Adding these electric motors to the back wheels of my FWD gas car?

[freebeard]

Originally Posted by jray3

Thanks Freebeard, Is that VW engine case as rare as it looks? I'm guessing freshly prepped 25 hp/ 1100 cc?

That might be. It was sold to me as a 36hp case. From TheSamba.com :: View topic - Stone stock 36hp engine, what does that mean to you?

The Beetle by Etzold. His Engine Identifications pages (219-221) show 36hp engine numbers from #695282 in 1954 through #4050000 in 1965-also noted as "final" engine in the series!

It's ID number is 3261377. It's got road rash on the sump fins but the mechanic who checked it over said it would need to be machined to take standard sized 36hp main bearings. So who knows. Some minor scuffing in the lifter bores.

After my first trip to Bonneville, I was interested in the 36hp Challenge. More lately I want to get a way from gas engines. But if I had an Arcimoto SRK, I'd probably start thinking about a half Vespa motorscooter pusher.

[electrabishi]

Originally Posted by jray3

On projects like this I'm not worried about synching up the electronics between engine management and motor control. The engine will behave like it's going downhill. (Just like operating my ICE pusher trailer behind an EV.) The electric rear axle could be completely independently controlled, preferably with a hand throttle, or if off the same accelerator pedal; through a master switch to enable/disable the Warp drive.

However, I think this car will be too difficult mechanically. On any car it is difficult to put one series motor on each rear wheel unless they are offset by using a gearbox, as there's not enough width for two motors, half shafts, and CV joints, let alone at the right angles. Putting a differential beneath a body that wasn't designed for it might be doable if you don't mind a big hole in the floor.
Also, this dual rear motor approach with one per wheel has been oft discussed, but very rarely implemented on a DIY EV. As I recall, the Tropica was then only series-motored 'production car' to do it, and not particularly well at that.
Polychain belts and their cogged pulleys are noisy.

I'd still love to french a motor into the driveline of a pickup one day. That would be much easier.

Hi Jay, Its good to see you here. I've been out of this stuff for a while. What ciano22 wants to do is totally doable. He even showed pic up under the car and all the worries I would have are alleviated.

First I want to state that I am not so up on joining yet another forum. Too many over the years got me too many house projects that have got me in trouble with the spousal unit. But EcoModder sounds like a cool one to me and right up my alley as a Certified Energy Manager.

Next I want to say that its good to see other EV (and NEDRA) guys on this forum. If there EVer was an ecomodder it has to be an electric vehicle guy. Maybe Jay has told what he gets for GGE. For me its about 100 MPG on my truck. But thats an analysis based on current cost of gas. Price of gas goes up my GGE goes up too :-)

And now to get to ciano22 project. Its totally doable. I'm going from memory but I thought you said the Impala makes 327 ft-lbs torque. And that you want more than that to the rear wheels to get the car moving. I can tell you than my 1978 Pinto with two WarP 9" motors puts 1500 ft-lbs to the Dyno. That is likely way more than you want to put what I think your desires are. So don't be sold on bigger is better and try to stick 11" motors up under the rear end.

9" motors may be more than you are looking for. And for your budget doing dual 9's will put you slightly over your $10k budget because you also have to consider the motor controller and batteries.

Now for batteries you don't really have to go too big because you are just wanting the motors for accelerating from slow speed. Aside from what many might think it does not take that much energy to accelerate a car to 60 mph compared to what it takes to just drive it for 10 miles (at that same speed). Think about it 180 HP for 15 seconds compared to 10 HP for 600 seconds. Although not really a unit of measure, it is in my mind. 2700 HP-seconds or 6000 HP-seconds. Its the same amount of energy. So you say the car makes plenty of HP at speed. That means it makes enough to slowly charge the 2700 HP-seconds you wasted accelerating at a high rate over the next few minutes. So really the Hybrid approach is a good idea. And it works the same way for other hybrids.

So the question you have to ask is how much "extra" torque do you need? As I said my twin 9" motors make 1500 ft-lbs. Although torque tapers off quickly with RPM, that's where a good string V* just getting up into its HP band would be useful.

If you want 3000 ft-lbs go with dual 11" motors.
If you want 1500 ft-lbs go with dual 9" motors.
If you want about 1000 ft-lbs go with dual 7" motors.
You could probably even get 600 extra ft-lbs with dual 6.7" motors salvaged directly off an old forklift.

The problem with the "differential movement" fixes itself with two motors wired in series from the same controller. Imagine if you were to mount two motors on top of a straight axle of a front wheel drive car. Put a gear inside the hub and mount a series would DC motor to it with about a 3:1 gear reduction. With the motors in series they will always have the same amount of current (and voltage) when they are turning the same RPM. BUT, if one starts to slip and the RPM is faster, the back EMF on the motor will drop. The other motor with the slower RPM and higher back EMF will have a higher power split from the batteries. With the same current flowing through them, the motor with the higher Back EMF on it will pull more power. Higher back EMF X same current is > than Lower back EMF X same current. So its a natural Differential action.

So the long and short is that what ciano22 wants to do is readily possible. You just have to figure out how to mount the motors to an axle that connects the two rear wheels. If as he says he wants to start with smaller motors he could do that. Two 6.7" motors cost $600 each. A Zilla 1K costs $2k (I think - its been a while) and 30 XE-16 lead acid batteries cost $3k (LiFePO4 would cost more)(but there are other more power dense Li- based batteries that would be suited to just jump starting). I have the idea on how to do that if he wants to contact me off list. I won't share the details until we get a working model, which I have been thinking of doing lately on my 7.3L Powerstroke Diesel. :-)

The guys at NetGain which makes the WarP motors have a kit for that by the way.

Cheers
Mike

[freebeard]

That's interesting. Is the 'natural' differential action proven or theoretical?

I'm not so sure about DC motors and lead acid batteries. The Warp 9 graph shows ~12 to ~28hp. How much does it weigh?

Here's a water-cooled 20hp polyphase DC altermotor that costs $512.32:

24266687 - OEM GM GENERATOR GMPartsCenter.net



It wants 115 volts. Instead of hanging two Warp 9s on a beam axle: Two of the Buick/Impala part mounted at one pivot of a swing arm with the 7-groove V-belt to the axle. Un-sprung weight would go way down. First 'gotcha': belt tension might affect wheel alignment.

ZF have shown a twist beam rear axle with geared reduction:


http://www.zf.com/global/media/product_media/cars_5/cars_chassis_etb/ZF_cars_eTB_PF_corporate_pf_teaser.png

Maybe the Buick belt drive could be replaced with a gear reduction.

Price of gas goes up my GGE goes up too :-)

Edit: That equation has two sides; I pay 5.3¢ per kilowatt hour. If I go across the river to the next town, it's ~10¢. Anyone who finds themselves on the Eastern coast of this great country will pay ~15¢ for electricity rolled from coal.

https://www.youtube.com/watch?v=5vLZOKshJPs

[electrabishi]

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[electrabishi]

Post #5 now I can add links :-)

[electrabishi]

Although I haven't seen any research papers on the subject with respect to this application, I can prove it to you. Or you could prove it to yourself. Go get two small DC motors. Little ones like you find in a cheap kids toy car. Wire them in series across a 6V battery. They will both start spinning about the same speed if they are the exact same motor. Then grab onto one motors shaft and slow it down and you will hear the other one speed up. You could go even further and totally stop the one motors shaft. Although the torque will increase on this motor, the other motor will spin a lot faster. Just remember the current will always be the same through the series circuit. The motors will share their voltage in direct proportion to their speed.


Warp11 weighs 243#
Warp9 weighs 143#
Warp7 weighs ~100#
A 6.7" motor weighs ~67#

Be careful in reading the Motor Torque RPM charts. They can confuse you if you are not familiar with all the test conditions. For example the torques shown will be at a certain speed with a certain load on the shaft. For accelerating from a stop try to find the locked rotor torque and it will be extremely high. And as the RPM on the motor rises the torque will slowly drop. And as Jay said it will also work naturally with the gas engine taking up at higher RPM as the torque on the electrics drop to almost an insignificant contribution.

Dyno results for my Pinto are here http://www.dragtimes.com/1978-Ford-P...phs-15453.html

Other details here http://www.dragtimes.com/Ford-Pinto-Timeslip-15453.html

and here Mike Willmon's 1980 Ford Pinto


Yes adding these motors to the beam axle will increase unsprung weight. Which is I would advise not to go with a WarP11 motor, thats way more than is needed for the desired outcome. I might argue more for a 6.7" or the WarP7 (which is 7.25"). Mounting right to the axle would allow coupling to the hub with a gear set or a 50 roller chain. Tension would be taken up in its mount and would not change with position of the axle.

[freebeard]

Although I haven't seen any research papers on the subject with respect to this application, I can prove it to you. Or you could prove it to yourself.

We (royal wee) like papers, but A-B-A testing rules.

But can it do torque vectoring? FOC motors are persnickety about their phasing, but once that is accommodated in software, torque vectoring becomes possible.

For accelerating from a stop try to find the locked rotor torque and it will be extremely high. And as the RPM on the motor rises the torque will slowly drop.

My understanding was that it rises until the back-EMF kicks in and it flatlines. Maybe that's the polyphase motors again?

The weights don't seem out of line, but putting one on a clutch and transmission sounds counterproductive to me. This single speed installation would be better. EV West just did a conversion on a Fiat 124 and immediately made the clutch disk into two parts. Gas motor drive trains don't expect the microsecond shock loads.

Tesla doesn't do it. Arcimoto doesn't do it. But, Wolftronics make a 2:1 planetary gear box that will pass 500hp.

*Take all this with a grain of salt. I'm still gathering parts and info for my first EV conversion, as thingstodo can attest.

[Stubby79]

Originally Posted by freebeard

The weights don't seem out of line, but putting one on a clutch and transmission sounds counterproductive to me. This single speed installation would be better. EV West just did a conversion on a Fiat 124 and immediately made the clutch disk into two parts. Gas motor drive trains don't expect the microsecond shock loads.

Tesla doesn't do it. Arcimoto doesn't do it. But, Wolftronics make a 2:1 planetary gear box that will pass 500hp.

As I mentioned in another thread, it's about RPM range. The poly-phase motors production EVs run can do 10 or 12,000 rpm. These DC motors are limited to 5 or 6k. The production EVs run ~10:1 final drive. If you did that with only 5 or 6k peak, you'd only be able to drive around town. If you cut the ratio in half, you'd kill your acceleration, or else require a hell of a lot more amps to make it acceptable. Which means a bigger motor and a bigger controller. More weight and much more $$.

So lets say you do it anyway. You're now running twice as many amps on take off. Amps = heat. And heat = inefficiency. Your efficiency goes to hell at low speeds. Compounded if you use lead acid batteries. (I believe, back in the day, the rule of thumb was that that direct drive cut your range in half.) Worse....your motor is air cooled by a built in fan that's driven off the motor itself. It's not spinning fast enough to shed regular levels of heat, let alone the extra heat being made by all those extra amps. You'll either have to add force air-cooling, or risk overheating and killing your motor. Half the reason for running a bigger motor is the sheer mass of copper...more thermal mass to absorb all that heat.

Heat in a production ev motor isn't nearly as big of a worry. They're liquid cooled, independent of motor speed. They have that 10:1 gear box, so they're not "lugging", and they only require half (or less) as much torque to get the same results. They're also more efficient at low rpm, so there's less heat to begin with. All-around better. That's what happens when things are purpose-made for their application, I've noticed...

Speaking of purpose-made...there's a 2-speed powerglide transmission out there for EVs, sans torque converter. Plenty strong enough, and gives you that gear ratio change you want to go with DC motors. Not cheap, though. Perhaps one could convert an old powerglide for a lot cheaper?
Powerglide 2 Speed Direct Drive Transmission for EV Motors - EVGlide, EV West - Electric Vehicle Parts, Components, EVSE Charging Stations, Electric Car Conversion Kits

And, before I forget, you want to also note the torque curves of series-wound motors.



Due to the self-weakening field nature of series-wound motors, you generally start to run out of torque above a two or three of thousand RPMs(vs an AC motor with a pretty flat torque curve). To get more torque, you need to cram more amps in to it, and the only way to do that is to overcome the back EMF with a higher voltage. If you don't...well, 5 or 6k rpm might be your motor limit, but it becomes useless well before that. You'll never get up to speed that way.

IMO, these Netgain/DC motors are designed to replace an ICE directly, and they work well when used as such, but for other applications, there are better suited motors.