2 Speed Gearbox

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EV2Go
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2 Speed Gearbox

Post by EV2Go » Thu, 19 Mar 2009, 00:33

Been a thinking.... As the EV scene gains maturity, we are likely to see “necessity” the mother of all invention, deliver a whole heap of products that are probably not available today.

Which got me to thinking... How to solve the conundrum of going direct drive or having a gearbox.

If you go direct drive you might wind up with a more expense or bigger motor than you might optimally want (weight, size, cost etc).

If you use a gearbox, you are faced with additional weight, mechanical losses, decreased available space, clutch issue if you want an acceptable gear change.

What would be ideal would be something in-between...

A non complicated 2 speed gearbox. I did a bit of a search to see what I could come up with and found this http://www.dimontegroup.com/Our_Work/Ou ... earbox.htm\
not quite what I was looking for but is along the right lines.

What I see as a EV must of the future is a simple no fuss 2 speed gearbox that eliminates current limitations.

Something that doesn’t require a clutch for quick gear changes (yes you can change gears without a clutch but it isn’t what you would call “fast”)
Something that doesn’t require a complicated gear shifter and associated rods etc (preferably something cable or electrically shifted to allow multiple installation positions)
Something compact and not too bulky with a big bell housing
Something that is suited to being bolted up directly to a range of popular motors bolt patterns and shaft sizes (obvious not all at once) or maybe as a stand alone unit
Something light(ish) weight as weight is an EVs biggest enemy
Something strong enough to put behind even the torquiest of motors

Well there we go, who thinks they have what it takes to go into production? Geoff? Anyone?
Last edited by EV2Go on Wed, 18 Mar 2009, 13:35, edited 1 time in total.

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Post by Tritium_James » Thu, 19 Mar 2009, 01:11

Sounds good. While we are in 'nice to have' mode: the quick shifting with no clutch problem can be handled with an additional geartooth sensor on the output shaft of the gearbox, and some smart software in the motor controller. It should be possible to use the motor controller to syncronise the motor speed with the gear you're about to shift into, for a perfect match. It needs to know motor speed (it has this already for an AC motor), the output shaft speed, and the gear ratios. It should be possible to do it really quickly too, after all, you've got the full motor power available (drive and regen) and the only thing it has to get up (or down) to speed is the motor shaft itself.

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Richo
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Post by Richo » Thu, 19 Mar 2009, 01:33

I was more thinking 3-speed in a planetary config.
So is approx the dia of the motor with no offsets.
Electronic control would be good.
So the short answer is NO but the long answer is YES.
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Post by Electrocycle » Thu, 19 Mar 2009, 04:54

I reckon a single stage planetary 2:1 reduction would be good.
You could switch between direct and 2:1 easily and have no losses in direct mode.
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Post by AMPrentice » Thu, 19 Mar 2009, 06:21

how about a modified 2 speed powerglide for RWD?
All the parts are still available off the shelf and super tough.
It could be redesigned with a compact oil sump and add a removable
bellhousing to suit different motors.

Its being done by this dude....
PoorMan EV

Here is his webpage

http://www.poormansev.com/

the powerglide mods section

Powerglide 2 speed

Has no torque convertor and most of its guts are gone

For a front wheel drive it needs to be like the metric mind one
but stronger I suppose.
Last edited by AMPrentice on Wed, 18 Mar 2009, 19:26, edited 1 time in total.
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Post by acmotor » Thu, 19 Mar 2009, 09:09

Now if you are into AMPS, you have got to be impressed by that !

At $4,000 per tonne for copper, you'd never be throwing that EV away ! Image

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Post by EV2Go » Thu, 19 Mar 2009, 16:19

Andrew is more in sync with what I am thinking... Since matching a gearbox to a motor is whole different ball game to matching it to an engine, I am looking for a way to reduce parts, cost and simplify the whole concept.

My ex boss used to make modified Glides for drag racing and used a tap instead of a converter, but that’s not what I talking about.

I am talking about the sort of gearbox that can be produced cheaply and on mass. Maybe even to the point where those with a well decked out workshop could make it themselves.

The moment you try to introduce a third gear it involves a far more complicated shifter, as it is no longer just backwards and forwards it now involves shifter sideways movement and you may as well modify an existing 3 speed.

No I am talking about a really small box that can be located anywhere, maybe even bolted directly to the motor, something like a 2 cog reduction box but with a second gear.

Last night I came up with a basic idea...

40T constant meshed 60T
Dog toothed – shaft joined
60T meshed but not constant 40T
Splined shaft

The 60T bottom left (internal splined) would sit on a splined output shaft, so it could rotate with the output shaft, but also slide up and down the length of the output shaft.

The output shaft would also have a spigot at the non output shaft end, which would sit inside the input shaft, with a needle roller bearing to provide support for both the input and the output shaft.

When the 60T cog (bottom left) is in one position it would be meshed with the 40T cog (bottom right) for gear reduction / increase (which ever doesn’t matter)

When the 60T cog (bottom left) is moved down the shaft it disengages the mesh with the 40T cog (bottom right) and engages with the 40T cog (top left) via dog gears on the side of both the 40T cog (top left) and the 60T cog (bottom left)

Would need some kind of basic slide to engage and disengage, but this could be done in a very compact square case.

Only 3 seals to leak, the input shaft seal, the output shaft seal and the selector fork seal.
Last edited by EV2Go on Thu, 19 Mar 2009, 05:20, edited 1 time in total.

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Post by AMPrentice » Sun, 22 Mar 2009, 20:43

You make it and we buy it!! wouldnt the cogs cost a fair bit?

I was leaning originally to a larger snowmobile design.
However I dont know if there are industrial belts available
or an industrial cvt that could be used already out there?
Last edited by AMPrentice on Sun, 22 Mar 2009, 09:46, edited 1 time in total.
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Post by AMPrentice » Mon, 23 Mar 2009, 06:54

Just been hunting through and found a 2 speed gearbox for circle racing but more like a Munchie in operation.
Doug nash 2 speed
Image

Obviously no reverse and thats even better for a lightweight design.
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Post by Taffy » Mon, 23 Mar 2009, 15:48

I was doing some calcs, Straight to drive gets me to around ~110kph(alot guessimation in that (100-140kph top speed)) but a two speed gear box would give 2 things. Faster acceleration and a higher top speed (assuming the gearings allows the motor so spin slower).
Making a gear box is a little outside the scope of what i am planning for rev 1, maybe in rev 2!

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Post by EV2Go » Mon, 23 Mar 2009, 17:10

Something like the DNE (Doug Nash Engineering) box would be ideal (Kind of bizarre that they made a two speed since they are famous for their 4+1 and 5+1 boxes, they even built a 4+3 for Corvettes many years ago)

That is more like the small size I had in mind, but maybe without the typical input shaft. Also ideally it would be designed to change gears without a clutch.

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Post by Goombi » Tue, 24 Mar 2009, 06:03

Hello Everyone
What would it cost to make a 2 speed g/box? What gear 2-5 th 3-5th How much lighter will the gearbox be? 5 kg? where is the bellhousing? Engine mounts? Hmm simplicity is a way to go 5 speed gearbox ans sometime you will need first gear and only 3 rd and 5 th plus reverse
I do not like to look like a sceptic but is it going to be practical?


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Post by EV2Go » Tue, 24 Mar 2009, 22:30

The purpose of the thread is to stimulate new thinking instead of tired old revamped ICE thinking.

Even if you took a few gears out of an ICE box (no pun intended) you still have many of the limitations, such as an input shaft that is designed to take a clutch, a long gearbox length that can only be located in a transmission tunnel, a gear set that was designed to be used in conjunction with a clutch, extra weight...

I am try to stimulate out of the box thinking, something designed specifically for EVs, limited gears to take the burden off a direct drive, light weight, small dimensions so it can be located in a number of places, i.e in the usual transmission spot, mid mounted motor, FWD etc. Designed without a clutch in mind for easier gear changes, so no bulky bell housing required, something that would slip straight over a motor output shaft...

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Post by Electrocycle » Wed, 25 Mar 2009, 01:02

yeah I think something could be made that'd essentially just lengthen the motor by 75-100mm
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Post by Richo » Wed, 25 Mar 2009, 05:33

An oversized version of THIS would be good Image
So the short answer is NO but the long answer is YES.
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Post by stuartri » Wed, 25 Mar 2009, 06:18

To all this maybe a little left of centre but there is a technology developed by NuVinci, CVP technology that has real promise. I am using the bike version on my electric vehicle that I race. No clutch required, 0.5 underdrive to 1.75 overdrive. Uses an idler that can be cable or electronically controlled and is part of wheel assembly. I believe they have adapted the bike technology to cars.

Regards Stuart

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Post by BG » Wed, 25 Mar 2009, 06:23

This is something I'm looking into further. Gearboxes are this kind of swings and roundabouts thing..
The cogs cost a fair bit - about $1500 each to get 1-offs made!! The other thing to consider is you still need a differential (unless you have two motors) so the idea of a 'gearmotor' doesn't make as much sense as you'd first hope- still need to connect it to the final drive somewhere. Also a 'Park' lock would be nice.. for those cars with bad handbrakes!

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Post by AMPrentice » Wed, 25 Mar 2009, 07:39

If somehow Winters Quickchange could be swapped on the fly Image

So far the only solution is direct drive with a big enough motor.
Eventually some1 will make something happen even a motor supplier maybe.
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Post by Taffy » Wed, 25 Mar 2009, 14:47

Hey Stuart,

Do you have any more info on this? (size, photos, difficulty of set up?) I was part of electric race team last year (SAE demo car) and they would be very interested in this.
I would be very interested into this for my lotus 7 build as well Image

Cheers
Taffy

edit: From here: http://wikicars.org/en/Continuously_Var ... ansmission

A list of "old" cars with CVT

DAF 600
DAF 750
DAF 30 (Daffodil)
DAF 31
DAF 32 (DAF 33)
DAF 44
DAF 46
DAF 66
Fiat Uno
Ford Fiesta
Honda Civic ESi
Nissan Micra
Subaru Justy 1.2 3 cyl with ECVT (49/55 kW)
Volvo 66
Volvo 340
Daewoo (currently GM Daewoo) Matiz II with E3CVT

Another link: http://www.mitsubishi-motors.com/corpor ... e/cvt.html
Mitsubishi Lancer
Mitsubishi Colt
Mitsubishi Dion

A 2 speed belt CVT has me interested, possible more for a EV Go Kart then the car for now though.
Last edited by Taffy on Wed, 25 Mar 2009, 04:22, edited 1 time in total.

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Post by AMPrentice » Wed, 25 Mar 2009, 15:55

The DAF versions and Snowmobile types are the simplest ones that could be made.
However the belts are expensive last I checked to rebuild an Old DAF I was interested in buying years ago.

A snowmobile version like below, made beefier would be the go for CVT.
Image
Last edited by AMPrentice on Wed, 25 Mar 2009, 04:56, edited 1 time in total.
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Post by Goombi » Wed, 25 Mar 2009, 16:56

I say--- Why have it simple when we can enjoy the complications
Why would anyone sideline the Automotive invention of a 5 speed Synchronise Gearbox? If this exercise is purely for Brain Stimulation then i am in a loony house ----what a lot of CODSWALLOP

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Post by Johny » Wed, 25 Mar 2009, 17:23

I haven't heard that term for a long time Goombi.
Why not unsubscribe from any threads that upset you?
The 2 speed gearbox idea is a next-step for those that find direct drive just a bit limiting. It has a lot of merit and really does not require justification.

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Post by Taffy » Wed, 25 Mar 2009, 17:47

I am building my EV to be close to IC performance with a sane budget as i can. If a gearbox can help me to get that then i am interested in exploring the possibilites even if they end in complications. I want to push past 110kph with ease (private rd, track days, hill climbs etc)

I am currently doing direct drive but if it was possible to use a quick shift 2/3 speed with 1:0.75 1:1 1:1.5 or something similar i would be very intersted.

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Post by fuzzy-hair-man » Wed, 25 Mar 2009, 19:58

Electrocycle wrote: I reckon a single stage planetary 2:1 reduction would be good.
You could switch between direct and 2:1 easily and have no losses in direct mode.
Do you mean these things?

Image

Looking at they they would be quite compact and you could imagine one bolting up to the back of a motor.
Wiki article on Epicyclic gears

According to the above you can change ratios by which component you hold stationary so it would also give you a couple of gears and I imagine 1:1 if you lock the whole thing up, which is what you were saying right?

Any ideas on the efficiency of these?

I was also thinking what chiefly determines the efficiency of a drive train? Is it the overall reduction or is it the number of reduction steps? ie is a 2:1 in a gearbox then a 3:1 at the diff likely to be more or less efficient than a 6:1 reduction at the diff? I'd expect a single reduction is likely to be more efficient in which case would it be better off trying to integrate this 2 speed gearbox into the diff seeing as we are still going to need a diff?

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Post by Electrocycle » Wed, 25 Mar 2009, 20:36

yep that's exactly what I mean :)

It's not hard to add a dog system to switch the output shaft between the input shaft and the gear carrier, for a simple 2 speed box that's very compact.
Parts wise, it's basically just one stage from an auto transmission, so it'd be easy to get hold of the gears.

I think the efficiency will depend on a number of factors:

* number of stages
* power being transmitted (high rpm or high torque will increase losses)
* gear size (contact area)
* tooth design (helical teeth will be quieter but have more frictional losses)

Combining everything with the diff would be ideal, but it adds several levels of complexity to a custom built item.
A simple in line 2 speed gearbox that's easily adaptable to various motors allows you to build the car as if it was direct drive, but with half the motor torque requirement, or a narrower usable power band.

For a front wheel drive car I think you're best off using the car's original gearbox because they are quite compact and contain the diff - but for RWD it'd be great to mount the motor and small gearbox where the car's original gearbox was.

Ideally I'd like to run two motors with their own reduction drives and get rid of the diff entirely.

A CVT transmission would also be very good.
I'd like to build an EV using a CVT donor vehicle.
Last edited by Electrocycle on Wed, 25 Mar 2009, 09:39, edited 1 time in total.
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