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Discussion Starter #1
I thought I'd post a picture of what can happen with doubling the design torque through a normal transmission after a while if you drive 'hard'....

I put a Warp9, zilla 1k, 160v CALB LiFePO in my eMiata, and generally start in 3rd, or sometimes just leave it in 4th if I'm tooling around the city. Occasional burnouts in 2nd to show off, but hardly ever start in 1st because it seemed like a waste of time with all that torque available.

I drove like this for a couple years, and decided to upgrade my clutch, lighten the flywheel and remove starter ring as I could feel a little clutch slip on hard starts and I wanted to upgrade a little. I was super happy with the performance afterward..... BUT after about a year of NOT slipping on hard starts, the torque basically peeled all the teeth off third gear one day!

so....... beware of hard starts, especially not in 1st gear, through a transmission not designed to handle the torque!

my plan for the future is to replace the rear diff with much taller gears, probably from a newish Mustang so I can basically use the entire rear independant suspension and differential sub-system, and get a 2.73 or 3.11 or 3.15 rear end..... which would have the double advantage of making 1st gear useful and give me a better top end as I have been rpm limited with stock to about 90 mph or so at 4500 rpm
 

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Wow, sorry for your loss, but that is really cool.

What an awesome machine you built. Do you think this was metal fatigue over time or just one big over-torque event that shucked those teeth?

Thanks for sharing.
 

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Discussion Starter #3
Wow, sorry for your loss, but that is really cool.

What an awesome machine you built. Do you think this was metal fatigue over time or just one big over-torque event that shucked those teeth?

Thanks for sharing.

I 'typically' started in 3rd gear.... and I KNOW I was putting about 2x the design torque thru the transmission, and was counting on typical design safety factors to carry me though.

What I didn't really think about until after the fact is that the transmission was DEFINITELY NOT designed for hard starts in any gear other than first, and not exactly designed for drag racing dropping the clutch and burnouts 'shock loads' in any gear.

typically a manual, especially a small underpowered car like a Miata, is not really expected to take sudden torque between gears, or even from a stop really as that is what the clutch is for, right?! ;)

so, fun as it is, burnouts and hard starts are NOT a great idea unless you have beefed up the transmission accordingly. that's really why I posted this; as followup to the tendency for us DIY conversions to be thrilled with doubling the torque from whatever we converted......
 

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my plan for the future is to replace the rear diff with much taller gears, probably from a newish Mustang so I can basically use the entire rear independant suspension and differential sub-system, and get a 2.73 or 3.11 or 3.15 rear end..... which would have the double advantage of making 1st gear useful and give me a better top end as I have been rpm limited with stock to about 90 mph or so at 4500 rpm

Will you also be using the Mustang transmission so that the gearbox has a fighting chance?
 

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I have a similar car, same electronics 1k zilla, warp 9, 16 12v agm, but no trans. I calculated the power at 350hp, 500# tq. So of course you ripped up the transmission. A mustang rear will help but you need a better tranny. I was thinking about a glide with a pump and that would do it, built one best.
 

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Something you can do to help a little is, when hard launching from dead stop try pre-loading the gears first. Basically hold the brake and apply some throttle so the car wants to inch forward but the brakes hold it. This will mesh the gears in forward position so that once you let go of the brake, the gears “push” instead of “slap” each other .

This is one of the techniques we Mitsubishi Evolution owners (and probably many other awd platform cars) do to reduce risk of damage to the transfercase or transmission when launching the car.
 

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Discussion Starter #8
Will you also be using the Mustang transmission so that the gearbox has a fighting chance?
well.... I JUST spent money to replace with a rebuilt Miata tranny, and have upgraded the clutch and flywheel.... so no, I probably would do just the rear diff and see how that holds up.
 

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Discussion Starter #9
I have a similar car, same electronics 1k zilla, warp 9, 16 12v agm, but no trans. I calculated the power at 350hp, 500# tq. So of course you ripped up the transmission. A mustang rear will help but you need a better tranny. I was thinking about a glide with a pump and that would do it, built one best.
yes, if I were going to do another car with this amount of power, or more, I would certainly consider a 'locked' powerglide or a T5 or something like that.
 

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Discussion Starter #11
What does the adapter plate/coupling set-up look like?
the flat plate adaptor I think was from CanEV. it retains the clutch/flywheel. nice motor mount custom welded to hold motor with stock motor mounts.

http://envirokarma.org/ev2_mx5e/gallery/120927_motor_mount.htm

About two years or so ago I ditched the stock clutch and flywheel and went with a stage 2 clutch, aluminum flywheel, and removed the starter ring. I did all this when the original '94 tranny started making bad noises. I replaced the '94 tranny with a '98 as they were designed to carry a little more torque.... but obviously, not quite enough....

which is why I started this thread.

To document that IF you are going to drive hard, and have a 144v+, 1000amp controller running thru a Warp9, you would be well advised to have a tranny rated for 300+ft-# of torque.
 

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yes, everything well centered and well balanced.
If the set-up aligns the motor output shaft rotational axis and the transmission input shaft normal rotational axis within 0.005" (~0.13mm), as most OEMs require(almost always done with alignment dowels); and the input shaft is well located and supported with a pilot bushing or spacer, it looks like a transmission with a higher torque rating is required.
 

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What a fantastic bit of autopsy, thanks for sharing!

I'm leaning more and more towards just direct drive on my build.

'Course, I still have to worry about the torque spat at the final drive, but, hopefully it's more robust than high gear starts.
 

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Discussion Starter #16 (Edited)
What a fantastic bit of autopsy, thanks for sharing!

I'm leaning more and more towards just direct drive on my build.

'Course, I still have to worry about the torque spat at the final drive, but, hopefully it's more robust than high gear starts.
direct drive with DC really doesn't end up working very well in the builds I've followed in the past. You end up sacrificing on one end or the other because DC motor rpm is limited to about 6000rpm for the 8", and 5000 for a 9", and probably 4000 for an 11". You'll have sluggish acceleration OR limited top end.

direct drive with AC motor might work with an AC-31 or AC-51, but you'll spend a LOT more on the motor/inverter than you would with DC.
 

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. You'll have sluggish acceleration AND limited top end.

.
Funny that

I beat ALL of the supercharged V8's with my Device - and got "fined" for it!

7.90 seconds and 93 mph (for the 1/8th)

That's 150 kph and 5300 rpm - the motor expert (Major) thinks I should be OK to 6500 rpm with my Hitachi
That would be 114 mph and 180 kph

I think that a top end of over 100 mph and decent acceleration is not

"sluggish acceleration AND limited top end"

Especially as the speed limit here is 100 kph
 

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Discussion Starter #18
Funny that

I beat ALL of the supercharged V8's with my Device - and got "fined" for it!

7.90 seconds and 93 mph (for the 1/8th)

That's 150 kph and 5300 rpm - the motor expert (Major) thinks I should be OK to 6500 rpm with my Hitachi
That would be 114 mph and 180 kph

I think that a top end of over 100 mph and decent acceleration is not

"sluggish acceleration AND limited top end"

Especially as the speed limit here is 100 kph
Duncan..... what is the weight of your vehicle? How about the range? Does it have enough batteries for 40-60 mile daily drive?

I am talking about the 'average' conversion of a street legal compact car that can be used as a daily driver. putting out 100 to 150 kw with a single 8" or 9" brushed DC motor in a single speed vehicle weighing 2600-2800# will NOT get you these performance numbers without gears.

I did not start the thread to start a holy war.... just to note what happens when you push 250ft-# of torque thru a tranny designed for 150 and start in 3rd gear most of the time.
 

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Hi
Road legal - check
Range - 50 km - enough for 90% of journeys

Back when I was using a 144v pack and a 500 amp controller - 70 Kw it was still a spritely little car with more than enough to blast past the speed limit

When I dropped to 130v - Then it was a bit slow at the top end - 100 kph

Today I have a control switch - and I set it to 45% - so for normal driving I'm limited to 540 amps (100% is 1200 amps)
full power on std road tyres is simply TOO exciting

It's FAST and FUN at 45%

If somebody is building a FWD THEN using the gearbox is a good idea

If they are using the conventional front engine RWD then a gearbox simply gets in the way

I have a lot more rear grip than most cars and with 500 amps and road tyres I can spin the rear tyres

When I was doing the numbers I found that the gearbox was simply unnecessary - the difficult thing with any of these conversions - is finding somewhere to put the batteries so with the motor where the gearbox would live you have the whole engine bay for batteries

So my device with 75 Kw and direct drive is great fun
I would expect a Spitfire, Miata, or any small RWD car to be fun with the same power

A 100 kw or 150 kw motor controller would be great fun

On the track or the strip with 1200 amps and 340 volts and sticky tires.....
 

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Discussion Starter #20
Hi
Road legal - check
Range - 50 km - enough for 90% of journeys
range of 50km is probably not quite enough for the US market, especially in the southwest with generally longer commutes between home-work. Our market targets 50 miles as the threshold for 90% of trips, especially in 2-car households.

I still am wondering what the weight is of your vehicle....
I know that my eMiata gross weight is 2360#
With the stock rear differential, I know that if I start in 2nd I have to be careful of wheel spin,
if I start in third its right at the edge of traction
if I start in 4th, which is 1:1, acceleration is significantly slower and motor rpm limited to 4500 rpm (for a Warp9) restricts my top end to 80 mph or so

this is the basis for my statement that while direct drive is certainly possible, you will compromise at one end or the other versus what you can get with a transmission.

It also leads me to my next 'tweak', which is to retain my newly rebuilt transmission, and see if I can get taller gears in the rear diff such that starting in 1st gear will be 'useful', and cruising at my local highway speed limit of 75mph is at a comfortable rpm with normal traffic moving at closer to 80-85mph.

The last consideration I had when deciding to retain a transmission is that it seemed much better to have a reverse gear rather than depend on reversing contactors and the extra high-voltage cabling to run the DC motor backward, especially since the Warp9 is 'advanced' to optimize performance in the forward direction.
 
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