DIY Electric Car Forums banner
1 - 20 of 29 Posts

·
Registered
1968 Oldsmobile 442
Joined
·
7 Posts
Discussion Starter · #1 ·
Hello,

I have been playing with the idea of modifying my 1968 Olds 442 from a gas enginer to an electric motor(s) setup. I have looked at elaphe in wheel motors but they don't seem to want to sell to consumers. I am trying to determine if it would be worth doing this. I know if have weight issues with the car but I don't know where to start to even determine the feasibility of doing this.

Any thoughts/comments welcome.

chris
 

·
Registered
Joined
·
7,970 Posts
Welcome to the forum, Chris.

I have looked at elaphe in wheel motors but they don't seem to want to sell to consumers.
Lucky for you, because it saves you from dealing with that nonsense :)
In-wheel motors are good for some low-speed equipment and heavy vehicles, but are lousy for cars that need to ride and handle well... which is why they are not used. Elaphe has probably made a lot of prototypes for demonstration, and produces units for some applications, but probably doesn't actually have a production item for cars, since no automotive manufacturer has ever purchased them.
 

·
Registered
1968 Oldsmobile 442
Joined
·
7 Posts
Discussion Starter · #3 ·
Welcome to the forum, Chris.


Lucky for you, because it saves you from dealing with that nonsense :)
In-wheel motors are good for some low-speed equipment and heavy vehicles, but are lousy for cars that need to ride and handle well... which is why they are not used. Elaphe has probably made a lot of prototypes for demonstration, and produces units for some applications, but probably doesn't actually have a production item for cars, since no automotive manufacturer has ever purchased them.
Thanks for the welcome. Yes they are problematic. Their solution looks good from an aesthetics and form factor point of view. What are better options?
 

·
Registered
Joined
·
26 Posts
If you tell me what specs you're looking at, I'd be more than happy to cook up a little calculator for you. I currently have very nice torque curves for the AMR racing motors, but they're a bit pricy, so I could have a look for other stuff.
Some good specs to start with:
Budget
Desired top speed
Desired mileage
Desired 0-60

I like the idea of having individual motors for each wheel, but in-wheel hub really isn't the best way to do that: it means that your motors have to be loadbearing, and doesn't offer any real rewards. A good alternative solution is just doing it the "normal" way: most cars have bearings with half-shafts attached that are used to drive the motors. The other end is attached to the differential, so if you buy some shorter half-shafts, you can still have one motor driving each wheel and avoid the unsprung weight issue. Alternatively, you could just hook up the electric motor to the stock differential, preferably with some reduction in between that.
 

·
Registered
Joined
·
7,970 Posts
Their solution looks good from an aesthetics and form factor point of view. What are better options?
Aesthetically, motors are not seen from the outside, so I don't see how it matters... maybe I'm missing something. Packaging (form factor) is definitely the big selling point for in-wheel motors, and without resorting to them you're just stuck with drive units (motors with gearboxes) at each axle or for each wheel... like all production EVs use.
 

·
Registered
1968 Oldsmobile 442
Joined
·
7 Posts
Discussion Starter · #6 ·
Aesthetically, motors are not seen from the outside, so I don't see how it matters... maybe I'm missing something. Packaging (form factor) is definitely the big selling point for in-wheel motors, and without resorting to them you're just stuck with drive units (motors with gearboxes) at each axle or for each wheel... like all production EVs use.
I guess I was going for the simplicity of the design. With the electric motors on each wheel one can remove the drive shaft, engine, tranny and save a lot of weight. You'll need it for those batteries.
 

·
Registered
1968 Oldsmobile 442
Joined
·
7 Posts
Discussion Starter · #7 ·
If you tell me what specs you're looking at, I'd be more than happy to cook up a little calculator for you. I currently have very nice torque curves for the AMR racing motors, but they're a bit pricy, so I could have a look for other stuff.
Some good specs to start with:
Budget
Desired top speed
Desired mileage
Desired 0-60
Budget, well that is the million dollar question. Since I have no real idea of how much or how little it will cost I cannot offer a number, yet.
Top speed, I would shoot for what stock did for my car
Desired mileage, better than stock for sure! 200 miles is about what I get now.
Desired 0-60, I would like that to be improved from what it was back in the day. I don't recall what it was but if we are in the 4's that would be good.

I like the idea of having individual motors for each wheel, but in-wheel hub really isn't the best way to do that: it means that your motors have to be loadbearing, and doesn't offer any real rewards. A good alternative solution is just doing it the "normal" way: most cars have bearings with half-shafts attached that are used to drive the motors. The other end is attached to the differential, so if you buy some shorter half-shafts, you can still have one motor driving each wheel and avoid the unsprung weight issue. Alternatively, you could just hook up the electric motor to the stock differential, preferably with some reduction in between that.
I have a the typical GM rear end with a differential. And motor up front that can turn the drive shaft might be ok. I'd have to replace that drive shaft and go with a lighter aluminum one I think.

Chris
 

·
Registered
Joined
·
26 Posts
Alright. That's a top speed of 115 mph, better than 4 second 0-60, better than 200 mile range.
This is your calculator, based on 2 AMR racing 250-90 motors, one to a wheel in the back. Your top speed with a 7.3:1 gear reduction is about 113 miles per hour, your zero to 60 is 3.1 seconds, and your 0-100 is 5.4 seconds.

This is a highly unoptimistic assumption of distance: I just multiplied power consumption at 60 mph by 1.5 to account for accel/deaccel, braking, ac, controllers, etc. This also doesn't account for regenerative braking, so keep in mind that your mileage will vary. That said, you should be able to travel 250 miles at 60 mph on 90 kwh of batteries. Once again, I'm probably seriously underestimating that.
 

·
Registered
Joined
·
7,970 Posts
I guess I was going for the simplicity of the design. With the electric motors on each wheel one can remove the drive shaft, engine, tranny and save a lot of weight. You'll need it for those batteries.
Of course any EV doesn't have an engine, so that's not part of the in-wheel pros and cons discussion.

Whether the motor is on the wheel or mounted to the structure of the car, you have a choice of large and heavy motor driving at wheel speed, or smaller and lighter motor at higher speed and a reduction gearbox (transmission). An in-wheel design forces the transmission (if used) to fit in the wheel with the motor (and hub with bearings, and brake).

Many conversions have the motor mounted where the engine or transmission was and a long propeller shaft (driveshaft), but there's no need to go right to putting the motor in the wheel. All production EVs out the motor(s) at the axle location, driving through a gearbox; the only shafts external to the transmission(s) are the axle shafts.

In-wheel motors would avoid the jointed axle shafts, but require longer power cables and coolant lines (or limit the motors to air cooling.
 

·
Registered
Joined
·
7,970 Posts
I have a the typical GM rear end with a differential. And motor up front that can turn the drive shaft might be ok.
"Typical GM rear end" in this case means a live beam axle, which was typical when this 4-4-2 was built. Almost nothing, even from GM, uses that any more other than trucks.

There are two fundamental approaches, based on suspension:
  • keep the beam axle, or
  • replace it with independent suspension.
Essentially every production rear-wheel-drive or AWD car has an independent rear suspension, so essentially every production electric car uses independent rear suspension. The powertrain is then obvious: one motor with a transaxle (transmission and differential), or in some cases two motors each with their own transmission. There's no question that this makes the best car, but I don't see any sense in doing this with a classic 4-4-2 unless you're really attached to the body style and don't car about preserving any of the car's character mechanically.

If the beam axle is retained then there are three choices:
  • mount the motor (and likely gearbox) in place of the original engine and transmission
    • this is the traditional EV conversion approach
    • it requires the fewest new components (the entire rear axle and suspension remain unchanged), but takes more space in the car than any other design
    • unless the motor is very large it won't have enough torque to work with just the reduction gearing in the axle so an additional transmission is needed (the car's original transmission can work, but is very bulky and heavy)
    • the shaft from gearbox (or directly from motor) to axle can be shorter than stock if the motor/gearbox can be mounted back than the original (which was determined by the engine)
  • mount the motor (or motors) on the axle
    • this is done for some industrial vehicles, trucks, and buses
    • the unsprung weight (carried on the axle) is very high, so ride quality and handling are poor
    • this is like the in-wheel solution, except that everything doesn't need to be jammed into the wheel space
  • use a de Dion axle
    • this fixes the unsprung weight problem, but requires a completely different axle and jointed half-shafts
    • it is essentially the beam axle suspension, but with a final drive (diff) mounted to the frame and connected to the hubs with jointed axle shafts like those used with an independent rear suspension
The originally discussed in-wheel motors and the "motor up front that can turn the drive shaft" are completely opposite ends of the range of possibilities.

I'd have to replace that drive shaft and go with a lighter aluminum one I think.
Whatever design is used, the weight of that drive shaft is not important.
 

·
Registered
1968 Oldsmobile 442
Joined
·
7 Posts
Discussion Starter · #11 ·
Alright. That's a top speed of 115 mph, better than 4 second 0-60, better than 200 mile range.
This is your calculator, based on 2 AMR racing 250-90 motors, one to a wheel in the back.
Is it right that they are about $10K per motor?

Your top speed with a 7.3:1 gear reduction is about 113 miles per hour, your zero to 60 is 3.1 seconds, and your 0-100 is 5.4 seconds.
How does one achieve that kind of gear rededuction? My diff is a 3.08.

This is a highly unoptimistic assumption of distance: I just multiplied power consumption at 60 mph by 1.5 to account for accel/deaccel, braking, ac, controllers, etc. This also doesn't account for regenerative braking, so keep in mind that your mileage will vary. That said, you should be able to travel 250 miles at 60 mph on 90 kwh of batteries. Once again, I'm probably seriously underestimating that.
Unrealistic to drive at 60 mph on an Arizona freeway. 75 mph is the going speed.

Chris
 

·
Registered
Joined
·
61 Posts
You can probably get similar specs from a performance large Tesla motor.
$9k gets you 440ftlbs and 530hp

you’re gonna need probably $15k worth of batteries to get that kinda range though
 

·
Registered
1968 Oldsmobile 442
Joined
·
7 Posts
Discussion Starter · #13 ·
You can probably get similar specs from a performance large Tesla motor.
$9k gets you 440ftlbs and 530hp

you’re gonna need probably $15k worth of batteries to get that kinda range though
What about the electronics involved to operate the motor and battery pack? $24K off the top is a lot and not complete is a lot to fork out. Maybe I am oblivious to the actual cost of doing the conversion?

chris
 

·
Registered
Joined
·
26 Posts
For electronics, it partially depends on where you shop.
I'll do StealthEV because I have it up right now:
16 5.6 kwh battery modules: 25600
15 battery jumpers: 750
Tesla Gen2 Charger: 2000
Battery Management systems: I don't know which you would need, but I have a feeling it would be between 1800 and 1900 dollars.
DC DC converter: 1500 dollars, or you could package it with a charger to get slightly lower charge rates but lower cost for 2699
Aftermarket dispay: 750
Tesla Drive Unit $9,000 for performance, $12,000 for ludicrous.
Plus $2500 for unforeseen expenses, connecters, etc.
Total price of about 43990 for the full conversion, rounded up to $44000. You'd also need a charging station.

As for motors: I only used the AMR motors because I happened to have the curves, and because I'm using them for a situation where I can't use the Tesla motors. Your specs are well suited to the Tesla motors, use those instead. For gearing with those, I would recommend asking someone who has worked with them before.

As for range: The Oldsmobile is not one of the sleekest cars on the market. At a cruising speed of 110 mph, the motor would draw 81 kw, no matter what gearing or motors you use. That's how much the motor consumes to overcome air and rolling resistance. If it had the coefficient of friction of a tesla, you would only consume 33 kw at that speed. If I were you, I would look at regenerative braking and other methods for recovering as much energy as possible: you'll need every last drop.
 

·
Registered
1968 Oldsmobile 442
Joined
·
7 Posts
Discussion Starter · #15 ·
For electronics, it partially depends on where you shop.
I'll do StealthEV because I have it up right now:
16 5.6 kwh battery modules: 25600
15 battery jumpers: 750
Tesla Gen2 Charger: 2000
Battery Management systems: I don't know which you would need, but I have a feeling it would be between 1800 and 1900 dollars.
DC DC converter: 1500 dollars, or you could package it with a charger to get slightly lower charge rates but lower cost for 2699
Aftermarket dispay: 750
Tesla Drive Unit $9,000 for performance, $12,000 for ludicrous.
Plus $2500 for unforeseen expenses, connecters, etc.
Total price of about 43990 for the full conversion, rounded up to $44000. You'd also need a charging station.

As for motors: I only used the AMR motors because I happened to have the curves, and because I'm using them for a situation where I can't use the Tesla motors. Your specs are well suited to the Tesla motors, use those instead. For gearing with those, I would recommend asking someone who has worked with them before.

As for range: The Oldsmobile is not one of the sleekest cars on the market. At a cruising speed of 110 mph, the motor would draw 81 kw, no matter what gearing or motors you use. That's how much the motor consumes to overcome air and rolling resistance. If it had the coefficient of friction of a tesla, you would only consume 33 kw at that speed. If I were you, I would look at regenerative braking and other methods for recovering as much energy as possible: you'll need every last drop.
Thanks for elaborating all these details! I guess I will have to just go with a rebuild of the motor and use gasoline and maybe incorporate a GV unit. Far cheaper than 40K+!
 

·
Registered
Joined
·
61 Posts
Batteries are the most significant part of a conversion and their price can vary substantially depending on your project goals and needs. Do you really need 200 miles of range or can you get buy with 100, for example? How much hunting are you willing to do to score a deal? You could probably find two Chevy Volt packs for far less than $25k (more like $6-10k) which would get you to the the right voltage range and around 35kWh. The biggest downside of Volt batteries is they are pretty bulky, but you're talking about a large car with a lot of space so it shouldn't be an issue. There are people who have wedged two Volt packs into far smaller cars, like a 1981 Honda Accord or a BMW E30.

But yes, bottom line is conversions aren't cheap and for any performance benchmark you can almost certainly meet it with ICE for less money at this point.
 

·
Registered
Joined
·
7,970 Posts
How does one achieve that kind of gear rededuction? My diff is a 3.08.
Production EVs use a two-stage gear reduction system in a transaxle... it's just like the transaxle used with a transverse engine, but with only the gears for one ratio (like it was in 2nd gear and all the other gears were removed).

If you use the car's original axle with differential and ring-and-pinion gears, the only way to get the desired reduction ratio is to use an additional gearbox (usually mounted on the output of the motor), as I noted earlier:
If the beam axle is retained then there are three choices:​

  • mount the motor (and likely gearbox) in place of the original engine and transmission
    • this is the traditional EV conversion approach
      • it requires the fewest new components (the entire rear axle and suspension remain unchanged), but takes more space in the car than any other design
      • unless the motor is very large it won't have enough torque to work with just the reduction gearing in the axle so an additional transmission is needed (the car's original transmission can work, but is very bulky and heavy)
      • the shaft from gearbox (or directly from motor) to axle can be shorter than stock if the motor/gearbox can be mounted back than the original (which was determined by the engine)
    • ...

A gearbox built specifically for this purpose is the ev-TorqueBox from Torque Trends.

A compromise is to get the most extreme ratio ring and pinion for your axle, and settle for whatever ratio that might be. With some axles, it can be greater than 6:1, even though regular production ratios are in the range of about 3:1 to 4:1.
 

·
Registered
Joined
·
7,970 Posts
You can probably get similar specs from a performance large Tesla motor.
$9k gets you 440ftlbs and 530hp
Yes, the Tesla Model S large drive units is a popular choice for DIY conversions because it offers the most power (in brief bursts) of any reasonably available solution which doesn't require building electronics.

Unfortunately, there is no easy way to use this in a car with live beam axle. The motor doesn't reasonably split from the transaxle, and with the transaxle it can only be used in an independent or de Dion rear suspension:
There are two fundamental approaches, based on suspension:​
  • keep the beam axle, or
    • replace it with independent suspension.
Essentially every production rear-wheel-drive or AWD car has an independent rear suspension, so essentially every production electric car uses independent rear suspension. The powertrain is then obvious: one motor with a transaxle (transmission and differential), or in some cases two motors each with their own transmission. There's no question that this makes the best car, but I don't see any sense in doing this with a classic 4-4-2 unless you're really attached to the body style and don't car about preserving any of the car's character mechanically.​
If the beam axle is retained then there are three choices:​
  • ...
  • use a de Dion axle
    • this fixes the unsprung weight problem, but requires a completely different axle and jointed half-shafts
      • it is essentially the beam axle suspension, but with a final drive (diff) mounted to the frame and connected to the hubs with jointed axle shafts like those used with an independent rear suspensio

One way to use this drive unit in this sort of car is to also use the whole rear suspension and subframe, completely replacing the 4-4-2's original axle and rear suspension (as well of course replacing the engine and transmission).
 

·
Registered
Joined
·
7,970 Posts
What about the electronics involved to operate the motor and battery pack? $24K off the top is a lot and not complete is a lot to fork out. Maybe I am oblivious to the actual cost of doing the conversion?
Yes, most people are wildly unrealistic about the cost of the conversion they want when they first start discussing it. Of course a less expensive conversion is possible, but not with high performance (acceleration, top speed, or range).
 

·
Administrator
Joined
·
6,443 Posts
Batteries are the most significant part of a conversion and their price can vary substantially depending on your project goals and needs. Do you really need 200 miles of range or can you get buy with 100, for example? How much hunting are you willing to do to score a deal? You could probably find two Chevy Volt packs for far less than $25k (more like $6-10k) which would get you to the the right voltage range and around 35kWh. The biggest downside of Volt batteries is they are pretty bulky, but you're talking about a large car with a lot of space so it shouldn't be an issue. There are people who have wedged two Volt packs into far smaller cars, like a 1981 Honda Accord or a BMW E30.

But yes, bottom line is conversions aren't cheap and for any performance benchmark you can almost certainly meet it with ICE for less money at this point.
Disagree with the last point - you can easily destroy a petrol car costing much much more for PERFORMANCE

The issue as you have identified is the RANGE - if you want 200 miles its going to be expensive and the extra weight of the larger battery pack will hurt your performance

We see this in competition - something like the Pikes Peak Hillclimb is owned by the electric cars - because its short range

Have a very close look at what you actually do
When I looked at my driving patterns I found that I was either doing less than 50 km - or well over 150 km
I have a "50 km" battery in my car - it is about 130 kg (14 kwh)
If I had wanted the next level I would have had to add at least another 260 kg - which would have taken my 800 kg car to 1060 kg

Volt batteries - I LIKE these they are capable of a LOT of power - you can take them apart into individual modules and then reconfigure them to enable the best for your car
They are not actually that much larger than the others when you do that
 
1 - 20 of 29 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top