Differential Averaging Transmission

[nova_robotics]

Anybody interested in new types of transmissions and geartrains?

I came up with this a couple years ago as an alternative to CVTs. The idea is the power is split between two very simple gearsets, then power is recombined by averaging both output shafts in a differential-run-backwards. This allows lots of really cool things, including a ton of forward ratios with very few mechanical parts, and free low range. I have attached a PDF if anybody is interested in the details. The configuration in the image below is of a 15 speed transmission with 6.72 first gear.



Nova Robotics - Differential Averaging Transmission.pdf

Unfortunately R&D budgets for combustion vehicle has dropped to zero, so I don't think this will ever get built.

[BuffaloJohn]

Has this been built, other than in software?

[nova_robotics]

Has this been built, other than in software?

Never been built. Probably won't be either (unless I build it). All R&D into combustion engines has dropped to zero. It's all electric vehicles now. I just thought it was a neat design because it allows crazy amounts of gear ratios with very few parts. If you add three more gears you can get up to 24 speeds, three more after that gets you to 35 speeds. Even in 24 speed configuration it's far less parts than a traditional 8 speed automatic.

It also allows very high gear ratios. Normally you'd be limited to the transmission case size for the steepest gear ratio. If you have 20" to work with, you can only fit say a 25 tooth and a 90 tooth for a ratio of 4:1. That's all you can do because you physically can't fit larger gears with more teeth into that transmission case. With this transmission you engage forward on one half, and reverse on the other half and you can achieve very high ratios in a small transmission case size. 500:1 (or even higher) is no problem.

[BuffaloJohn]

There is a post:

Homemade Lathe Headstock EXTERNAL Gearbox

which is a multi range gearbox for a lathe. How might your design work on something like this?

[nova_robotics]

which is a multi range gearbox for a lathe. How might your design work on something like this?

It would probably work fairly well. Particularly with the low range for threading. But really modern lathes (except for the giant stuff) should only come with perhaps a 2 or 3 speed gearbox. You can go on eBay/Amazon/whatever and pick up a VFD for a couple hundred bucks. Then you have infinitely variable speeds with gobs of down low torque. I have an older lathe that I just leave it in some intermediate speed and vary the VFD frequency. I'll go 6 months without ever touching the gearbox. If you don't have one you should look into it. If you do a lot of work on a lathe it will change your life. It'll run off of regular single phase power, but you need to have a 3 phase motor installed.

[Frank S]

Differential averaging is not a totally new concept Some truck manufactures have used it for decades to get 3 speeds out of the rearends. the problem there is when 1 rearend is in low and the other in high not as much torque can be transmitted to the ground. I haven't mapped out your flow chart all that well, but I suspect ther would be the same issues in your transmission especially for heavy duty truck applications Almost all modern-day big truck transmissions have to have a minimum of 2 countershafts with corresponding gears on both to be able to transmit the full amount of torque the engines can produce and as far back as the mid 1980s Mack even fore a while had triple countershafts. Epicyclic, planetary gears accomplish higher torque outputs by having 2, 3 ,4 and even more planet gears revolving around the sun gear on a carrier contained within the ring gear multiple gear selections can be achieved by having locking either the ring gear or the planet carrier or both.
I like your concept though if for nothing else an alternative to using epicyclic gearing, not sure how the multiple clutching would be achieved without being oil driven friction packs like in an automatic transmission. Perhaps it could work using synchronizing rings and dog shifting as most all manual transmission have today helical gearing would be a must for quietness and higher transmission of torque I would think, but I may be missing the mark on your design totally. All of the major Draw works manufactures for oilfield drilling rigs completely missed the concept for a 4 speed multi strand chain driven transmission for 1000 hp and above drilling rigs I designed in 1982. All that is save for one who built 3 or 4 of them but for smaller applications in the 500 HP range

[nova_robotics]

Differential averaging is not a totally new concept Some truck manufactures have used it for decades to get 3 speeds out of the rearends.

I didn't know this. Interesting. I'd actually like some more information on that. Do you know which trucks it was used on?

[Frank S]

I didn't know this. Interesting. I'd actually like some more information on that. Do you know which trucks it was used on?

Sometime in the early to mid 1960s International started installing 3 sp capable rearends in their trucks My dad used to work on a house mover's trucks that had them how this is accomplished is by installing a pair of 2 speed tandems then adding a 3 sp selector valve or switch in the case of electric you shift both into low for the low gear, both into high for the high gear. In both the low range and the high range it is allowable to lock the power divider making both axles having equal torque output. but except in snow, Ice or off road no driver should ever drive with their power dividers locked this causes excessive tire wear and lowers fuel milage. for the intermediate speed range 1 of the rearends is shifted into low and the other into high there will be a lock out valve in this range preventing the power divider to be locked
Eaton was the first differential mfg. to offer the 3 sp. But Rockwell started doing it sometime later Some of the heavy haul drivers still run 3 sp tandems I've seen the set up back in the 1990's in Kenworths Peterbilts and even in Mack. I know a guy who has a Volvo with 3 speed tridems again L-L-L, (L-H-L, H-L-H), H-H-H is the way I believe the arrangement would be. You will normally only find the 3 sp option installed with the heavier rear ends not the 34,000lb tandems or the 38,000 lb tandems but in the 44 and 52,000 lb rears the reasons for this is if you need more gear selections than you can get with and 18 sp and 2 speed rears you also need all the strength you can get to deliver the torque