# Re: [EVDL] Motor coupler issues



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Motor coupler issues*

Matt,
Nice beef job on the shaft coupler.
http://www.jouleinjected.com/welded.jpg
If the shaft goes it won't be there ;-)

It looks like you filled in the pilot hole in the end of the shaft too. I'm thinking about machining a plug with a chamfer on it,
hammering it in and welding a bead around it. From this pic of your split DE shaft http://www.jouleinjected.com/cracked.jpg it
looks like it was due to weakness in the OD on the shaft due to the pilot bearing bore.

I'm thinking if I plug it and stiffen up the end I might be able to prevent that fatigue for a while. At least until Jim can
start stocking WarP9 shafts ;-) The pilot bore down the center of the (supposedly strong) drive shaft looks a little lacking in
the beef department, especially at the bottom of the key slot.
http://home.gci.net/~saintbernard/NetGain_WarP9_Hi_Torque_Electric_gear_coupler.jpg


Hey Jim, see what Kieth would charge to knock off some hardened, stock shape WarP9 shafts, only without the pilot bore in the DE.
That 1-1/8" shaft should be suufficient for a puny 'ol 500 ft-lbs. Its a shame its integrity is compromised by the pilot bore.
Or maybe see what his take is on just doing the plug and weld thing. Anything to give that key something to bite against on the
extreme end would no doubt help.

Mike,
Anchorage, Ak.

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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Motor coupler issues*



> --- Mike Willmon <[email protected]> wrote:
> 
> > Hey Jim, see what Kieth would charge to knock off
> > some hardened, stock shape WarP9 shafts, only
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Motor coupler issues*

Kinda sounds like we're trying to solve a problem that Jeep solved on axle 
shafts a while ago (and I think most makes solved earlier). Jeep axles used 
to have a separate flange on the end with a keyway and a nut. The joint was 
a reliability issue. I had the same problem with a stub axle on my Lotus. 
Jeep (actually Dana) made the flange and axle one piece on later Jeep axles.

Could we get axle shaft blanks from a custom axle manufacturer with a flange 
on the end and turn it down and use it for an armature shaft with a hefty 
output flange? That ought to solve hub failures. Just bolt a flywheel, 
U-joint flange, or whatever, to what would be the wheel mounting flange. I 
suppose it would make it pretty tough to assemble and dis-assemble the 
motor. The case end would have to go on before the shaft was put through 
the armature laminations, and bearing changes would be a bear. But I don't 
think you could break it, and it would save money on taper lock hubs.

Marty

----- Original Message ----- 
From: "Jim Husted" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Thursday, August 09, 2007 11:19 AM
Subject: Re: [EVDL] Motor coupler issues


>


> > --- Mike Willmon <[email protected]> wrote:
> >
> >> Hey Jim, see what Kieth would charge to knock off
> >> some hardened, stock shape WarP9 shafts, only
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Motor coupler issues*

Careful now or you'll be gettin' on Jim's evil twin (or triplets, or quadruplets) list. First one of us sends him a motor with a welded flange on the motor shaft might find the sharp side of that new hacksaw blade put to use ;-P

I don't think there is much trouble with the WarP9 shaft per se, just that little extra material in the right (or wrong) place that is bored out for th pilot bearing. I really don't think I'll have any problem with the stock WarP9 shaft I have in my truck. But I don't need to lift and carry the front end of my truck 60 feet with gut wrenching Hi-Torque launches. For stockers I think its more than OK.

Mike,
Anchorage, Ak.

----- Original Message -----
From: Marty Hewes <[email protected]>
Date: Thursday, August 9, 2007 11:43 am
Subject: Re: [EVDL] Motor coupler issues
To: Electric Vehicle Discussion List <[email protected]>

> Kinda sounds like we're trying to solve a problem that Jeep solved 
> on axle 
> shafts a while ago (and I think most makes solved earlier). Jeep 
> axles used 
> to have a separate flange on the end with a keyway and a nut. The 
> joint was 
> a reliability issue. I had the same problem with a stub axle on my 
> Lotus. 
> Jeep (actually Dana) made the flange and axle one piece on later 
> Jeep axles.
> 
> Could we get axle shaft blanks from a custom axle manufacturer with 
> a flange 
> on the end and turn it down and use it for an armature shaft with a 
> hefty 
> output flange? That ought to solve hub failures. Just bolt a 
> flywheel, 
> U-joint flange, or whatever, to what would be the wheel mounting 
> flange. I 
> suppose it would make it pretty tough to assemble and dis-assemble 
> the 
> motor. The case end would have to go on before the shaft was put 
> through 
> the armature laminations, and bearing changes would be a bear. But 
> I don't 
> think you could break it, and it would save money on taper lock hubs.
> 
> Marty
> 

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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Motor coupler issues*

No doubt the TransWarp9 is better built to take the abuse we are about to impart on it. My concern is more with the pilot hole in the end of the WarP9. I know you don't suspect that is a weak point, but after seeing the crack in Matt's DE shaft it looks like it started out on the end and propagated inward. That tells me that maybe filling that hole and stiffening it on the end would help. But if I'm wrong, I'll be hollering for a new one. I should see if George could provide replacement parts ala carte'. George if you're reading and extra WarP9 shaft on the shelf wouldn't hurt anything and someday one of us will need it ;-)

Mike,
Anhcorage, Ak.

----- Original Message -----
From: Jim Husted <[email protected]>
Date: Thursday, August 9, 2007 8:21 am
Subject: Re: [EVDL] Motor coupler issues
To: Electric Vehicle Discussion List <[email protected]>

> 


> > --- Mike Willmon <[email protected]> wrote:
> >
> > > Hey Jim, see what Kieth would charge to knock off
> > > some hardened, stock shape WarP9 shafts, only
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Motor coupler issues*



> --- Tim Humphrey <[email protected]> wrote:
> 
> > Here's an area I know nothing about....
> >
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Motor coupler issues*

Please keep in mind that launching a 4000lb beast at 1/2G (paltry) is
the same amount of torque at the motor as launching a 2000lb dragster at
1G(slow dragster, but you get the point)

F=MA: 4000lb*16ft/sec = 2000lb*32ft/sec

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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Motor coupler issues*



> --- Tim Humphrey <[email protected]> wrote:
> 
> > Here's an area I know nothing about....
> >
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Motor coupler issues*

Do you suppose motor coupler failures are more common on cars without a 
trans? With an overall gear reduction of 10 to 1 in first gear (trans and 
axle), the motor will only see 10% of the torque the axles see (compared to 
roughly 33% of it with only an axle). I won't attempt to figure out what 
the maximum torque would be at the axle before the tire spins, but only 10% 
of it would get back to the coupler in this case. I suppose once you hit 1 
to 1 in the trans, you'd be back to the roughly 33% number, but how many of 
us will be producing full motor current and torque once the motor RPMs are 
coming up? Sounds like if you are running a trans, attempting to pass a 
truck on the freeway in top gear is where the coupler is heavily loaded, not 
during a tire smoking launch in first. Am I on track here?

Marty

----- Original Message ----- 
From: "Jeff Shanab" <[email protected]>
To: <[email protected]>
Sent: Saturday, August 11, 2007 10:11 AM
Subject: Re: [EVDL] Motor coupler issues


> Please keep in mind that launching a 4000lb beast at 1/2G (paltry) is
> the same amount of torque at the motor as launching a 2000lb dragster at
> 1G(slow dragster, but you get the point)
>
> F=MA: 4000lb*16ft/sec = 2000lb*32ft/sec
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>
> 


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Motor coupler issues*

The motor armature and associated drivetrain constitute a second order 
ocillatory mechanical system. The armature has a high moment of inertia and 
is coupled via a "spring" which is the drive train. Any step applications 
of torque will cause torque overshoot, up to a doubling of the intended 
torque. This factor has always caused high stresses in electric motor 
propulsion and has led to surprise failures of couplings, drive shafts, 
motor mounts, etc, when this is overlooked. 

You may say that step torque applications don't occur in well designed 
electric propulsion, but spinning tires on a crosswalk stipe, and then 
hitting good pavement is an example. 

Also, drive train components do not necessarily break right away, but can 
fatigue slowly and weaken, eventually breaking.








On Sat, 11 Aug 2007 11:02:17 -0500, Marty Hewes wrote
> Do you suppose motor coupler failures are more common on cars 
> without a trans? With an overall gear reduction of 10 to 1 in first 
> gear (trans and axle), the motor will only see 10% of the torque the 
> axles see (compared to roughly 33% of it with only an axle). I 
> won't attempt to figure out what the maximum torque would be at the 
> axle before the tire spins, but only 10% of it would get back to the 
> coupler in this case. I suppose once you hit 1 to 1 in the trans, 
> you'd be back to the roughly 33% number, but how many of us will be 
> producing full motor current and torque once the motor RPMs are 
> coming up? Sounds like if you are running a trans, attempting to 
> pass a truck on the freeway in top gear is where the coupler is 
> heavily loaded, not during a tire smoking launch in first. Am I on 
> track here?
> 
> Marty
> 
> ----- Original Message ----- 
> From: "Jeff Shanab" <[email protected]>
> To: <[email protected]>
> Sent: Saturday, August 11, 2007 10:11 AM
> Subject: Re: [EVDL] Motor coupler issues
> 
> > Please keep in mind that launching a 4000lb beast at 1/2G (paltry) is
> > the same amount of torque at the motor as launching a 2000lb dragster at
> > 1G(slow dragster, but you get the point)
> >
> > F=MA: 4000lb*16ft/sec = 2000lb*32ft/sec
> >
> > _______________________________________________
> > For subscription options, see
> > http://lists.sjsu.edu/mailman/listinfo/ev
> >
> >
> 
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev

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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Motor coupler issues*

Interesting. So what you're saying is that due to elasticity in the drive 
system, the drivetrain can wind up, resulting in maybe twice the normal 
torque load if, for example, the tires slip, then stick? Seems to make 
sense logically. How does this impact the idea of using a rubber donut in 
the driveshaft, or a spring equipped clutch hub, or even higher profile 
tires to absorb shocks? Sounds like it may actually make the torque peaks 
higher by maybe reducing resonant frequency and allowing more wind-up 
amplitude, or does it just change the frequency of oscillation? Would 
increasing frequency or stiffness push the shock energy back to the contact 
patch and battery instead of storing and releasing it, or does the shock 
wave do a fixed end reflection when it hits the momentum of the armature and 
oscillate until something dampens it out anyway? What is the implication to 
the drivetrain design? I suppose the answer is complex.

Marty
----- Original Message ----- 
From: "George Swartz" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Saturday, August 11, 2007 11:29 AM
Subject: Re: [EVDL] Motor coupler issues


> The motor armature and associated drivetrain constitute a second order
> ocillatory mechanical system. The armature has a high moment of inertia 
> and
> is coupled via a "spring" which is the drive train. Any step applications
> of torque will cause torque overshoot, up to a doubling of the intended
> torque. This factor has always caused high stresses in electric motor
> propulsion and has led to surprise failures of couplings, drive shafts,
> motor mounts, etc, when this is overlooked.
>
> You may say that step torque applications don't occur in well designed
> electric propulsion, but spinning tires on a crosswalk stipe, and then
> hitting good pavement is an example.
>
> Also, drive train components do not necessarily break right away, but can
> fatigue slowly and weaken, eventually breaking.


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