Home |
Search |
Today's Posts |
|
Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
Reply |
|
LinkBack | Thread Tools | Display Modes |
#1
Posted to rec.crafts.metalworking
|
|||
|
|||
An inquiry and response. Nonpolitical
http://www.gizmag.com/steve-durnin-d...-geared/15088/
It's pretty obvious why this works at this scale. Do you have any insight into how this might work at a useful scale? --- The reason it's hard to understand as explained is because it is explained verbally with no diagrams or drawings. It is, in essence, two planetary gear drives in tandem arranged to comprise a differential. The gear reduction system in a $49.95 winch from Harbor Freight is a rather similar arrangement, except that in these the ring gears have zero speed -- actually a locked-to-frame "barrel gear" that engages both sets of sun gears. One set of sun gears has one tooth less, so differential action takes place with high ratio like 157 : 1. The reason they're so ungodly noisy is because they don't alter the tooth profiles or pitch diameters even though they change the number of teeth. Whaddya expect for 50 bux? Matter of fact, I used a Warne winch found in Mike's garage of design the Chinese copied. The Warne was vintage good stuff, cost lots. Probably made in Taiwan... I electrified my boat lift with that Warne winch. It is audible 1/4 mile away. But it works great and nobody complains though I think Mary is still slightly embarrassed. But enough about that... I'm pretty sure Mr. D's diffy uses identical ring, planet and sun gears, with the ring gears are not locked together but able to rotate at differing speeds. In any case, they declare that the assembly is a differential. A differential produces an output speed that is proportional to the difference of two input speeds. Let's consider one input as drive and the other as control, where the speed of the control input can be conveniently, easily and efficiently varied from 0 to +/- the drive speed, which suggests the possibility of reverse at 65 mph in the US and far more in Europe. Toyota thought it had problems with a sticky gas pedal! After devining or being told which input is "drive" and which is "control", a key question then becomes: how much power must the control input have? Mr. D feels that it would be quite small, "order of magnitude" smaller than drive. Dayum, where's my checkbook and how do I invest? Let's consider a perfectly efficient system with two inputs and one output where the output speed is equal to the difference between the input speeds as Sout = S1 - S2. Now let's look at power. Pout = P1 + P2 by whichever law of thermogodammics makes me right. P2 could be negative, which doesn't violate the perfectly efficient system assumption if it somehow routes its power back to the prime mover. Easy peasy with electric motors that can also generate, but then we don' need no steenkin' variable speed tranny any more than we do in a 3000 HP diesel-electric locomotive. Let's assume this gizmo is arranged to make both input powers positive in "forward gear" since the definition of "forward" is arbitrary. Power is proportional to torque * speed, P = T*S Pout = P1 + P2 = S1*T1 + S2*T2 = Sout*Tout = (S1 - S2) * Tout but Tout= (S1*T1 + S2*T2)/(S1-S2) so T2 is inversely proportional to S2 for given Pout. I've skipped a few steps here but I think the path to conclusion is clear. As output speed approaches zero the input powers approach equality because their speeds approach equality. It can git down and grunt in the mud, deliver "ratio" even though no gear ratios have changed, provided that the "control" input can deliver nearly half of the power. That would be the variable speed control input. Non-electric, since we don' need no steenkin' variable-speed tranny in an electric system. Wonder how that works... :) |
#2
Posted to rec.crafts.metalworking
|
|||
|
|||
An inquiry and response. Nonpolitical
On May 17, 12:51*am, Don Foreman
wrote: http://www.gizmag.com/steve-durnin-d...itely-variable... It's pretty obvious why this works at this scale. *Do you have any insight into how this might work at a useful scale? --- The reason it's hard to understand as explained is because it is explained verbally with no diagrams or drawings. * It is, in essence, two planetary gear drives in tandem arranged to comprise a differential. * The gear reduction system in a $49.95 winch from Harbor Freight is a rather similar arrangement, except that in these the ring gears have zero speed -- actually a locked-to-frame *"barrel gear" that engages both sets of sun gears. *One *set of sun gears has one tooth less, so differential action takes place with high ratio like 157 : 1. * The reason they're so ungodly noisy is because they don't alter the tooth profiles or pitch diameters even though they change the number of teeth. *Whaddya expect for 50 bux? *Matter of fact, I used a Warne winch found in Mike's garage of *design the Chinese copied. *The Warne was vintage good stuff, cost lots. *Probably made in Taiwan... * I electrified my boat lift with that Warne winch. *It is audible 1/4 mile away. *But it works great and nobody complains though I think Mary is still slightly embarrassed. *But enough about that... I'm pretty sure Mr. D's diffy uses identical ring, planet and sun gears, with the ring gears are not locked together but able to rotate at differing speeds. *In any case, they declare that the assembly is a differential. * A differential produces an output speed that is proportional to the difference of two input speeds. * Let's consider one input as drive and the other as control, where the speed of the control input can be conveniently, easily and efficiently varied from 0 to +/- the drive speed, which suggests the possibility of reverse at 65 mph in the US and far more in Europe. *Toyota thought it had problems with a sticky gas pedal! * After devining or being told which input is "drive" and which is "control", a key question then becomes: how much power must the control input have? * Mr. D *feels that it would be quite small, "order of magnitude" smaller than drive. * Dayum, where's my checkbook and how do I invest? * * Let's consider a *perfectly efficient system with two inputs and one output where the output speed is equal to the difference between the input speeds as *Sout = S1 - S2. * Now let's look at power. *Pout = P1 + P2 by whichever law of thermogodammics makes me right. *P2 could be negative, *which doesn't violate the perfectly efficient system assumption if it somehow routes its power back to the prime mover. * Easy peasy with electric motors that can also generate, but then we don' need no steenkin' variable speed tranny any more than we do in a 3000 HP *diesel-electric locomotive. Let's assume this gizmo is arranged to make both input powers positive in "forward gear" *since the definition of "forward" is arbitrary. * * Power is proportional to torque * speed, *P = T*S Pout = P1 + P2 = *S1*T1 + S2*T2 = Sout*Tout = (S1 - S2) * Tout but *Tout= (S1*T1 + S2*T2)/(S1-S2) so T2 is *inversely proportional to S2 for given Pout. I've skipped a few steps here but I think the path to conclusion is clear. As output speed approaches zero the input powers *approach equality because their speeds approach equality. * It can git down and grunt in the mud, deliver "ratio" even though no gear ratios have changed, provided that the "control" input can deliver nearly half of the power. * *That would be the variable speed control input. Non-electric, since we don' need no steenkin' variable-speed tranny in an electric system. *Wonder how that works... * *:) Don, Think about sending power into a differential. One output side drives a gear reduction, one output side drives a geared step-up. Take these two outputs and ( one geared down, one geared up) and combine them with another differential. The power will take the path of least resistance, and drive the final load through the step-down side. Unless--- You either lock the step down path, and force the power to go through the step up path, or you force the step up path to move, perhaps by using a small Input driver.. I've seen such a plan with a brake on the step down path. Applying the brake (to the reduction side)causes a speed up of the output. You get infinitely variable drive, by splitting the power path into fast and slow paths, forcing the power to go through one or the other, and combining the result with another differential. So, instead of combining two power sources with a differential, you split the primary power with a differential, and force the path that the power takes with the control system. The control system can be adding or subtracting power, but that can also be re-circulated back into the system. So, a variable drive might not be as efficient as you need, but the (inefficient) variable drive does not have to handle all the power. More discussion he http://www.practicalmachinist.com/vb...ission-204359/ |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
a response to a sci.electronics.repair retard's response. | Electronics Repair | |||
Strength of Glue - Inquiry | Woodworking | |||
subpanel inquiry (yet another) | Home Repair | |||
Response 400 answer machine - no response | Electronics Repair | |||
Tool Inquiry | Woodturning |