# No differential with Twin Motors?



## Normsthename (Jul 13, 2008)

On another thread I am contemplating converting a small Microcar over to electric.
A lot of folk tell me to junk the CVT Transmission and to run it direct.

I was wondering if I could also junk the gearbox and use twin motors to drive the front wheels indivdually?
Would it work without the differential in the gearbox, and when turning would the outer motor freewheel?
The ICE Gearbox only has a Forward - Neutral - Reverse Gear.

Andy


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## Qer (May 7, 2008)

I've been pondering the same thing, but the main problem is that the wheels turn with a pretty low rpm. If you can find motors with fitting gear boxes that gears down the speed 1:4-1:6 somewhere (not sure about the best number here) it might actually work, but most motors won't like to be directly connected to the wheel unfortunately.

There's a thread somewhere in the forum where people are planning DIY wheel motors. That'd be the other option for you. I've skipped it since I know myself. I better keep it simple or I'll never finish the conversion.


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## Normsthename (Jul 13, 2008)

Thanks QER, I think that you could be right.... 
I have calculated that my Microcar with its 13" Wheels at 60mph would be turning at only approx. 1150 rpm
So if you fitted an electric motor with a maximum rev limit of 3500 rpm, it would need gearing by approx. 3:1
If you used a chain and sprocket to change the gearing, the smallest sprocket that you could comfortably use would be approx. 17 teeth
The large sprocket would then need to be 52 teeth, which would be approx. 200mm (8") in diameter.
It would not be a very clean installation with two chain and sprockets thrashing about under the Bonnet (Hood) 
*UPDATE
*Just found a company that sells small plantetary gearboxes that would do the job.
Trouble is they cost £850 ($1700) each 

Andy


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## Jeremy (Jul 12, 2008)

I'm pretty sure that you could get away without a diff, as the two motors would just adjust speed pretty automatically as the torque requirement between each wheel varied when cornering.

The topic of DIY hub motors is interesting though, as it brings up the possibility of a very neat installation.

What might be worth looking at, at least for a very light car like a microcar, is whether or not some of the bigger electric bike hub motors could be adapted. The big Crystalyte 5302 brushless motor, for example, will deliver about 5kW max, around 160Nm of torque and a max speed of around 60mph on 72V. If four of these could be adapted to fit into car hubs (lots of engineering challenges!) then it seems possible to build a four wheel drive vehicle with quite reasonable performance.

An easier engineering challenge might be to look at whether or not some of the bigger scooter wheel motors might be adapted. These seem to be available built in to alloy wheels that might be made to work on a very light microcar. A quick Google revealed one or two Chinese motors, like this: http://wolong.manufacturer.globalso...or/1001489954/Brushless-DC-Electric-Motor.htm

There's also the expensive UK manufactured option from PML, here: http://www.pmlflightlink.com/motors/wheelmotors.html

Jeremy


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## Normsthename (Jul 13, 2008)

Thanks Jeremy (Again!)
Some interesting ideas you have there 
I have emailed the PML Company some questions.
I like 'Engineering Challenges" 
I have most tools at my disposal, TIG Welder, Lathes, Millers etc.
I also have an Homebuilt CNC Plasma Cutter that would be great for cutting Engine Plates out. It can cut a maximum of 19mm (3/4") Steel 

I had another idea of fitting two 7.5Kw 'Pancake' Motors back to back, and then modify the Half-Shafts to fit onto these motors.
The only problem I can see is the relatively Low Maximum RPM (1200) of the wheels
I don't think that the motors would be running very efficiently?

Andy


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## Qer (May 7, 2008)

Normsthename said:


> The only problem I can see is the relatively Low Maximum RPM (1200) of the wheels


I think that sounds like a perfect match. An ordinary 185/70-tire rolls 1.95 meters per turn, which gives that 1200 rpm would give you a maximum speed of close to 140 km/h (about 85 mph). You need to go anywhere faster than that? 

What would those motors cost?


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## Normsthename (Jul 13, 2008)

The 1200 rpm was based on the cars 13" Wheels turning approx. 1200 rpm at 60mph
The 'Pancake' Motors that I was referrring to run at approx. 3500rpm when making there maximum power
So if it was driving the wheels direct, the motor would be running very inefficiently.
If the car could travel at 180mph then those motors would be ideal! 

Andy


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## Qer (May 7, 2008)

Ah. I see. Ok, then it might be a problem, yes. Depending on the motor it might not be a problem with efficiency, but it'll be a LOT of current running through it so either the motor might burn up due to the current OR it'll be a lot heavier than needed to be able to handle the load at low rpm's. Using a fan to cool the motor might also be a path to be able to use an undersized motor for a too big task.

Lots of or and might here though.


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## Apex-xt (Jun 27, 2008)

I recall that there was a recent announcement (last month or so) of a company that is using a Saturn VUE and using 2 motors to direct drive the front wheels and a 3rd motor connected to a rear diff driving the 2 rear wheels. They stated the rear motor would only turn on when increased load or spinning of the front wheels occurred or driver elected AWD. They were looking for a company to pick them up and stated that if that didn't happen, they would begin mass producing themselves. They had already struck up a deal with Saturn to obtain VUEs from the TN (?) plant sans engine and drivetrain. There wasn't information about distance capability. It can be done.


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## Jeremy (Jul 12, 2008)

Connecting hub motors to the drive shafts certainly eases the engineering challenges a great deal. If you could make do with around 10kW peak then a couple of brushless 5302s would do pretty well, if run at 72V. These are about $450 each, plus the cost of suitable controllers. I've just run the numbers (using the ebikes.ca simulator) for a 5302 on 72V with a 100A current limit (which may be a bit high).

Maximum power = 5,500W (7.4hp) at 1050rpm

Maximum torque = 140Nm at 0rpm, dropping to 50Nm at 1050rpm

Efficiency = 65% at 500rpm, rising to about 85% at 1150rpm (about 82% at 1050rpm).

One concern with these motors would be whether or not you could run 100A through them. I'm fairly sure that some of the guys over on the ES forum have worked these motors up at this sort of power though - I recall one post over there where the chap had laced one of these motor into a motorcycle wheel and run it up to around 7kW, I think.

Another issue would be whether or not 280Nm of torque at the wheels would be enough to give adequate initial acceleration. I've no real feel for this though - maybe someone else here knows how much torque is needed for start-up performance to feel OK. 

I'm sure a bit of digging around might find better candidates though, such as some of the more powerful scooter hub motors. The rpm range you need is right around the right ball park for most big hub motors - big scooter wheels have a similar rolling diameter to small car wheels I think.

Jeremy


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## skullbearer (Jul 9, 2008)

You could go with an AC motor as well, 6 phase AC motors are very high efficiency and torque, but have a peak of 1200rpm in most cases. For a direct to wheel match that seems ideal.

Otherwise you just have to look into connecting via planetary gearbox or fix sprockets. Maybe weld a sprocket onto the drive links for the wheels. The biggest challenge I see for doing non-wheel motors for individual wheels is the suspension travel... but you get around that by using the existing universal joints on non-solid axle vehicles.


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## Normsthename (Jul 13, 2008)

Thanks Skullbearer.
AC Motors do sound ideal for the job, but they also sound very complicated....... 
I need to read up a bit on these to get upto speed on them 

Andy


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## skullbearer (Jul 9, 2008)

You and me both... if anyone knows a VERY thorough source anywhere?


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## Qer (May 7, 2008)

Normsthename said:


> AC Motors do sound ideal for the job, but they also sound very complicated.......


Yeah. I've been realising AC would be ideal for a conversion. Then I've been thinking more about it and reached the conclusion that AC would be ideal for a second conversion. Or third. Possibly fourth. 

My first one will DEFINITELY be DC! I'm probably gonna end up with a car that feels like "Sure, it runs, but it could've been better" no matter how I do it, so I've decided to go for KISS. Just get it up and running to actually finish one, then go all fancy on a second project when I've proven to myself and everyone else that I can do it. I bet the WAF is better on a second project when it runs way over budget when the wallet already tells the tale of saved gas money from the first one.


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## Normsthename (Jul 13, 2008)

I think thats a good approach Qer 
Last year I built a CNC Router / Plasma machine from scratch, and I used KISS on that 
I am now looking at designing and building a MK2 CNC Plasma machine which will have so many more enhancements that I have learnt from building MK1

On the subject of EV's I am thinking about doing a Motorcycle EV first before I tackle my Microcar.
Once I have done the bike, I think I will be in a much better position to do a good job on the Microcar 

Andy


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## skullbearer (Jul 9, 2008)

Sounds like a plan... did any of you guys get this link? Someone provided it in one of the other threads on building a 90hp AC motor from a 2hp one, I'm going through it right now but it seems pretty thorough (at first glance so far)

Texas Instruments crash course on 3-pole AC vector controls

EDIT: I think I need a little more math and electrical engineering background to follow that, but it did answer my questions as to what kind of AC motor and controller to look for at least.


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## morvolts (Jun 19, 2008)

skullbearer said:


> You could go with an AC motor as well, 6 phase AC motors are very high efficiency and torque, but have a peak of 1200rpm in most cases. For a direct to wheel match that seems ideal.
> 
> Otherwise you just have to look into connecting via planetary gearbox or fix sprockets. Maybe weld a sprocket onto the drive links for the wheels. The biggest challenge I see for doing non-wheel motors for individual wheels is the suspension travel... but you get around that by using the existing universal joints on non-solid axle vehicles.


tell me more about the 6 phase motor
also whats this about turning a 2 hp AC motor into 90HP?


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## xrotaryguy (Jul 26, 2007)

Most Ac motors are designed to work on 50Hz or 60Hz AC from the grid. That's why they have ratings like 1200 rpm or 35oo rpm etcetera. To control the speed of an industrial AC motor you'd need to install a reluctor and a pair of hal effect sensors and buy a variable frequency drive or build your own. That's getting pretty complicated for a microcar conversion. I would suggest a couple of forklift-sized motors that chain drive either wheel. You'd basically need to build your own chain drive setup, but it's been done before. It's very doable.


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## Normsthename (Jul 13, 2008)

> Another issue would be whether or not 280Nm of torque at the wheels would be enough to give adequate initial acceleration


Jeremy, are you sure that 280 Nm is correct?
According to the 'Net' to convert from Nm to lb.ft. you multiply by .7376
280 * .7376 = 206.52 lb.ft. 
My car only has about 36 lb.ft so if it had 200+ it could pull a tree out by its roots 

Andy


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## Jeremy (Jul 12, 2008)

Andy,

Those torque figures are correct, but they are at the wheel. I suspect that the torque figure you quote is at the engine flywheel.

I'm not sure what the overall reduction ratio for your microcar in "first" gear is, but would guess that it's probably quite high, maybe around 15:1.

An ICE will not give it's maximum torque when pulling off, most probably it will deliver around half the maximum figure (complete WAG!). If this is the case then your engine may give around 18 to 20 lbsft when pulling off, which could be multiplied to around 270 to 300 lbsft at the wheel. If your CVT allows the motor to deliver maximum torque when pulling off, then that ups the torque at the wheel to around 540 lbsft.

If my complete WAG above is correct, then two of those motors may not really give you enough torque to give brisk acceleration from low speeds, I suspect. I think that you probably need to look at some of the more powerful scooter wheel motors, as they may well deliver the sort of power/torque you need.

Jeremy


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## evallan (May 28, 2008)

I have thought of two motors but I suspect a complex system would be required to avoid one side pulling just a bit harder than the other making it hard to steer. For me there are enough challenges in building an EV without attacking that one.

evallan


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## skullbearer (Jul 9, 2008)

evallan said:


> I have thought of two motors but I suspect a complex system would be required to avoid one side pulling just a bit harder than the other making it hard to steer. For me there are enough challenges in building an EV without attacking that one.
> 
> evallan


It seems to me that,

Assume: Both motors are matched (identical) and in equally good operating condition,

Let: Voltage-1 = Voltage-2, and Amp-1 = Amp-2 (1 and 2 being the motors), such that Watts-1 = Watts-2,

Then: MotorPower-1 (being the power outputted by Motor-1) + MotorPower-2 = TotalPower, and given that the output power draw on a motor, say Motor-2, is:

TotalPower - MotorPower-1 = MotorPower-2


We can conclude from this that as the power in the stronger motor increases, the weaker motor is equally relieved of strain, and when the strain is relieved, then we go to the velocity function:

Velocity(time) = Acceleration(time) + Existing Velocity - Drag - Roll. Res.
(with respect to time)

As Velocity increases due to the extra acceleration from the stronger motor, since Existing Velocity is a constant (in the case of a vehicle monitored from stop, Existing Velocity = 0),

This means that Acceleration increases proportionally to Velocity.


In simpler terms that give me less of a headache,

As the stronger motor spins faster due to its acceleration, the other motor spins faster due to the higher speed of the vehicle and reduction in resistance, this combo of two factors which will increase velocity of the weaker motor to match and give it a greater acceleration and thus power output and...

Both motors will pull the same. ALL GIVEN THAT POWER INPUT IS EQUAL!

Am I just blowing mathematic diarrhea out my butt?


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## evallan (May 28, 2008)

The main assumption is risky. No matter how evenly matched two motors are one will put out a little more power than the other. When they are driving the front (steering) wheels I have a nasty feeling the car will not want to go in a straight line. If two motors were driving rear wheels I think it would work fine

evallan


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## Qer (May 7, 2008)

evallan said:


> The main assumption is risky. No matter how evenly matched two motors are one will put out a little more power than the other. When they are driving the front (steering) wheels I have a nasty feeling the car will not want to go in a straight line. If two motors were driving rear wheels I think it would work fine
> 
> evallan


At least if you have power steering I don't think you have to worry. We had a bad front brake on one of or cars which made the car drag right when accelerating and left when braking but it wasn't any problem holding it on an even course despite that.

Eventually the brake locked up at a hard deacceleration (because I was lazy and didn't look at it in time) and after that the automatic transmission refused to go higher than second gear despite an RPM close to the end of the scale. The car wanted to constantly explore the wonderful nature of the right ditch but a firm grip of the wheel (aided by power steering) still easily kept the car going straight on the road.

I won't go into details about how long time it took to dismantle the brake or how many nasty words I invented in the process, but let's just say it was properly jammed and well beyond all recondition attempts.

So in short; it's possible the two motors will make the driving a bit uncomfortable if the car tries to pull uneven, but it won't be a security risk.


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## Jeremy (Jul 12, 2008)

I think the issue of pulling to one side is a non-problem. My reasoning is based on the many tens (may be hundreds) of thousands of vehicles that are driven in this way every day and don't have a problem.

Virtually every electric wheelchair or mobility vehicle has separate motors driving the wheels, yet they drive in a straight line. Similarly many battle robots use similar drive systems and they stay in a straight line also (although rarely do so, for tactical reasons). I built an autonomous electric lawn mower with twin motor drive a few years ago (it was a failure for other reasons) but that also went straight with no tweaking of the controllers at all. In fact it's accuracy at staying in a straight line caused me additional work with the control algorithm, as I was hoping to get a degree of pseudo-random behaviour from it deviating from a straight line (I wanted it to randomly swing around to better ensure the whole area encompassed by the "corral" wire was evenly covered).

There is at least one prototype wheel motor car I know of, the PML Mini conversion, plus the new generation of military high-mobility wheeled vehicles are also looking at using wheel motors with hybrid drive. 

I strongly suspect, based on all this evidence, that individually driving wheels with separate motors will be absolutely fine.

Jeremy


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## OHM (Jun 30, 2008)

Lee Hart has already highlighted the issues of using twin AC motors and DC motors in this manner.
The DC is the one that adjusts itself acting like an LSD when you run one for each driveshafts the AC dont.
The solution would be to have for eg. and Im willing to do a group buy for such a custom setup if anyone else is interested?

Large diameter short length DC motors that max out at 1500-1800rpm

This would mean chopping up the biggest DC motor say a 13inch motor and making it about 9 inches wide plus shaft. Then you could stach them facing their shafts away from each other and a central blower above them diverting into two streams.

We need a specialist DC motor builder and to consider whether we would use series or even better a Sepex setup. I would prefer Sepex as there are 2 controllers available from Electrosistem and Zappi.

http://www.elektrosistem.com/e/p2.htm

http://www.elektrosistem.com/xtra/53 - News PHOENIX ING.pdf










http://www.zapiweb.com/details.php?lang=eng∏=21&type=Technology&id=5










The electrosistems Phoenix t81/82 is rated at 25.6kw but not sure if that is nominal or peak anyone know??



> The Phoenix control units have been designed for the
> drive of separately excited motors and are divided into Pho-
> enix T60 suitable for motors from 4.8 Kw to 16 Kw and
> Phoenix T80 suitable for motors from 12 Kw to 25 Kw
> ...





> Rated current ............................................................................................................................................ 600A - 800A
> Multivoltage ............................................................................................. 24 / 80V or 96V or 120V (-33% +20%)
> Operation frequency ............................................................................................... 15800 Hz or 7900 Hz for 120V
> Max. ambient temperature ........................................................................................................................... -20 +40°C
> ...


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## Jeremy (Jul 12, 2008)

Whilst I agree that two synchronous AC motors would give the problem of no differential action, it would be fine to use a pair of non-synchronous (conventional brushless) AC motors in this set-up.

Brushless AC motors of this type use feedback from the back EMF of the motor windings, or separate Hall rotor position sensors, to determine rotor position and hence phase drive requirements. Such motors behave pretty much like brushed DC motors when subject to a varying load so would give adequate differential action.

Jeremy


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## OHM (Jun 30, 2008)

Jeremy however the controller is a big issue as you need two of them while with two dc you only need one, no?

The Tango is a good example of using two directly connected DC motors.

I personally would love to run two AC motors, one to each driveshaft and have found that Leeson do the lightest AC motors compared to other industrial motors for the same performance but controlling them is beyond me.


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## Jeremy (Jul 12, 2008)

Yes, you do need two controllers to run the motors asynchronously, but a couple of controllers capable of handling around 7 or 8kW each (which is what this particularly project needs) wouldn't be two big an overhead cost, I would have thought.

I don't have the costs for brushless controllers to hand, but if the cost differential is similar to that for big and small brushed controllers then two smaller ones might not cost much more than a single big one, in fact it might even be cheaper. For example, an Alltrax 4834 (14.4kW) is about $300, whereas an Alltrax 7234 (21.6kw) is about $480. The smaller controller is under $21 per kW, the bigger one comes in at over $22 per kW.

Other system components, like the contactor and main fuse, could be shared to keep cost and complexity down. In fact there would be safety reasons why you'd need to share the contactor, as it would be desirable to ensure that both motors get shut off from the same point.

Jeremy

Jeremy


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## skullbearer (Jul 9, 2008)

I'm not sure if you're suggesting using multiple controllers per each motor or just that the individual motors would be under 14.4kW... is it possible to use two controllers on a single motor circuit without issue? It seems to me if the controllers have a system to prevent runaway spins when load drops too low (wheel spin, or wheel in air) that they would freak out at double amps as well...

I don't know.

On the note of double AC motors, I've been talking with a buddy of mine who has a degree in this stuff... there was another gentlemen mentioned the same thing I think on the 'building a 90hp motor' thread, its not an EE but its like a lower level version.

Anyway, my buddy has been doing RC and go-kart scale EV work for 18 years, and he claims DC actually out efficiencies AC in all vehicular applications, the only drawback being the larger motor sizes. What he's saying doesn't reflect all the claims about AC I've read/heard, but he's done both AC and DC vehicles and he is adamant that the DC system is better.

Then again, he also has some crazy conspiracy theories about the whole deal so I'm not 100% on it.


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## Qer (May 7, 2008)

skullbearer said:


> I'm not sure if you're suggesting using multiple controllers per each motor or just that the individual motors would be under 14.4kW... is it possible to use two controllers on a single motor circuit without issue? It seems to me if the controllers have a system to prevent runaway spins when load drops too low (wheel spin, or wheel in air) that they would freak out at double amps as well...


Two controllers for a DC-motor might work, or they might freak out and your drive will be jerky and spasmodic, possibly burning up the controllers as well. But it MIGHT work, much depending on the construction of the controller.

Two controllers for a AC-motor will be Ragnarok. *ker-blam* *tinkelinkelink* Magic smoke will leave the box and the controllers will be dead. Don't do that.

In general, you should stick to one controller per motor, period. Exception: A DC-controller can safely control two or more motors, but the maximum power per motor will go down. Sometimes this can still be a good idea, like if you run two small motors on one big controller.


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## OHM (Jun 30, 2008)

I would certainly want more than 8kw per side so this is an issue.

I would prefer one controller say a Sepex with two large diameter short length DC motors.

As for effiency and cost I think the Sepex DC is often overlooked for what it provides.


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## Jeremy (Jul 12, 2008)

> I would certainly want more than 8kw per side so this is an issue.


So would I, but the OP has already said that he's legally restricted to 15kW total power for this class of vehicle. This is the reason that much of the discussion has focussed on relatively low power solutions.

Jeremy


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## OHM (Jun 30, 2008)

AHA 15kw is the requirement pardon me. 

If any case more is required a Zappi or electrosistems dual Dc controller would be interesting.


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## skullbearer (Jul 9, 2008)

Where can you find the legal limits for different vehicular classes?


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## Jeremy (Jul 12, 2008)

> Where can you find the legal limits for different vehicular classes?


My guess is that there is a great deal of variation from country to country. Europe has a semi-unified system of vehicle Type Approval, but even here there is a fair bit of variation between individual European countries.

In the UK, the various categories are listed on the Department for Transport website, but are far from easy to find. I don't know whether or not common rules apply across the whole of the US, or whether there are individual State rules that apply.

Here in the UK (where the OP hails from) we have some pretty draconian regulation on cars, particularly with regard to Type Approval. This really hits people doing major modifications or building completely new vehicles, as they have to put the finished vehicle through a full Single Vehicle Approval test, which is pretty tough.

We have some ways around this, for example, my motorcycle conversion just gets away without having to go through this test by retaining most of the parts from the original motorcycle. If I'd used a different set of front forks, or new wheels, for example, then I'd have to put the thing through the Motorcycle SVA test. The daft thing is that the original 1986 motorcycle I've used as a basis for the conversion wouldn't pass the modern MSVA test, it would fail on a host of things, like the edge radius of most of the projecting parts not being great enough to pass the pedestrian collision criteria (I jest not - you guys in the land of the free don't know when your well off..........)

Jeremy


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## skullbearer (Jul 9, 2008)

Jeremy said:


> My guess is that there is a great deal of variation from country to country. Europe has a semi-unified system of vehicle Type Approval, but even here there is a fair bit of variation between individual European countries.
> 
> In the UK, the various categories are listed on the Department for Transport website, but are far from easy to find. I don't know whether or not common rules apply across the whole of the US, or whether there are individual State rules that apply.
> 
> ...


 
A good point, guys like me in the land of the idiots, err, the free don't really have as hard a time as that.

HOWEVEVER, several people in person have told me that the DMV has some wacky restrictions (In CA specifically) regarding electric vehicles.


To go on main roads they must be able to maintain 55mph for a short time... it was only like 4 seconds or something, which is a ludicrously short time to expect a vehicle to maintain freeway speeds ON THE FREEWAY.

Not to mention it has to have very specific distances and materials (basically steel, steel, or steel, oh yeah, there's always the steel option) between the cab and the outer edges of the vehicle on front and back, though there don't seem to be any real standards for the sides (other than that they exist in some form).

There has to be some way of locking the vehicle, or so I'm told, even though there is no expectation the vehicle be unenterable while locked... (anyone remember those canvas topped Jeeps you could just unzip, get inside, and then murder the occupants? If they didn't roll it and murder themselves first).


I'm also told for some reason that if the car is under a curb weight of 1600lb and is electric, it cannot exceep 14.4kw of power.


The really wacky thing is the DMV and government websites related to this basically pretend custom EV's don't exist except in fantasy novels, and only talk about conversion requirements (which are not severe). All I can glean from a direct source (including the DMV counter itself, god that was a wait just for a 10 second answer) is that the only way to be sure you're meeting the criteria is to build the vehicle, take it to the DMV, and have it inspected. Then take it to a DMV approved body shop and have it inspected. Then take it to a DMV approved engine/drive shop and have it inspected. Then take it to a DMV approved electrical shop, and have it inspected.

All at your expence, according to the overworked overweight woman at the counter. She expects it would be between $300-800 for the inspections based on the complexity of the vehicle and difficulty to inspect it, plus there are only 500 custom vehicle slots available per year for road registration, of which some many thousands of custom hot-rod builders with nary an EV are competing for.

Supposedly the best way to get one of those custom vehicle registrations is to head to the Sierras, which have DMV's an hour ahead of the valley/coast DMVs, and register it within the first open hour. By the second hour, they will surely have used up the 500 custom registrations.


Plus every time you modify the frame, shell, or drive components of the vehicle you are required to submit it for re-inspection.



If anyone can give me a link to substantiate these things, I would appreciate it... so very much. Especially if it proves most of them wrong.


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## Jeremy (Jul 12, 2008)

It looks like bureaucracy is the same the world over.............

I have a theory that the spread of nanny-state regulations will so wrap the population up in cotton wool that natural selection will lead to the downfall of the human race. I believe that we need to take risks and do things that have an element of danger in them, just to maintain the skills we need to survive changes in our environment. Having seen a hair dryer with a warning label on the side that read "Do not use in the bath" I have a feeling the dumbing down process is well under way.

Best stop this though, as I might start an off-topic rant about over-regulation and over-protective safety laws allowing really, really dumb people to survive and breed when for the greater good of the human race we'd be better off with them taken out of the gene pool. 

Jeremy


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## john818 (Aug 1, 2008)

skullbearer said:


> A good point, guys like me in the land of the idiots, err, the free don't really have as hard a time as that.
> 
> HOWEVEVER, several people in person have told me that the DMV has some wacky restrictions (In CA specifically) regarding electric vehicles.
> 
> ...


None of this sounds right to me. Unfortunately, I'm no authority, but I've been crawling all over the California Vehicle Code and haven't seen anything about any of this. For those who are interested, here's a link to the CA Vehicle Code on the DMV site.
http://www.dmv.ca.gov/pubs/vctop/vc/vctoc.htm

One thing I think I recognize is the 500 registrations thing. What they're probably talking about is CA Senate Bill 100 and smog testing of "Specially Constructed Vehicles" which are mostly kit cars. There are 500 spots per year, and they're usually gone about noon or so the first day.

Here's a quote from http://www.dmv.ca.gov/vr/spcns.htm


> Per California Vehicle Code §4750.1, the first 500 program applicants in each calendar year may choose whether the inspection is based on the model-year of the engine used in the vehicle or the vehicle model-year. If the engine or the vehicle does not sufficiently resemble one previously manufactured, the referee will assign 1960 as the model-year.


Since EVs don't have emissions, this doesn't apply. I think you EV owners can just get a waver and not have to worry about the biannual inspections.

As far as the rest of it goes, I'd bet there's been a lot more confusion and miscommunication, but i don't have info or links to back it up.

Oh, BTW... Hi everyone! This is my first post.

Back on topic. I've been thinking about the no dif and 2 motors thing for a while now, but I don't have many answers yet and have barely considered what questions I have. My interest was sparked after reading this on EV Parts' FAQ...
http://www.evparts.com/page-FAQ.htm


> With series DC motors, the problem is trivial. Wire the two motors in series, and they behave exactly like a normal differential; same torque at both wheels regardless of speed. With one wheel in the air, you have no torque at the other wheel either.
> 
> Wire the two motors in parallel, and it behaves like a limited-slip differential. Each motor operates independently, adjusting its speed according to the torque. Same speed, same torque to both wheels. When you turn, the inside wheel slows down a bit, so it delivers a bit more torque.
> 
> ...


Sorry the quote is so long, but I thought a lot of the info would be interesting to many people following this thread.


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## OHM (Jun 30, 2008)

Yes this a good quote, the only thing is that the DC in parallel needs a special controller?

Also Ive been considering getting a 13inch motor and getting it chopped
up into a pancake style motor and using two such customized items.

This should decrease the rpm, increase the torque compared to say a 6.7 with more length but same amount of copper winding. Produce less heat and easier for heat to dissipate?, last longer and end up a tad lighter thanks
to shorter same thickness armature and shorter shaft?


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## alanfr (Aug 30, 2008)

You have a number of issues dumping the diff & cvt. Try imagining what happens if power fails to one motor? Also you are increasing the unsuspended mass - can the suspension cope. I noted the thought about using two 5302 motors. I did the calcs for a lightweight car (less than 700Kg) with 10" rims (overall tyre diameter 0.42m) and you need around 400Nm for sensible performance. Plus you need around 350Nm to go uphill (15% gradient at 10m/sec). How heavy is your car?? You can pretty much pro rata the above 400Nm by weight (if twice as heavy you need twice the Nm) and by the tyre size (if the tyre is 10% bigger you need 10% more power).

Good luck!


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## Normsthename (Jul 13, 2008)

> How heavy is your car??


The unladen weight is approx. 350kg 

Andy


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## alanfr (Aug 30, 2008)

You need to come up with a gross weight. Micro cars are around 350Kg unladen, but you will be removing engine, possibly cvt/diff. Then you will be adding the electric motor(s) and battery. 15KW electric motors can be up to 45Kg, battery packs can be 100Kg + - this depends on type as well as range etc you require. Finally of course you need to allow for passenger(s) and luggage. As has been mentioned (I think) 15KW is the max for a micro car anyway so you are limited by this (which means top speed may have to suffer if you are to have sufficient torque). As far as I can tell micro cars have to be under 400Kg but fortunately for an ev the batteries are not included in this limit.

What is the tyre diameter?

My earlier comment re unsuspended mass would only apply if you went to hub motors. I still worry about the safety of dual motors should one fail for some reason.

Sounds like you have a good workshop to try your ideas out!

Good luck!


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