[brian_]

Back in '75 turbo hydro trannies were weak. That may have changed as shown in the racing catalogs.

There have been many Turbo Hydramatic transmissions, but the reliability disaster of that era was the THM 200. Fortunately, that's not what Blake has.

 

[brian_]

Transmissions basically go downwards - they make the motor spin faster!

In most (not sure about autos) of the old gearboxes top gear was 1:1 - straight through

Yes, most transmission ratios are reduction gears (output lower than input). Modern transmissions typically have one or more overdrive gears (output faster than input), but a THM 350 (and any Turbo Hydramatic before the the 4-speeds of the early 1980's) has a 1:1 top gear. In these traditional automatics, in this direct gear the power isn't going through any gears at all, but lots of gears used for other ratios are still spinning.

Which is what you get if you throw away the trans and go direct drive!

Yes, but keeping the transmission allows higher motor speed and thus more torque to the wheels at low road speeds. If that reduction gearing is not needed, I agree that a transmission is pointless.

 

[brian_]

Also do you think that if this motor is coupled to the trans I will be able to use the trans ability to shift gears to keep motor rpm around 2500 rpm while achieving highway speeds? I’d like to use the trans so I can have a higher top speed and reverse.

Cars back then came with a lot of configuration options, and anything could have been done in the past four decades, but the stock tire was something like an FR78-14, which was about the size of a P205/75R14, which is about 26.5" tall and so turns about 800 revolutions per mile. That means at 60 mph the tire and wheel are turning at 800 rpm. although you probably want and have something wider and lower profile than this, such as a 235/60R15, as long as the overall diameter is the same the gearing situation is the same.

A typical final drive ratio for a 350 V8 1975 Nova would be 2.73:1, although apparently there were optional 2.56:1 and 3.08:1 ratios (according to the GM info kit), and again the axle currently in the car could be just about anything. With a 2.73:1 ring and pinion, the propeller shaft (driveshaft) speed with 800 rpm wheel speed would be about 2200 rpm.

You don't need any gearing other than the final drive (so, you don't need a transmission) to get a reasonable motor rotational speed at highway road speed, if you're looking for 2500 rpm at some highway speed.

Reverse is another issue entirely...

 

[brian_]

...
My diff is 4.1:1 - yours is 2.5:1 - so I have 60% more torque

BUT you have a larger motor so you will get more torque per amp

I suspect that with 1200 Amps and direct drive you will be able to spin your rear tyres - unless you buy super sticky tyres

I normally drive mine with the 1200 amps reduced to 550 Amps - 1200 amps is just a bit too exciting on the road

Major thinks that I can get to 6000 rpm before my motor explodes - 50% higher than yours
So if you have a 2.5:1 diff which is 64% higher than my 4.1:1 - it about cancels out!

My top speed (before motor blowup) will be about 100 mph - so you should be about the same - bit higher

All good, except that the cars likely use different tires sizes as well, changing the relationship of motor speed to road speed, and of motor torque to accelerating force.
Note: torque = force * distance, so accelerating force = torque / tire rolling radius

I guessed the Nova as having about 26.5" (673 mm) tall tires.
Duncan, what's on the Device?
Blake, what are your actual tire size and final drive ratio?

 

[brian_]

So you have HUGE torque but SLOW RPMs with that 13" motor beast, you need a gear AMPLIFIER, as opposed to a gear reductor like the built-in gear reductor every VW Acapulco or "Safari" has, (as we know it here in Mexico), I haven't seen your EV specs but certainly if there is a transmission, you have to skip 1st and 2nd gear from 0 RPM all the time, you need to start in 3rd gear.

The motor in Duncan's Device drives the input of the final drive (differential) without additional gearing; it runs as if it had a traditional transmission and was always in the direct (1:1) gear.

I find it strange, at the very least, to declare another builder's design to be faulty without even knowing what the design is.

Also, overdrive or step-up gearing is not an "amplifier", any more than reduction gearing is an attenuator.

Why AMD stopped their DC Series Motor production remains a mystery to me, I assume they followed the absurd argument of the Automotive Industry "DC Series Wound motors are obsolete because they are less than 90% efficient, they do not offer regen and they need maintenance" so everyone is moving to AC or PM rare earth reluctant motors for twice or trice the cost... to get 8% more efficiency? Absurd!

If you don't understand that doubling the cost of one component is well worth the expense for substantially greater efficiency and avoiding maintenance (and failures), then you don't understand the automotive industry at all.

So far, in EvAlbum AMD/Advanced DC Motor is "the most popular motor used for conversions." It's Not the HPEVS AC50, not the Warp 9, it is the AMD/Advanced DC 9" motor.

It shouldn't be surprising that a historical collection of do-it-yourself projects by people who can't afford current technology is dominated by old forklift truck motors, many with a new label on them , or that people assembling vehicles with extremely limited development resources have most often chosen the simplest design.

And THE most popular controller (because I believe it was the first is the OLD and OBSOLETE CURTIS), Curtis is using the same old technology since the 90's (perhaps the 80s, not sure)...

Now that's bizarre: dismissing modern motor technology as absurd (in favour of motor design from over a century ago), but attacking a newer controller technology as old and obsolete.