How does 2 speed nitro transmission work?

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gandalfnz

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Hi Guys

I am trying to figure out the OWB part of the 2 speed transmission. The centrifugal part I understand.
What confuses me is that OWB that is located always in the first gear.
Does that mean that the car is driven in 1st gear by OWB locking onto the shaft, and if the bearing is bad, it would just slip and car would not move?
Also, once shift RPM is reached, then both 1 and 2nd gears are engaged at the same time, because shaft still spins in the same rotation, and 1st gear OWB will still be engaged?

Friends nitro car is not taking off, barely gets any traction, we focused on the clutch, which we replaced with a brand new one.
I noticed that when I hold 1st and 2nd spur gear by hand, I can roll the car backwards and forward with barely any resistance.
Does this mean transmission OWB is buggered?

I think I discussed this before with tudordewolf on this forum, but is till confuses the heck out of me.

Please help me fully understand this.
 

tudordewolf

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Does that mean that the car is driven in 1st gear by OWB locking onto the shaft, and if the bearing is bad, it would just slip and car would not move?
Yes
Also, once shift RPM is reached, then both 1 and 2nd gears are engaged at the same time, because shaft still spins in the same rotation, and 1st gear OWB will still be engaged?
No - the direction of the OWB is such that when second gear engages, the shaft is turning faster than first gear, which is the direction the OWB allows - it doesn't allow the shaft to turn slower than first, or backwards, which is why rolling it backwards spins the transmission, unless:
I noticed that when I hold 1st and 2nd spur gear by hand, I can roll the car backwards and forward with barely any resistance.
in which case:
Does this mean transmission OWB is buggered?
Probably
 

cbaker65

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Hi Guys

I am trying to figure out the OWB part of the 2 speed transmission. The centrifugal part I understand.
What confuses me is that OWB that is located always in the first gear.
Does that mean that the car is driven in 1st gear by OWB locking onto the shaft, and if the bearing is bad, it would just slip and car would not move?
Also, once shift RPM is reached, then both 1 and 2nd gears are engaged at the same time, because shaft still spins in the same rotation, and 1st gear OWB will still be engaged?

Friends nitro car is not taking off, barely gets any traction, we focused on the clutch, which we replaced with a brand new one.
I noticed that when I hold 1st and 2nd spur gear by hand, I can roll the car backwards and forward with barely any resistance.
Does this mean transmission OWB is buggered?

I think I discussed this before with tudordewolf on this forum, but is till confuses the heck out of me.

Please help me fully understand this.

Yes it does ,a trans o-way can't have no lube or any other contaminants in them or they
will fry ,such as trans grease or fuel that may have been slung in them ,cars o-way set
up may varry from an MT. ,but once a o-way bearing starts to slip on the shaft ,they are toast!
 

olds97_lss

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Yes it does ,a trans o-way can't have no lube or any other contaminants in them or they
will fry ,such as trans grease or fuel that may have been slung in them ,cars o-way set
up may varry from an MT. ,but once a o-way bearing starts to slip on the shaft ,they are toast!
I always put a bit of oil on mine, just light 3-in-1 or something similar. No grease though.

Strangely, in all the years of running nitro MT's, I think I only had one trans owb go bad on me. Quite a few engine owb's though. Guessing the higher rpm's and castor oil tend to take their toll on them in the engines, especially if they were internal vs external.
 

gandalfnz

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No - the direction of the OWB is such that when second gear engages, the shaft is turning faster than first gear, which is the direction the OWB allows - it doesn't allow the shaft to turn slower than first, or backwards, which is why rolling it backwards spins the transmission, unless:

Thank you for explaining this.
This is where my "mechanical" mind is failing me, if the shaft maintains the same spinning direction, in both 1st and 2nd, that means 1st OWB is still locked to the shaft, which means it spins at whatever speed the shaft spins even at the time of 2nd engagement.
I still fail to understand how 1st can freewheel when OWB still locks it in.

Thanks
Yes it does ,a trans o-way can't have no lube or any other contaminants in them or they
will fry ,such as trans grease or fuel that may have been slung in them ,cars o-way set
up may varry from an MT. ,but once a o-way bearing starts to slip on the shaft ,they are toast!

I am pretty sure OWB is bad as you say, car barely moves at all.
I myself also have never had a bad tranny OWB.
I always put a bit of oil on mine, just light 3-in-1 or something similar. No grease though.

Strangely, in all the years of running nitro MT's, I think I only had one trans owb go bad on me. Quite a few engine owb's though. Guessing the higher rpm's and castor oil tend to take their toll on them in the engines, especially if they were internal vs external.

He has installed a race engine on this car, its a 4.6 losi engine or something, quite powerful, I am thinking this is what just destroyed the OWB.
 

tudordewolf

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This is where my "mechanical" mind is failing me, if the shaft maintains the same spinning direction, in both 1st and 2nd, that means 1st OWB is still locked to the shaft, which means it spins at whatever speed the shaft spins even at the time of 2nd engagement.
I still fail to understand how 1st can freewheel when OWB still locks it in.

The one-way bearing acts like a mechanical diode, its behavior is determined by the difference in angular velocities, not just the inner shaft's motion. If X is first gear RPM and Y is shaft RPM, the OWB just enforces the relationship Y X. Shaft RPM is greater than gear RPM when freewheeling or in second gear, and equal when in first gear. The shaft "slips out" of the OWB's grip when second engages because something else (second gear) is pushing the shaft faster than the one-way bearing.

It's like if you were using a ratcheting wrench to turn a bolt, and somehow the bolt began turning faster than the wrench - it would be free to spin the mechanism in the forward direction, regardless of how you moved the ratchet on your end (except for flipping its direction, but the OWB in a nitro is always facing the same way). There are ratchets that use OWB's instead of the usual gear and pawl, which claim to have an almost infinitely fine "step", and which suffer the same issues arising in this thread...
 
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gandalfnz

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The one-way bearing acts like a mechanical diode, its behavior is determined by the difference in angular velocities, not just the inner shaft's motion. If X is first gear RPM and Y is shaft RPM, the OWB just enforces the relationship Y X. Shaft RPM is greater than gear RPM when freewheeling or in second gear, and equal when in first gear. The shaft "slips out" of the OWB's grip when second engages because something else (second gear) is pushing the shaft faster than the one-way bearing.

It's like if you were using a ratcheting wrench to turn a bolt, and somehow the bolt began turning faster than the wrench - it would be free to spin the mechanism in the forward direction, regardless of how you moved the ratchet on your end (except for flipping its direction, but the OWB in a nitro is always facing the same way). There are ratchets that use OWB's instead of the usual gear and pawl, which claim to have an almost infinitely fine "step", and which suffer the same issues arising in this thread...

Thank you very much for explaining this in such detail.
Been sitting at work with at ratchet in my hand trying to figure this thing out, and I finally did.
LOL I had a bolt in it and all, and yes, if I spin the bolt faster in the same direction as I as tightening, there is no ratchet engagement.
WOW, thanks again!

I had a go and my friends car last night again, once I removed the tranny, I could not force spin/slip the OWB.
Which leads me to believe his diffs have taken a hit?
 

cbaker65

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Thank you very much for explaining this in such detail.
Been sitting at work with at ratchet in my hand trying to figure this thing out, and I finally did.
LOL I had a bolt in it and all, and yes, if I spin the bolt faster in the same direction as I as tightening, there is no ratchet engagement.
WOW, thanks again!

I had a go and my friends car last night again, once I removed the tranny, I could not force spin/slip the OWB.
Which leads me to believe his diffs have taken a hit?

Usually you want to check all the small stuff before assuming it is in the trans ,like wheel pins ,set screws in axles
or drive shafts!
 

olds97_lss

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Thank you very much for explaining this in such detail.
Been sitting at work with at ratchet in my hand trying to figure this thing out, and I finally did.
LOL I had a bolt in it and all, and yes, if I spin the bolt faster in the same direction as I as tightening, there is no ratchet engagement.
WOW, thanks again!

I had a go and my friends car last night again, once I removed the tranny, I could not force spin/slip the OWB.
Which leads me to believe his diffs have taken a hit?

I have a similar issue figuring out how wankle engines transfer power and the "piston" rotates properly to do so... but that's another thread for another day. lol!

Do you know the brand/model of the car your having issues with? Can you post some clear photo's of the chassis with the body off? Knowing what you have may help us help you.
 

gandalfnz

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Hi

He has Hot Bodies Nissan 1/7 scale.
This one

https://www.bigsquidrc.com/reviews/hot_bodies_ls.php

We keep arguing what it is, I have never seen such a problem before.
If you hold both gears with your finger, car will roll back and forth with barely any resistance at all.
Remove the clutch, I cannot spin the first gear by hand once removed, so OWB locks well, at least I think so.
To me, it can only be either the tranny (which we think is OK) or diffs....
 

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