planitary gear sets at the axle hubs
planitary gear sets at the axle hubs
(OP)
does anyone have any experience with mounting a transmission in the area of the rear axle and then elimination the ring and pinion gear and using a planetary gear set in each hub instead?
Luck is a difficult thing to verify and therefore should be tested often. - Me





RE: planitary gear sets at the axle hubs
RE: planitary gear sets at the axle hubs
European truck tractor axles have favored hub mounted planetary reductions for as long as I can remember.
rmw
RE: planitary gear sets at the axle hubs
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: planitary gear sets at the axle hubs
I'll look into what I can find on heavy trucks.
Does anyone ever use the hub mounted planetary to shift? like a two speed automatic?
Lastly unsprung weight should not be a huge issue as this will be a straight line exhibition car.
Luck is a difficult thing to verify and therefore should be tested often. - Me
RE: planitary gear sets at the axle hubs
On an earth-mover, it's quite likely that there will be enough space to do what you describe and I think at least some of them already use gear-reduction at the hubs. On a small car, that area has a lot of other stuff competing for space (brakes, wheel bearings, hub, suspension attachment points, CV joints in the case of independent suspension, etc).
It seems redundant to put a gear-change mechanism inside the hub. #1, space, weight, etc. #2, anything you do in this manner would have to be doubled (one on each side) compared to doing the same gear-change mechanism in front of the differential (in which case you only need one, and it can be integrated into the transaxle).
RE: planitary gear sets at the axle hubs
The reason I was thinking about the planetaries to reduce torque on the axles reducing their weight and rotational inertia as well as being able to create a fully floating design so a failure would not be as catastrophic. Also if I have room I could sink the motor down between the axles lowering my center of gravity and reducing weight transfer to the aft.(possibly even set up in such a way as to pull power from both ends of the shaft)
Luck is a difficult thing to verify and therefore should be tested often. - Me
RE: planitary gear sets at the axle hubs
Axle inertia would seem to be a minor contributor. When the engine gets closer to the ground a full sized flywheel can be the clearance limit.
RE: planitary gear sets at the axle hubs
RE: planitary gear sets at the axle hubs
Luck is a difficult thing to verify and therefore should be tested often. - Me
RE: planitary gear sets at the axle hubs
1) Eliminating the ring/pinion gearset is one thing, but how would you implement the differential function?
2) Reducing polar moment of inertia of axles gets you nowhere if their speed is correspondingly increased.
Will axle torques be typical "small sports car" range, or is this a hot rod? If you're talking about relatively low torque values, I'd suggest you glance at the old DAF dual V-belt arrangement, which worked "okay".
RE: planitary gear sets at the axle hubs
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: planitary gear sets at the axle hubs
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: planitary gear sets at the axle hubs
and yes it is drag racing.
Luck is a difficult thing to verify and therefore should be tested often. - Me
RE: planitary gear sets at the axle hubs
Sandy
RE: planitary gear sets at the axle hubs
RE: planitary gear sets at the axle hubs
Luck is a difficult thing to verify and therefore should be tested often. - Me
RE: planitary gear sets at the axle hubs
I don't know of anything heavier duty than an old 60s OD unit but less than a Lenco.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: planitary gear sets at the axle hubs
Luck is a difficult thing to verify and therefore should be tested often. - Me
RE: planitary gear sets at the axle hubs
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: planitary gear sets at the axle hubs
Luck is a difficult thing to verify and therefore should be tested often. - Me
RE: planitary gear sets at the axle hubs
Ed Danzer
www.danzcoinc.com
www.dehyds.com
RE: planitary gear sets at the axle hubs
Dragrace motorcycles employ a unique gearbox design which allows upshifting without power interruption. I don't remember the details of the mechanism- read about it a few years ago, and remember thinking it was quite clever. You could look into building a two-speed manual transmission with this shifting design, for your "small" car.
Higher power drag race cars (such as Pro-Stock, over 1,000 HP) have used "clutchless" dog-ring-shifting manual transmissions, like the four-speed Jerico.
A single two-speed Lenco unit is not very heavy, considering the torque capacity (1,000 ft.lb.?). It's maybe 7" diameter by about 8" long.
RE: planitary gear sets at the axle hubs
Sounds fine at first, but there are some bad side effects to this. You can no longer downshift except at a standstill, but even worse, the gears for which this has been done can no longer transmit engine braking torque. Once you have applied load to the transmission in first gear you MUST upshift through all of the subsequent gears that have had this treatment done without ever backing out of the throttle to the point that the transmission is back-driving the engine (engine braking). If you do, the transmission smashes its internals to smithereens.
RE: planitary gear sets at the axle hubs