transmission less conversion

A couple of other ideas (recognizing this is a '54 Ford):

1) Mount the motor on the rear carrier, no driveshaft or slip joint, still need a coupler if you don't use a chain or belt drive, or

2) Put an IRS in the back (many hotrodders, nowadays, known as "restomodders", do anyway, which again eliminates the slip joint, needs a coupler and an arbitrarily long driveshaft. Unlike the old days where Corvette and Jag were the only readily available choices, there are a few more out there for IRS these days.

One other issue you need to think about with your industrial motor (seems to be a secret of what it is with the way you took the pics, so I have to guess that's what it might be given the keyed shaft) is cooling.

Most stationary motors have an integral fan on the rotor, which is completely useless at low RPM, and that's where most people dump the highest current into a traction motor. You can get some motors that have a separately motored fan from things like machine tools (not cheap).

Maybe you have that taken care of, but getting gobs of air down a trans tunnel that's plugged by a motor is a tough nut to crack as well. Especially fun when you have a block of batteries blocking airflow to the tunnel.

You also are starting out with a heavy car. Coupling it to the rear end by whatever means only gives you a 3:1 to 5:1 torque increase. If you're using a 3600 RPM motor, you don't have much choice but to couple to the rear end if you want to have a chance at hitting highway speeds, If it fits in a tunnel, with direct drive acceleration could be sucky, though.

I'm sure you've done the math on wheel speed. Less likely you did the math for acceleration. Putting the motor anywhere, including the engine bay, needs thinking about cooling and not merely about how to attach the rotor to a prop shaft.

As I said, maybe you've thought about all this, but if you (or future project folks) haven't, you may be in for a nasty & expensive surprise.

For a 54 Ford (say a Customliner sedan) you do need 2x something.

In this case, I think you can make it work with 1 motor and a 2x gear reduction. The gear reduction will halve your rpm (so now the 6000 rpm from the motor fit the 3000-rpm drive train design) and it will double your torque. That should get the total weight off the line with normal-people performance.

If you want white-zombie-speeds etc then yes, the whole car needs to be reinforced etc.

I'm doing a 1959 Cadillac sedan, and it's with 2 motors and a 2x reduction. A Karman Ghia is 1800 lbs and uses 1 motor & no gear because the drive train needs 4000-6000 rpm, the Ford Customliner at 3500 lbs would use 1 motor and a 2x reduction, and the Cadillac is 5600 lbs with 2 motors and a 2x reduction.

There's a weird logic in those numbers but I think it all works out....

Duncan said:

You only want the reduction gear if you are using a wimpy AC motor

A DC motor is a LOT cheaper
Does not need the reduction gear...

Click to expand...

Yeah, Tesla's motors must be really wimpy, since they seem to need that 12:1 ratio two-stage reduction.

You can productively use a greater reduction ratio than existing in the final drive if your motor can turn more than a few thousand rpm. If you're using century-old technology with brushes that don't let the motor turn as fast as an economy car's engine, then you use a really big motor at low speed, and the stock final drive ratio works well.

In looking at alternatives for my Spitfire, I concluded that if I were to convert it, I would want to keep the existing final drive and to eliminate any other transmission (so it would be configured like the plan for this project). I have considered the Chevrolet Spark EV motor, because it was designed to be used with only one stage of reduction gearing... and while it is built with the same technology as the Chevrolet Bolt motor, the slower Spark EV motor is substantially bigger and heavier while capable of producing less power. That's the price of slow motor operation, but if your type of motor can only turn slowly, then maybe that's not a problem.

Frankenfiftyfour said:

Here's an idea I was thinking about. I still have the output housing and shaft from the transmission. If I could modify it to mount to the electric motor and it would solve a lot of problems. Here's the issue with that:

The original set up fed ATF to keep the output shaft for lubrication.

What if I tapped the housing for grease fittings to pump grease into the areas in question? Would this even work?

Click to expand...

What you are talking about doing is essentially duplicating NetGain's TransWarP motors, which are the same as their WarP motors (which are generic brushed series DC motors like those from an old forklift), but with a splined shaft end and added tailshaft housing. For lubrication, they only add grease fittings for the slip joint... but the output spline is on the motor shaft, so they're not adding or needing to support an extra shaft section, and larger sizes (9" and 11") have upgraded output-end bearings to handle the radial load.

If you must use a common motor without a splined output compatible with a sliding yoke for the propeller shaft, and your motor speed doesn't call for additional reduction gearing, a simple U-joint yoke and a propeller shaft with a sliding section (as Duncan suggested) is certainly the straightforward solution.

Duncan said:

You only want the reduction gear if you are using a wimpy AC motor

A DC motor is a LOT cheaper
Does not need the reduction gear
And you probably don't need two

But it is a little less "sophisticated"

Click to expand...

AC or DC is hardly the point. Also, I just looked and a 70 bhp AC motor is $2,900 and a 58 bhp DC motor (warp 11) is $3,200. Close enough that no-one is a LOT cheaper.

My point/question (because of the type of the cars) was about total bhp and total torque. I'll happily take any advice I can get, I'm not interested in measuring wimpiness or sophistication. This is an engineering puzzle so let's stick to the numbers.

I'm trying to match driving behavior. Like accelerating from 65 to 80 mph to over-take Elmer Fudd in his pick-up truck. For that, things should be close to original (I think).

The original engine had 430 ft lbs of torque and 325 bhp @ 51% rating (at 4,000 rpm). Alright, so be it, and those are the numbers I need to match to get to comparable performance.

One DC Warp 11 is ~55kW, so two of them is 110 kW / 0.7 = 160 bhp. The original had 51% of 325 = 170 bhp at the drive shaft, so I'm pretty close (within 10%).

One DC Warp 11 has 140 ft lbs. I need 430, so 3x what one Warp 11 can do. So, take 2 Warp 11's and a helical gear = 2 x 140 x 1.7 = 475 ft lbs. Again, a little better, but not a lot (10%).

Sure, I should get all my torque at 0 rpm / start-up and all that, but I'm building a road-car, not a drag racer. To me the numbers say 2 motors and a gear. If there's a hole in these numbers then let's discuss. What am I missing in this?

Yes, I went with AC because of what I had available, and my motors actually get about 100 bhp and 200+ ft lbs each so I should have a zippier car than what it was originally. Then again, the original was hardly a street racer plus this is the US so it's not going to help with speed-limits of 65 and 70 mph ...

Hi Rob kr

I paid $100(NZ) form my first Hitachi 11 inch motor

The latest one I bought (as a spare) cost me $200

THAT is the cost of DC motors - and I'm pushing 1200 amps and 340 volts - 500 hp

You are comparing that to a limp wristed 70 hp at 15 times the cost!

AND the AC motor will need a controller that is a lot more expensive than a P&S

Modern OEM AC motors are GREAT

Aftermarket AC motors are wimpy and expensive