Brumby gearbox ratios? (5 or 4 speed)

Thalass · Post by **Thalass** » Mon May 25, 2009 3:07 pm

On the electric car forum I frequent there's been discussion about two speed gearboxes for EVs that would otherwise be direct drive. Those cars that do keep the gearbox tend to only use 3rd and 5th or 2nd and 4th gears. And even then you usually leave it in that gear - low for city driving, high for highway.

Now I plan on using two motors directly driving two diffs - one at the front and one at the back - but I'd also like to take my brumby off road after the conversion, and it's been suggested that rather fork out for two smaller two speed gearboxes I might as well keep the original box if I want to go off road. And it's a good point. Even with the better torque at low rpm I still can't really imagine tackling the powerlines track in what is effectively 5th gear.

The problem is that gearboxes and I don't really get along, which is why I wanted to chuck it away in the first place, but it is a valid point so I went searching for info on the gear ratios in the old boxes. But I can't find anything.

So what do you guys think? Perhaps I could keep the transfer case and just use low/high range? Or somehow just use 4th and 3rd or whatever, plus 4wd/4wd low. Either way I'm going to pull the car to pieces so it's not much extra effort. I'd need one bigger motor then, but that'd probably be easier than two smaller ones.

Still waiting for the house to be built!

Phizinza · Post by **Phizinza** » Mon May 25, 2009 6:15 pm

Why not put a 5sp 3.9 ratio from an L series in it. Then only use the gear that works best onroad for what ever but keep the other gears as an option offroad. I can imagine 1st with low range and electric motors would be very nice offroad.

the 4sp D/R boxes came in both 3.7 and 3.9 ratio. Its random which ratio came in you car but after 84 I think all Brumby's came with 3.7 4sp D/R's.
Its similar with the 5sp in the L series. Just random. It appares that your more likely to find a 3.9 ratio in a 85 or 86 touring wagon then anything else though. And sportswagons might only come in 3.7 from factory, but I'm not sure on that.

mattl200 · Post by **mattl200** » Mon May 25, 2009 6:30 pm

why not keep the two rear diffs idea and use a transfer case from a serria
or a hilux or landcruser depending on how big the motor is
ie 2 speed gbox and the low ratio can be changed to sute your needs
heaps of companys make lowrange gearsets for these transfer cases
with ratios down to about 200to1 i think thats caluclated in 1st though

i have both serria and hilux in the shed if you want pics

and 4 or 5spd top gear is overdrive 5 spd is a little higher from memory

edit : just thought more about this and realised you would want awd
now thinking pajaro superselect transfercase
ie rwd, awd high low, 4wd high low
but i think its computer controled witch could be good or bad power requirements vs having a switch on the dash for a selector

Thalass · Post by **Thalass** » Tue May 26, 2009 6:28 pm

I would like to keep things simple, mechanically, which is why I was going for the two motors option. And yeah I'd prefer permanent AWD if possible, but I guess I'll figure it out eventually.

Would a hilux transfer case fit in a brumby? haha. Sierra might be ok, they were the miniature jeep style things, weren't they?

I think if I had an unlimited budget I'd get a pair of rock-crawler 3 speed boxes made up. With high, medium, and low speed being 1:1, 3:1 and, I dunno, 5:1? something like that. But then I'd probably have to stop to change gears or something.

BaronVonChickenPants · Post by **BaronVonChickenPants** » Tue May 26, 2009 7:14 pm

The problem with the transfer case idea is you then need to factor in the centre diff (wasn't that a debacle last time I brought it up) so it would need to be an AWD transfer case, possibly lockable then all of a sudden it's getting complex again.

That being said, i can't think of a simple lightweight solution for the 2 motor setup, especially something that needs to handle the potential torque of offroading.

Maybe have a look at the transfer case section of a Subaru 4EAT, Subarino has just finished playing with a lockable centre diff mod, see if maybe it could be sealed up so that it can be run without the rest of the gearbox...I'm not that familiar with these, not sure if they have hi/lo range or just straight through.....I think I'm babbling now, I'll ponder this some more and get back to you....

Jordan.

YouTube · Post by **El_Freddo** » Tue May 26, 2009 9:45 pm

Or look into the divorced hi/lo, lockable AWD transfer case of the Lada Niva's. I reckon you'd be able to position it nice and close to the front diff with the motor mounted above it, running a longer tail shaft down to the rear diff. That should be the simple device you're after. I know of two at a wreckers in melbourne last time I was there, dunno what they're asking though (and you're in Perth...).

This is the same idea that Andrew T was toying with for his monster wagon, but used in a different way to your application needs.

Food for thought.

Cheers

Bennie

Phizinza · Post by **Phizinza** » Tue May 26, 2009 11:31 pm

^^

That's a thought I just had, using only a transfer case so you have two gears, 1:1 and 2.XX:1. Would be a very simple setup too.

Thalass · Post by **Thalass** » Thu May 28, 2009 4:36 am

El_Freddo wrote:Lada Niva

Eeeeuch. My dad had a niva when I was a kid. I think he gave up on it after about 18 months. He had to change the gearbox two or three times!

But that is a good idea. This suzuki has the induction motor straight on to the Sierra's transfer case. In the drivetrain section he lists 10.5:1 motor to wheels in low range, and his graphs (on the aeva forums) show momentary 300nm of torque.

I'm starting to think this is the best setup, but a 6.5:1 high range ratio may not be so good for on-road.

Phizinza · Post by **Phizinza** » Thu May 28, 2009 10:12 am

Well with Subaru diffs you can have 3.7 or 3.9 to one reduction in the diff. High range in the case should be 1:1. Then with a suzi t case you can have standard 1.9(?) to 1 or you can buy 4:1, 6:1, 8:1 reduction low range gears.

Thalass · Post by **Thalass** » Thu May 28, 2009 11:03 am

This sounds like the way to go. Would the transfer case be 4WD or AWD?

3.9 brumby diff + 4:1 transfer case = 15.6:1 total low range?

vincentvega · Post by **vincentvega** » Thu May 28, 2009 12:20 pm

I think you are underestimating the amount of low RPM torque you are going to have available for use offroad. You won't need anywhere near as low gearing as you would for a combustion engine

AndrewT · Post by **AndrewT** » Thu May 28, 2009 3:26 pm

Surely the easiest thing to do (in a Subaru) would be to use 1 electric motor just adapted to the existing 4x4 gearbox? The natural upgrade to L series 5speed would still be a good one over the original 4speed.

mattl200 · Post by **mattl200** » Thu May 28, 2009 8:36 pm

the zook transfer is rwd or 4wd
so is the hilux but phisically about the same size and stronger

the lux transfer removed from the gbox could be coupled direct to the motor would need a splined adaptor to your motor and adaptor plate (im thinking direct coupled here not clutch that would require more design)
if the motor fit in the tunnel then it could be placed furthur back to give a bit more even weight distribution and mor room in the engine bay for the rest if the gear
the ev's ive seen seem to be pretty cramped in there

Phizinza · Post by **Phizinza** » Thu May 28, 2009 10:28 pm

Thalass wrote:This sounds like the way to go. Would the transfer case be 4WD or AWD?

3.9 brumby diff + 4:1 transfer case = 15.6:1 total low range?

Its refered to as a crawl ratio (gearing, low range, plus diff ratio).
Suzi's are all RWD/4WD. Most 4x4's are. Only very recently is AWD coming into play and its normally only AWD. Not sure about these Niva tcases, I always thought they were RWD/4WD, but if they are AWD lockable like old range rovers then maybe thats the way to go?
You will find most 4wd tcases are bolted to the gearbox, so finding one that is "devorced" will need some research. I assume seems the suzi ones were brought up they are devorced. I know hilux ones arent, same with landcrusier and range rovers. There are a few more but I only really know about larger 4x4's, and I'm pretty sure you want to keep it to the small stuff for weight reasons.

Thalass · Post by **Thalass** » Tue Jun 02, 2009 11:08 pm

Andrew: It would certainly be simpler from a conversion point of view. One motor, and the controller should be simpler to find, too. But there is the issue of losses (not great, but still notable), and the fact that I'd like to keep things simple mechanically.

I think for the moment I'll keep thinking about it. I'm going overseas next week for ten weeks, and then after then we'll be moving into the house so its still going to be three months before I can start thinking about buying a brumby.

An 11kw (nominal) motor with 300nm of torque (for up to 60ish seconds) certainly sounds like it would be capable off road even with direct drive to the diff. And two of them (or, say, two 8kw motors with slightly less torque) probably wouldn't have much trouble. But then again 300nm through a 17:1 crawl ratio sounds really good to me.

So I guess it's still all up in the air until I actually start buying stuff. haha!

Gannon · Post by **Gannon** » Wed Jun 03, 2009 4:18 pm

I just had an awesome thought. If you do go with 2 motors, one for front and the other for the back, you could actively control the torque split using the motor controller. Imagine sending 65% of the power to the rear and 35% to the front. Could make an interesting track car.

mattl200 · Post by **mattl200** » Fri Jun 05, 2009 7:19 pm

Phizinza wrote:Its refered to as a crawl ratio (gearing, low range, plus diff ratio).
Suzi's are all RWD/4WD. Most 4x4's are. Only very recently is AWD coming into play and its normally only AWD. Not sure about these Niva tcases, I always thought they were RWD/4WD, but if they are AWD lockable like old range rovers then maybe thats the way to go?
You will find most 4wd tcases are bolted to the gearbox, so finding one that is "devorced" will need some research. I assume seems the suzi ones were brought up they are devorced. I know hilux ones arent, same with landcrusier and range rovers. There are a few more but I only really know about larger 4x4's, and I'm pretty sure you want to keep it to the small stuff for weight reasons.

in this case it wont matter if thje trasfer is devorced or not
the hilux ones would probley be easyer to connect a motor to because it would give you somthing to mount the motor to 300nm of toque would probley destroy the mounting points

and if looking for awd transfer only look to the 80 series landcruser but i dont know how big thay are or if one would even fit
cant imagin it being much bigger than a hilux box though

Thalass · Post by **Thalass** » Sat Jun 06, 2009 12:33 am

It occured to me today that vincentvega might be right. Even if I have two smaller motors with, say, 200nm of torque each (pulling the number out of my arse), that would still be 400nm of torque from 0 rpm! Even going through a pair of 3.9 diffs surely in a brumby that would be enough!

Also Suparoo, that's a pretty good idea. If the controller is in torque control mode (which is what I'll try for) you could have a lever/knob/whatever that would alter the torque command for each motor +/- a certain amount. From say +15% to the front, -15% to the rear, or any variation. You couldn't put all the power to one motor, because you'd end up with half the total power/torque with one motor doing nothing. But it could be a good idea. Especially with one wheel in the air spinning uselessly - just send more power to the wheels on the ground.

Speaking of that, I'll have to investigate lockable diffs once I get it on the road and can start thinking of the next steps (on-board generator for usefully long range off roading, etc)