# Transmission vs series/parallel



## MalcolmB (Jun 10, 2008)

Hi Telco
The same questions have been buzzing around my head for a while. I don't have any solid answers, but I've already got a pair of 7" motors so I'm going to try series/parallel switching to see how it works out. You're right about running motors in series for low-speed torque and in parallel for more speed. All the conversions I've come across that use this system have been drag racers, but I don't see why it shouldn't work well for an everyday runabout. The main advantages I see are that you eliminate the weight of the gearbox and differential (by using chain/belt drive to each front wheel independently). It also seems more elegant somehow to spread the torque band electrically rather than mechanically. By using two small motors instead of one big one it should be easier to keep them cool too.

Disadvantages include the increased number of contactors and complexity of wiring. It hurts my head working out the best arrangement for series/parallel switching and reversing. I expect having two sets of brushes will mean slightly greater losses as well.

I've no idea about the the last part of your question, but I'd like to know too.


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## enganear (Jun 16, 2008)

Using two motors with series / parallel switching based on rpm should work even better with a transmission. It is my understanding that the Zilla controller allows for a programmed rpm switch point.

I was considering 2 Impulse 9 motors for my Mustang, but I am currently favoring the WARP11 for range, power and simplicity of mounting.

What the EV builder really needs is a siamesed 9" in one housing with dual external connections.
-enganear


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## VDubber (Jun 2, 2008)

enganear said:


> Using two motors with series / parallel switching based on rpm should work even better with a transmission. It is my understanding that the Zilla controller allows for a programmed rpm switch point.
> 
> I was considering 2 Impulse 9 motors for my Mustang, but I am currently favoring the WARP11 for range, power and simplicity of mounting.
> 
> ...


Jim Husted can actually make that for you (a siamesed motor) - check out his site:

http://www.hitorqueelectric.com/

http://hitorqueelectric.com/gallery/v/custom_motors/Siamese9/


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## enganear (Jun 16, 2008)

VDubber said:


> Jim Husted can actually make that for you (a siamesed motor) - check out his site:
> 
> http://www.hitorqueelectric.com/
> 
> http://hitorqueelectric.com/gallery/v/custom_motors/Siamese9/


Thanks for the links, I'll have to reconsider this option in comparison with the WARP11. I would still use a transmission.....
-enganear


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## joseph3354 (Apr 2, 2008)

netgain is building a special motor called "Jimpulse 9" it is a siamesed motor.cost over 5k because it is a special order.apparently being built by jim husted according to the website.you can check it out here:

http://www.go-ev.com/End_User_Pricing.html


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## Telco (Jun 28, 2008)

Thanks folks. It was the drag racers that got me wondering about this, considering they had a hard enough shift to break the tires loose on the S-P shift. 

If I were to go with the 2 motor option instead of the one motor/transmission option, that siamesed job would be the way to go from what I read about it. One common high speed balanced shaft would be way better than a coupling between the two.

On the other hand, the battery draw for one larger motor with a 3 speed transmission should be less. This is an important consideration as well. If I do this I'll be going as a diesel electric setup, not a hybrid, ie there will be no physical connection between the ICE and the wheels. 

Any more opinions on this?


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## MalcolmB (Jun 10, 2008)

Are there any potential problems with siamesing motors by mounting them side by side using a chain drive to couple the shafts? This would avoid alignment problems, although a chain drive might be a bit noisy at around 5,000 rpm. The motors could then be mounted transversely and used to drive a chain drive differential like this: http://www.quaife.co.uk/Chain-drive-cars-ATB-differential 

I'm still tempted by the idea of using a motor to drive each drive wheel (front or rear) independently with a chain drive. In series the motors share the load so they work together like a differential, and in parallel they act as a limited slip differential: http://www.4qd.co.uk/faq/bmnc2.html#diff

From what I've read about the Zilla it does series/parallel switching under load, so you get a real kick on switchover. That's good for drag racing and would impress your passengers  but I'd like to be able to switch manually. There are some situations where you just don't want a sudden burst of torque. A paddle-activated manual gearchange on the steering wheel would be cool...


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## enganear (Jun 16, 2008)

MalcolmB said:


> Are there any potential problems with siamesing motors by mounting them side by side using a chain drive to couple the shafts? This would avoid alignment problems, although a chain drive might be a bit noisy at around 5,000 rpm. The motors could then be mounted transversely and used to drive a chain drive differential like this: http://www.quaife.co.uk/Chain-drive-cars-ATB-differential
> 
> I'm still tempted by the idea of using a motor to drive each drive wheel (front or rear) independently with a chain drive. In series the motors share the load so they work together like a differential, and in parallel they act as a limited slip differential: http://www.4qd.co.uk/faq/bmnc2.html#diff
> 
> From what I've read about the Zilla it does series/parallel switching under load, so you get a real kick on switchover. That's good for drag racing and would impress your passengers  but I'd like to be able to switch manually. There are some situations where you just don't want a sudden burst of torque. A paddle-activated manual gearchange on the steering wheel would be cool...


IMHO, timing belt would be a much better choice than chain for coupling the motors together if you cannot direct couple them.
-enganear


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## kixGas (May 2, 2008)

I have put some thought into this and haven't decided which way I am going to go. I would not eliminate the differential for 2 reasons: 1) you would likely not have enough gearing to get moving from a dead stop. Don't forget that most differentials are roughly a 3:1 ratio. 2)when turning the left and right wheels turn at different speeds. With one motor driving each wheel you would either need a sophisticated controller or have a car that does a good job at going straight- and nothing else.
Also I wouldn't do a chain drive. A sequential belt would be a better option. They are generally more durable, quiet, and self aligning. If I were to go transmission-less and couldn't afford one of Jim Husted's masterpieces I would do two motors side by side with an equal size sequential gear on each one. Have the two motors mounted above the differential of an IRS (the diff doesn't move with the suspension) and have a larger sequential gear mounted to the diff. throw a belt on and you are good to go.

o---o
\ /
\O/


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## Hi Torque Electric (Dec 23, 2007)

Hey all

As to the Jimpulse9’s (George Hamstra nicknamed them Jimpulse9’s as they’re made using two Impulse9’s ) I’ll be shipping the first ones out here soon 8^) That said, I’ll have some better data on the who DD vs tranny hopefully soon. Like most of what I do these are born from requests (I bet you all thought I was the sicko)(but in fact it’s all of you guys who ask me to do it that are the root of my Evil 8^o I think in many ways, this is one of those “one mans poison is another mans hunny” kind of things in that it’s not something I’d advise for everyone. In general, it takes twice the motor and twice the controller to do a direct drive.

As to the double barrel shotgun approach this has been done and is how Otmar’s California Poppie motor’s setup. In fact I’ve been wanting to throw my hand into that aspect myself as there are aspects to it worth merit to do it that way, but I also feel there’s cons as well but as of yet people are asking for in-line single barreled shotguns 8^o Maybe it’s the Wayland’s got one (and mines Even bigger) cool factor. 

There were a number of factors in choosing the Impulse9 as a base in that the finished unit is a ½” “shorter” than John’s Siamese8, the armatures are keyed (for good arm to shaft interfacing), and the brush to commutator footprint is larger than the Advance counterpart, along with a slue of other reasons. In dealing with a DD setup there’s a serious advantage in using twin smaller motor (regardless how they’re coupled) in that you get twice the commutation vs using a single larger motor. Taking the Warp11 motor (225lbs) as was quoted by someone what will be found is that the single 11 has just 8 brushes to chug amps with compared to 16 if using dual Impulse9’s (250ish) (same sized brushes as well). I’m also beginning to feel as if the larger diameter motors are a bit like lumbering giants compared to the smaller rotational mass of the smaller motors (at least for those looking for all the zip they can get 8^)

Anyway, hopefully this adds a bit of insight into my madass world 8^o so you better watch out for the half inverted funk Monkey that just might be invading your local streets as they’re coming

Jim Husted
Hi-Torque Electric


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