# [EVDL] Anyone convert an Audi TT to EV?



## EVDL List (Jul 27, 2007)

Hi Everyone,

Checked the archive and saw nothing related. 

Has anyone considered, converted or got some ideas on converting an Audi TT (not Quattro) to EV ?
Anything of considerable of importance a first-time EV Converter should be aware of with this vehicle ? 

Arnold in Hershey, PA



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## EVDL List (Jul 27, 2007)

I'm doing an Audi A4. Not sure if the transmission pattern is the 
same. I used a WarP 11 which required modifying the subframe. A WarP 
9 would have fit without mods. Again, not sure how similar the A4 is 
to the TT.




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> > Hi Everyone,
> ...


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## EVDL List (Jul 27, 2007)

Try looking into a hub motor system. No drive line at all. More room for batteries and can make it either front or rear wheel drive. 




> [email protected] wrote:
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> > Hi Everyone,
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## EVDL List (Jul 27, 2007)

-----Original Message----- 
From: Al Swackhammer
Subject: Re: [EVDL] Anyone convert an Audi TT to EV?

> Try looking into a hub motor system. No drive line at all. More room for 
> batteries and can make it either front or rear wheel drive.

I'm not sure that would work so well. A TT is a relatively small, so there 
won't be much room for heavy batteries. A large mass of batteries would be 
necessary to combat the unsprung mass of a hub motor system. This of course 
wouldn't apply for very light hub motors, but those don't deliver much 
torque.

For an ideal ride the sprung weight/unsprung mass ratio* should be infinite. 
Each increase in the unsprung weight (weight of wheels, tires, brakes, half 
the suspension, etc) needs to be accompanied by a large increase in the 
sprung weight (body, occupants, engine, half the suspension, etc). This is 
why your EV rides better than your ICE on the same springs. Normally in an 
electric vehicle there is a large weight of sprung weight from the 
batteries, but in a relatively small vehicle like the TT there won't be as 
much battery mass. With hubmotors it is impossible not to increase unsprung 
mass, the only way to combat the effects would be to increase the sprung 
weight. Assuming you will be traveling at reasonable speeds aerodynamic 
weight will be limited to relatively small amounts.

This is also the reason the oft-quoted, rarely observed Civic on 24s goes 
flying. The unsprung weight is thrown in the air, F=MA, all that force hits 
the lightweight civic and its the difference between being hit by a jelly 
bean and a baseball bat. All the spring can do is extend the timeframe of 
the impact, but negate it (softer springs extend the timeframe).

So if you want a slow vehicle, the light-weight hub motors won't add too 
much weight, but for high power hubmotors you need a very large battery 
weight to combat the losses. I don't think the TT will hold enough batteries 
for this.
Joe




* This is one of those places where the difference between weight and mass 
matters. The vehicle force is Vehicle Mass * Gravitational Acceleration, 
this is weight. The unsprung force is Unsprung Mass * Impact Acceleration. 
The Gravitational Acceleration is approximately constant on earth (small 
variations depending on how far above sea level are ignorable). The Impact 
Acceleration depends on the road conditions are varies constantly. 

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## EVDL List (Jul 27, 2007)

This overstates the case. A solid axle car has about twice the unsprung weight 
of an IRS car! I'll bet most folks couldn't tell the difference between a solid 
axle Mustang and an IRS Mustang even if they drove them back-to-back. Likewise 
most people can't tell the difference between independent front suspension and 
solid axle for 4WD trucks, despite a huge difference in unsprung weight.

Mini Cooper racers can lose 35 lbs per tire by going to lightweight rims and 
lighter tires! If you could do your hub motor package for 35 lbs you'd have the 
same handling and ride as stock! The Mini Cooper is renown for its handling and 
popular for racing, despite having fairly high unsprung weight (run flat tires 
are heavy).

Yes, less unsprung weight handles and rides better -- so if you are going for 
that extra fraction of a second in racing around corners it's a worthy 
consideration. If you are paying major $$ for a car it's worthy. For most folks, 
though (racers included) adding 30 to 50 lbs per wheel can be a worthy 
compromise for handling and ride vs. cost, or off-road toughness, or drag racing 
toughness.

Now there are other reasons that make hub motors an unpopular choice. 
Off-the-shelf solutions are very expensive. They would be hard to protect in 
deep puddles. The brakes would transfer ruinous amounts of heat into the hub 
motor.

It would be better to use the tranny, or mount the electric motors similar to 
the original motor mounting, and drive the axles though speed reducers.



________________________________
From: Joseph Ashwood <[email protected]>
To: Electric Vehicle Discussion List <[email protected]>
Sent: Mon, November 1, 2010 10:05:48 PM
Subject: Re: [EVDL] Anyone convert an Audi TT to EV?

-----Original Message----- 
From: Al Swackhammer
Subject: Re: [EVDL] Anyone convert an Audi TT to EV?

> Try looking into a hub motor system. No drive line at all. More room for 
> batteries and can make it either front or rear wheel drive.

I'm not sure that would work so well. A TT is a relatively small, so there 
won't be much room for heavy batteries. A large mass of batteries would be 
necessary to combat the unsprung mass of a hub motor system. This of course 
wouldn't apply for very light hub motors, but those don't deliver much 
torque.

For an ideal ride the sprung weight/unsprung mass ratio* should be infinite. 
Each increase in the unsprung weight (weight of wheels, tires, brakes, half 
the suspension, etc) needs to be accompanied by a large increase in the 
sprung weight (body, occupants, engine, half the suspension, etc). This is 
why your EV rides better than your ICE on the same springs. Normally in an 
electric vehicle there is a large weight of sprung weight from the 
batteries, but in a relatively small vehicle like the TT there won't be as 
much battery mass. With hubmotors it is impossible not to increase unsprung 
mass, the only way to combat the effects would be to increase the sprung 
weight. Assuming you will be traveling at reasonable speeds aerodynamic 
weight will be limited to relatively small amounts.

This is also the reason the oft-quoted, rarely observed Civic on 24s goes 
flying. The unsprung weight is thrown in the air, F=MA, all that force hits 
the lightweight civic and its the difference between being hit by a jelly 
bean and a baseball bat. All the spring can do is extend the timeframe of 
the impact, but negate it (softer springs extend the timeframe).

So if you want a slow vehicle, the light-weight hub motors won't add too 
much weight, but for high power hubmotors you need a very large battery 
weight to combat the losses. I don't think the TT will hold enough batteries 
for this.
Joe

* This is one of those places where the difference between weight and mass 
matters. The vehicle force is Vehicle Mass * Gravitational Acceleration, 
this is weight. The unsprung force is Unsprung Mass * Impact Acceleration. 
The Gravitational Acceleration is approximately constant on earth (small 
variations depending on how far above sea level are ignorable). The Impact 
Acceleration depends on the road conditions are varies constantly. 



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## EVDL List (Jul 27, 2007)

> [email protected] wrote:
> 
> >
> > Hi Everyone,
> ...


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## EVDL List (Jul 27, 2007)

Hi Arnold,
I believe that Mark Farver at Revolt is working on an Audi A8, and has made
signifignant progress on keeping the electronics and transmission functions
intact. Hope that this is helpful.
-Tom True



> <[email protected]> wrote:
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> >
> > Hi Everyone,
> ...


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