Crazy Idea

[JFerguson]

Has anybody considered putting regenerative brakes on an AS? Last year GMC released the Sierra truck as a hybrid. The brakes for that vehicle might be able to fit an Airstream. I just think it might be interesting to charge your batteries every time you tap the brakes.

If I am just completely off my nut for thinking about this let me know.

[wmarsha]

Wow, that's a great idea! I was thinking about putting disc brakes on the AS instead of rebuilding-now I am thinking regen brakes, 'course the cost will probably kill the idea.

[Beginner]

Ok so take it one more step.
If you pur regenerative brakes on the AS, why cant you also use them as dynamic brakes as on a Diesel Locomotive?
Beginner

[Minno]

Originally Posted by Beginner

If you pur regenerative brakes on the AS, why cant you also use them as dynamic brakes as on a Diesel Locomotive?
Beginner

Regenerative brakes and Dynamic brakes rely on some of the same basic principles, where they will use the resistance of a “generator” to provide braking force instead of the friction of brake pads and shoes. What you do with the electricity generated by the braking force is where they are different. Regenerative brakes on a hybrid or electric car use that electricity to recharge the batteries. Dynamic brakes on the other hand, simply dump that electricity into honking big resistors to slow the train. They produce a fair amount of waste heat, but do not wear out like a friction pad would. Not used to recharge batteries much if at all. There are a few more significant differences, but those are the basic principles.

Chris

[JFerguson]

Wow..so the idea has some merit. I thought you all were gonna run me off as a crazy. I wonder how you go about obtaining regen breaks.

[Minno]

Oh, every idea has merit! It's just a question of how much money you'll want to throw at it, let alone finding the parts to do it.

[JFerguson]

You're right Chris that's the hard part. At least hard for now but I suspect as hybrids become increasingly popular and mainstream that parts will get cheaper and more abundant.

[Aviator]

Start looking for wrecked Sierra's.

[snake]

It's not the brakes that do the regeneration, it's the drive train and electric motor, which also acts as a generator.

Of course the vehicle needs to have conventional brakes too, since more braking can be needed then the regenerative process will produce.

[Beginner]

I was unsure if the electricity produced was "burned off" by resistors or if reverse polarity Electricity was gradually fed to the drive/generator motor trying to reverse it.
However I'm not really sure if regenerative braking would be really pratical on a car as at some point you would be producing to much energy (voltage level goes to high for batteries) or heat becomes too great for the motor.
The long pole in the tent though is money.
Beginner

[markdoane]

I think the more practical problem with diesel locomotives is economics. You would need a really big honking set of batteries to store all that energy that is now being thrown off in the resistors. And they would really only be useful on those long downhill runs out west. Otherwise they are like regenerative brakes on a car - pretty useless when you're cruising the interstate, only useful in stop and go city traffic.

Same reason they work so well on city buses, not so good on interstate trucks.

[Jammer]

Originally Posted by JFerguson

Has anybody considered putting regenerative brakes on an AS? Last year GMC released the Sierra truck as a hybrid. The brakes for that vehicle might be able to fit an Airstream. I just think it might be interesting to charge your batteries every time you tap the brakes.

If I am just completely off my nut for thinking about this let me know.

The Sierra regenerative braking works using a motor-generator between the engine and the transmission.

It would work fine on an Airstream if you're willing to retrofit a suitable drive train less engine. For braking on both axles you'd want a twin screw setup, and a 4L60e transmission out of the Sierra, and the motor-generator. Then it's simply a matter of some controls and programming.

In general, traction motors are too heavy to be placed on the axle except for rail applications because the unsprung weight goes way too high, so the obvious solution of a planetary gear unit and a motor/generator on the axle won't work. That leaves the standard possibilities of either a solid axle (cheap but heavy) or a full-floating setup with independent shafts to a center diff or maybe to a planetary and m-g dedicated to each wheel.

As late as the 1990s some German passenger railcars used a generator driven by one wheel to charge batteries. The rest of the world uses head-end power (HEP), but the advantage of the old German system was that no electrical connection was required between cars.

[biggoofball]

Originally Posted by snake

It's not the brakes that do the regeneration, it's the drive train and electric motor, which also acts as a generator.

Of course the vehicle needs to have conventional brakes too, since more braking can be needed then the regenerative process will produce.

exactly! Then the issue becomes:

How does one connect all 4 wheels to some sort of generator. I'm not saying it's impossible, just an issue.

[JFerguson]

Originally Posted by snake

It's not the brakes that do the regeneration, it's the drive train and electric motor, which also acts as a generator.

Of course the vehicle needs to have conventional brakes too, since more braking can be needed then the regenerative process will produce.

A good friend pointed that same point out to me. Ah well, at least I got folks thinking.

[Aviator]

I don't even want to think about trying this with 3 axles. That would be three wrecks, three sets of axles, a new suspension system since the torsion type from the factory wont work with a split axle......., but it is a great idea. I am glad you got me thinking.

[JFerguson]

Originally Posted by Jammer

The Sierra regenerative braking works using a motor-generator between the engine and the transmission.

It would work fine on an Airstream if you're willing to retrofit a suitable drive train less engine. For braking on both axles you'd want a twin screw setup, and a 4L60e transmission out of the Sierra, and the motor-generator. Then it's simply a matter of some controls and programming.

In general, traction motors are too heavy to be placed on the axle except for rail applications because the unsprung weight goes way too high, so the obvious solution of a planetary gear unit and a motor/generator on the axle won't work. That leaves the standard possibilities of either a solid axle (cheap but heavy) or a full-floating setup with independent shafts to a center diff or maybe to a planetary and m-g dedicated to each wheel.

As late as the 1990s some German passenger railcars used a generator driven by one wheel to charge batteries. The rest of the world uses head-end power (HEP), but the advantage of the old German system was that no electrical connection was required between cars.

You can actually take this concept one step further and have a trailer that could actually propel itself, like supplemental power on a hill or getting unstuck out in the boondocks. I was kind of inspired by what this guy did:

Electric Porsche 944

[JFerguson]

Originally Posted by Aviator

I don't even want to think about trying this with 3 axles. That would be three wrecks, three sets of axles, a new suspension system since the torsion type from the factory wont work with a split axle......., but it is a great idea. I am glad you got me thinking.

Oh I agree this is pandora's box! I dont' even want to think about what a modification like this would do to resale value.

[barts]

Interesting idea, but this is really better implemented on the tow vehicle. That way, one can descend hills using regenerative braking much as one uses compression brakes, and the trailer service brakes are left unmodified to deal with more emergency stopping conditions. Keep in mind that whatever energy storage mechanism is employed, it needs to deal with storing the power generated by retarding speed on long downgrades; for 14k lbs or more for trailer + TV this can easily be 100 to 200 KW - not something you're going to easily store quickly - that's 300 to 600 amps at 330 volts - an impressive battery charger indeed.

I built a hydraulic hybrid car as part of a master's thesis in mechanical engineering in the early 80s; I ended up using a hydraulic accumulator & pump/motor as it would store & discharge power at a much higher rate than an equivalent weight of lead acid batteries.

Storing all the available energy on a long descent is hard.

- Bart

[JFerguson]

Originally Posted by barts

I built a hydraulic hybrid car as part of a master's thesis in mechanical engineering in the early 80s; I ended up using a hydraulic accumulator & pump/motor as it would store & discharge power at a much higher rate than an equivalent weight of lead acid batteries.

Storing all the available energy on a long descent is hard.

- Bart

Wow!!! That is so cool. Do you have any pictures?

[JFScheck]

Originally Posted by barts

I built a hydraulic hybrid car as part of a master's thesis in mechanical engineering in the early 80s; I ended up using a hydraulic accumulator & pump/motor as it would store & discharge power at a much higher rate than an equivalent weight of lead acid batteries. - Bart

Kinda like the "air-accumulator" used by the Indians in Asia...