# Rigid or Flexible coupling for Motor-to-Tranny connection?



## etischer (Jun 16, 2008)

that is the motor side.











that is the tranny side. 

Now do I go with this option:









Or this option?










The rigid coupler will be cheaper and more reliable, but will require a very accurate alignment of both motor shafts. 

The flex coupling will provide isolation from vibration and allow for some misalignment. I suspect it will have the feel of the dual mass flywheel that my Audi has. The coupling may also introduce vibraion, but it is not supporting any weight like it typically would on the end of a driveshaft.

I beleive my clutch disc is from a dual mass flywheel setup because it doesn't have any springs in it.


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## Twilly (Jan 22, 2008)

I went with a solid coupling, and vibration is not a issue with an electric motor


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## etischer (Jun 16, 2008)

I haven't seen anyone with a flexible coupling, im wondering if it would be an advantage. Primarily in clunking when accelerating and decelerating, and going over rough roads. It would maybe make the car more refined? 

Are the springs in a clutch only used to reduce chatter? 

Im planning on making the adapter plate myself, so not sure how hard it is to align the motor and tranny shaft. I was thinking a little flex would be good.


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## kittydog42 (Sep 18, 2007)

If you make your own adapter plate, make sure the dowel pins on the bell housing line up exactly. That is what keeps the alignment of the motor and transmission shaft free from binding. Even if a flex coupling is used, you should not look for it to make up that difference. Those dowel pins are the only holes that have to be exact, other than the center point of the shafts.


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## Twilly (Jan 22, 2008)

etischer said:


> I haven't seen anyone with a flexible coupling, im wondering if it would be an advantage. Primarily in clunking when accelerating and decelerating, and going over rough roads. It would maybe make the car more refined?
> 
> Are the springs in a clutch only used to reduce chatter?
> 
> Im planning on making the adapter plate myself, so not sure how hard it is to align the motor and tranny shaft. I was thinking a little flex would be good.


The Motor and trans should be mounted as one and any motion should effect both as one unit...No clunking when going over rough roads.

The springs are these to reduce the pulsation of the ICE, but there is no pulsing in a electric motor.


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## Bugzuki (Jan 15, 2008)

I would go with the solid coupling. As said before the springs are there to make the clutch engagement smoother with the ICE. The rotation of the electric motor is smooth and does not have the vibration that the ICE has from combustion.

Side question. In those pictures is that a Ford Ranger motor? If it is what spline size does it have - or how does that coupling work?


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## etischer (Jun 16, 2008)

Yep, thats the ranger motor. The output is a gear, not a splined shaft. From tooth tip-to-tip it is 1.75", from root-to-root it is 1.5. The ID is 1.25". 

The coupling is a taper lock. There are four pieces, Im only using three. There is a split tapered ring which slides on the motor shaft. There are two tapered rings with the bolt pattern you see, they clamp on the split ring. The split ring contracts onto the motor shaft. It works the same as a collet/mandrel on a dremel. Im using the 1 3/4 part listed below














Bugzuki said:


> I would go with the solid coupling. As said before the springs are there to make the clutch engagement smoother with the ICE. The rotation of the electric motor is smooth and does not have the vibration that the ICE has from combustion.
> 
> Side question. In those pictures is that a Ford Ranger motor? If it is what spline size does it have - or how does that coupling work?


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## chamilun (Jun 17, 2008)

etischer,
can you detail a bit more how you made your coupling/adapter. it looks like you used some non-custom parts (?)

thanks!


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## etischer (Jun 16, 2008)

The coupler is going to be a custom part. The taper lock fitting is off the shelf. The flexible coupler,which I decided not to use, uses a standard rotoflex coupler found on most european rear wheel drive cars. They use the rotoflex instead of u-joints on driveshafts.


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## Twilly (Jan 22, 2008)

Are you sure you will have enough surface area for the device to lock on to the shaft since it is a geared shaft vs a solid shaft? There is a ton of HP on that connection


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## Bugzuki (Jan 15, 2008)

Are you going to keep the flywheel, clutch and pressure plate? With that ridged spacer it looks like it will take up all the room for the Clutch setup, and would move the Flywheel a long way away from the motor. 

Then the spacer attaches with 3 bolts and the other holes fit around the coupler bolts - right?

I also have a Ranger motor.


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## etischer (Jun 16, 2008)

Im eliminating the clutch. The AC motor is constant torque from 0-3500 rpm, and constant horsepower from 3500-11k. Most AC systems don't do gear changes.

If I do want to do gear changes, I can line shaft the motor speed to the wheel speed with the gear ratio of the gear I want to shift into, in effect "electric synchro" shifting. 

Another option is if I just have 2nd gear and 4th gear. I know the rpm of 4th will be half the rpm in 2nd. before shifting from 2nd to neutral, I can store the current motor speed, go into neutral, then multiply the memorized motor speed by 50%. Once the motor has reached that speed, I can run low torque, and shift into gear. The transmissions synchros won't have to do too much speed to match rpms. 


The coupler will bolt on the taperlock using 9 bolts. I will use 6 bolts and 3 dowels on the clutch side. 

What is your ranger motor going into! Good to see Im not the only one!



Bugzuki said:


> Are you going to keep the flywheel, clutch and pressure plate? With that ridged spacer it looks like it will take up all the room for the Clutch setup, and would move the Flywheel a long way away from the motor.
> 
> Then the spacer attaches with 3 bolts and the other holes fit around the coupler bolts - right?
> 
> ...


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## Bugzuki (Jan 15, 2008)

etischer said:


> Im eliminating the clutch. The AC motor is constant torque from 0-3500 rpm, and constant horsepower from 3500-11k. Most AC systems don't do gear changes.
> 
> The coupler will bolt on the taperlock using 9 bolts. I will use 6 bolts and 3 dowels on the clutch side.


Are you leaving the clutch disc in and taking everything else out? Is that so you can use the splines in the disc? Can you cut off the parts of the clutch you will not be using (less rotating mass)?



etischer said:


> What is your ranger motor going into! Good to see Im not the only one!


I have a wrecked 2005 Scion tC i am rebuilding and hope to make electric. What model Audi are you using? Madmac also has a ranger motor. He is in the UK.


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## etischer (Jun 16, 2008)

Looks like a nice car to convert. Im converting a 2001 Passat. Its on the heavy side, but I wanted something I would actually want to drive =)

http://etischer.com/awdev/




Bugzuki said:


> Are you leaving the clutch disc in and taking everything else out? Is that so you can use the splines in the disc? Can you cut off the parts of the clutch you will not be using (less rotating mass)?
> 
> 
> [/IMG]


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## Bugzuki (Jan 15, 2008)

That is also a very nice car. I have always like the Passat.

What bearings part number did you use to replace the OEM bearings on the motor? I would have totally missed that.

Sorry to hijack your thread, but you already made your coupling descission.


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## etischer (Jun 16, 2008)

SKF SKF 6209 2Z/C3

6209 is the size

2Z means 2 sided metal shields

C3 is the clearance I believe. The original bearing was C4, the guy who said I should change the bearings said he used a C3 clearance, so I just did the same. Was 100 bucks for both bearings.


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## Bugzuki (Jan 15, 2008)

Thanks for the information.


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## major (Apr 4, 2008)

etischer said:


> SKF SKF 6209 2Z/C3
> 
> 6209 is the size
> 
> 2Z means 2 sided metal shields.


Hi etischer,

Looks like you're doing a bang up job. Well documented on the web site. Thought I'd throw a few comments your way.

I'd have gone with seals on the bearings. When they get hot, the grease will liquefy and run out. Eventually you'll be running dry bearings. I'd recommend high temp grease and high temp seals, both sides. A little more drag, but worth it in bearing life.

Those are probably current transformers on the circuit card. If you can get to the spec, you can replace them with higher amp versions. 

Look up the specs on the IBGT modules. I think you need to gate those at -8V for off and +15 volts for on. Specs will tell you how fast you need to deliver gate charge. The small drive board probably won't handle those large modules. Maybe you can get a driver board from a 50 kW unit, or stand alone gate drivers.

And I didn't see a feedback device on the motor (encoder or resolver). I think you'll need one.

Regards,

major


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## etischer (Jun 16, 2008)

Well, its the torque, not hp that matters in terms of slip. Friction force = normal force * Coeff. of friction, there's no surface area in the equation. I am applying more pressure (force/area) to the teeth, and they might crack, that is what Im worried about. I don't think the taperlock will slip. 



Twilly said:


> Are you sure you will have enough surface area for the device to lock on to the shaft since it is a geared shaft vs a solid shaft? There is a ton of HP on that connection


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