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Group,
I've been thinking for a while about converting a rear wheel drive vehicle.
Specifically, I've been thinking of doing a BMW. The reasons for this are
that it seems to me that since the vehicle has independent rear suspension
and the dif is basically connected rigidly to the subframe, you could also
mount an electric motor to the same subframe.

This would allow doing away with the ICE motor, the transmission, and the
driveshaft. Seems like it would be a good way to go IF I can find the right
motor that operates in the proper rev range for being connected to the diff.

Any thoughts on this idea?

Thanks,
Brian

--
Brian Jeffries
xxx@xxx.xxx
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Transmissionless EVs have been beat to death over the last couple of
weeks. Check the archives.

[quote] Brian Jeffries <xxx@xxx.xxx> wrote:
> Group,
> I've been thinking for a while about converting a rear wheel drive vehicle.
> Specifically, I've been thinking of doing a BMW. The reasons for this are
> that it seems to me that since the vehicle has independent rear suspension
> and the dif is basically connected rigidly to the subframe, you could also
> mount an electric motor to the same subframe.
>
> This would allow doing away with the ICE motor, the transmission, and the
> driveshaft. Seems like it would be a good way to go IF I can find the right
> motor that operates in the proper rev range for being connected to the diff.
>
> Any thoughts on this idea?
>
> Thanks,
> Brian
>
> --
> Brian Jeffries
> xxx@xxx.xxx
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>



--
http://www.austinev.org/evalbum/1059
http://stormselectric.blogspot.com/
Storm

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[quote]Brian Jeffries wrote:
> Group,
> I've been thinking for a while about converting a rear wheel drive vehicle.
> Specifically, I've been thinking of doing a BMW. The reasons for this are
> that it seems to me that since the vehicle has independent rear suspension
> and the dif is basically connected rigidly to the subframe, you could also
> mount an electric motor to the same subframe.
>
> This would allow doing away with the ICE motor, the transmission, and the
> driveshaft. Seems like it would be a good way to go IF I can find the right
> motor that operates in the proper rev range for being connected to the diff.
>
> Any thoughts on this idea?
>
> Thanks,
> Brian
>
>
Without a transmission to change the gearing ratios, you'd be limiting
your top speed as a direct function of the max rpm of the motor, and
acceleration at high speeds could be reduced. You would also probably
have more clearance/spacing issues fitting in the motor and might need
to cut out part of the metal around the mounting location. On the other
hand, you might be able to save more weight than on a FWD car, and you'd
get the creature comforts of a BMW, assuming they still work on the
donor vehicle.

-hk

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This is not very typical conversion example, but is a BMW
you're thinking about:
http://www.evdrive.com/BMW_project/ProjectBMW.html

--
Victor
'91 ACRX - something different

http://www.evdrive.com/BMW_project/ProjectBMW.html


[quote]> Brian Jeffries wrote:
>> Group,
>> I've been thinking for a while about converting a rear wheel drive vehicle.
>> Specifically, I've been thinking of doing a BMW. The reasons for this are
>> that it seems to me that since the vehicle has independent rear suspension
>> and the dif is basically connected rigidly to the subframe, you could also
>> mount an electric motor to the same subframe.
>>
>> This would allow doing away with the ICE motor, the transmission, and the
>> driveshaft. Seems like it would be a good way to go IF I can find the right
>> motor that operates in the proper rev range for being connected to the diff.
>>
>> Any thoughts on this idea?
>>
>> Thanks,
>> Brian

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> This is not very typical conversion example, but is a BMW you're
> thinking about:
> http://www.evdrive.com/BMW_project/ProjectBMW.html

Incredibly well-planned - I'm guessing you had some hand in that? I
doubt there is anyone on the list not jealous of his project; it
should be very cool (and on the road before most pre-ordered Teslas).

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[quote]Brian Jeffries wrote:
> Group,
> I've been thinking for a while about converting a rear wheel drive vehicle.
> Specifically, I've been thinking of doing a BMW. The reasons for this are
> that it seems to me that since the vehicle has independent rear suspension
> and the dif is basically connected rigidly to the subframe, you could also
> mount an electric motor to the same subframe.
>
> This would allow doing away with the ICE motor, the transmission, and the
> driveshaft. Seems like it would be a good way to go IF I can find the right
> motor that operates in the proper rev range for being connected to the diff.

You need to find a slow turning, high torque, reversable motor for that.
Your average 15" tire is only turning around 800rpm at 60mph. EV motors
tend to be more comfortable at 4000 rpm.

So you could use a single speed gearbox that fits in place of the diff.
A couple possiblities of the latter are the MES 200 with its matching
Cararro 8.64:1 gearbox:

http://www.metricmind.com/data/ac_induction_motors_carraro.pdf

or the Azure Dynamics AC24LS with its AT1200 gearbox:

http://www.azuredynamics.com/products/force-drive/documents/AC24LS_DMOC445ProductSheet.pdf

Another possibility is to keep the diff and attach a large motor
directly to it. Most diffs are in the 3:1 to 4:1 range. Higher is
generally better. Ian Hooper is doing that with his EV Miata using an
11" Netgain WarP motor:

http://www.evalbum.com/1651

The Netgain TransWarP 9 or 11 are set up for that scenario with an
included tailshaft.

--Rick








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[quote]xxx@xxx.xxx wrote:

>> This is not very typical conversion example, but is a BMW you're
>> thinking about:
>> http://www.evdrive.com/BMW_project/ProjectBMW.html
>
> Incredibly well-planned - I'm guessing you had some hand in that?

This is indeed outstanding conversion planned. The owner is
my customer and all the components are top end, but this
is entirely his own design and execution. I expect it outperform
many EVs out there. Will check this out on PIR.

> I doubt there is anyone on the list not jealous of his project; it
> should be very cool (and on the road before most pre-ordered Teslas).

Well, I'm not jealous as working on something "double" of that:
http://www.metricmind.com/audi/main.htm :-)

While our machines are sophisticated by amateur standards, there
is technically nothing really spectacular in them. Just as you say, good
planning, thorough home work and professional engineering execution.
Bob is much better than me regarding machining, welding and this sort
of things, so I'm sure his creation will be no less impressive
than mine. There are few others out there to impress even more.
Stay tuned.

--
Victor
'91 ACRX - something different


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>
> Another possibility is to keep the diff and attach a large motor
> directly to it. Most diffs are in the 3:1 to 4:1 range. Higher is
> generally better. Ian Hooper is doing that with his EV Miata using an
> 11" Netgain WarP motor:
>
> http://www.evalbum.com/1651
>
> The Netgain TransWarP 9 or 11 are set up for that scenario with an
> included tailshaft.
>
>
Thanks - the Miata example is perfect. My thought had been to keep the
diff, and use the car primarily as a city car. So high speed acceleration
is not that big of a deal. One of the cool things about this set up is that
BMW used similar diffs over a long model range, so a solution that works
with one will get me close on several other models as well.


--
Brian Jeffries
xxx@xxx.xxx
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