[mattW]

You will need friction brakes on at least 2 wheels. Regen isn't very effective at low rpm and not at all when parked.

[unclematt]

Originally Posted by mattW

You will need friction brakes on at least 2 wheels. Regen isn't very effective at low rpm and not at all when parked.

Thats not what PML Flightlink is reporting they found in their wheel motor development. They use ZERO friction brakes, and have zero problems. You can find this on their site being used on their mini-cooper, and also the Lightning is being sold in Britain using their wheel motors, which have no friction brakes whatsoever.

[mattW]

Wow that's pretty impressive. I was just linking them for a concept not to buy them, I'd be pretty impressed if this idea gets off the ground i.e. the open source version.

[unclematt]

Originally Posted by mattW

Wow that's pretty impressive. I was just linking them for a concept not to buy them, I'd be pretty impressed if this idea gets off the ground i.e. the open source version.

Their concept is brilliant, I agree. And you may be correct that we have to use them in an open source design. Only time will tell how successful this project will be, or if we will come to the conclusion that friction brakes are required (maybe even as a parking /emergency brake).

[JRK5150]

The debate on brakes with this project is valid for both sides. I see pure electric regen. brakes as fine for all but stopping, parking, and possibly extremely low speed. The simplest solution I can come up with is to incorporate provisions for mounting a small mechanical braking system into the design of the wheel motor. This way, brakes could be added to the rear wheels for stopping and parking while using electric brakes to handle the rest. The problem with allowing the electric brakes to hold the car when stopped or parked, which they could theoretically do, is that the motors would be taking power even when not in motion. It seems to me that the minuscule weight gain of two small discs or drums would out-weigh the power losses of parked electric brakes in the long run. The front brakes wouldn't need any sort of mechanical brakes though!

[mattW]

I just had a thought that we could put 'skid steer' as one of the options for the controller i.e. right hand side wheels to move forward and left hand to move back. Then you can turn on less than a dime just like a tank... lol wouldn't do the tyres much good but would be amazing on narrow streets for U turns!

[JRK5150]

HA! What the heck! As long as it was a programming option, some folks might find it useful!

[Manntis]

Originally Posted by unclematt

The whole "unsprung weight" issue is overblown in my opinion. Yes, we should design them as light as possible, but in my research I have found that most manufacturers found that when much of the weight is removed that is associated with the regualr drivetrain that the wheel motor ends up weighing only slightly more by comparison. I am NOT interested in mounting motors to shafts. That defeats part of the purpose of doing wheel motors in the first place.

The regular drivetrain weight isn't unsprung weight, it's weight suspended. Unsprung weight refers specifically to the weight of items not suspended, i.e. the wheel rims, tires, hubs, and brakes (with the exception of inboard IRS systems such as Jaguar's original disc configuration)

Using a wheel motor is an increase in unsprung weight. Removing the stock ICE, transmission, radiator, etc. is removing sprung weight. Two different things when it comes to the physics of how various bits of the vehicle move in relation to each other.

[JRK5150]

While it is true that removing the engine and transmission will not effect the unsprung weight, electric wheel motors can eliminate the need for lots of other weighty pieces. On most rear wheel drive vehicles, the weight of the entire differential/rear end housing is unsprung. So is the braking assembly and half the weight of the drive shaft and half the weight of any control arms. This alone could more than offset the weight of a properly designed wheel motor. For front wheel drive and IRS equipped vehicles, the brake assemblies, hub/steering knuckle assemblies, and half the weight of the half shafts could either be eliminated or drastically reduced in size and weight depending on the design of the wheel motor. Here again, the unsprung weight issue isn't problematic as long as the design of the wheel motor is kept as light as possible. The biggest problem I see is in the front suspensions of rear wheel drive vehicles or the rear suspensions of front wheel drive vehicles. Here, the only weight to be eliminated would typically be the knuckle/hub assembly and some brake components. Even in this case, though, the weight increase of a wheel motor over the removed components would be minimal as far as I can tell. I think it would be possible to all but eliminate any minor weight gain by using a lighter weight aftermarket wheel and tire combination. I think, through proper engineering, the unsprung weight debate will be a virtual non-issue.

[unclematt]

Originally Posted by mattW

I just had a thought that we could put 'skid steer' as one of the options for the controller i.e. right hand side wheels to move forward and left hand to move back. Then you can turn on less than a dime just like a tank... lol wouldn't do the tyres much good but would be amazing on narrow streets for U turns!

This would make parking much easier as well...

On the subject of motor form, we have a suggestion of an AC induction motor, and I wonder about a large brushless DC motor. Maybe we should discuss and toss around the benefits and drawbacks to both. Then we can start to talk about motor construction.

On the controller and software front, I must admit I have less expertise in this are than any other. I liked the suggestion made about a test bed that was simple and easy to build to test our prototype controllers. Is someone willing to take on this part of the project and run with it as a general coordinator/facilitator?