from 2000 rpm upwards. Useable torque is much more useful on a motorized bicycle.

Nonsense, if the rod is longer and heavier though it has the same stroke their is no way the same charge can propel it at the same velocity as a shorter lighter rod.

 

[LewieBike]

What's nonsense? The piston speed is rising and falling continuously, but when the crank is at 90 degrees to top dead center, this is where the highest piston speed is, and if you have two engines with the same length of stroke, the piston's fastest speed at 90 degrees to TDC will be exactly the same despite the rod length.