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Old 09-15-2015, 04:00 PM   #1 (permalink)
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Help me Daydream, Offroad Hybrid

Let me start by making this disclaimer: I will probably never be able to build this, and even if I could, its at least 10+ years off. I just want to enrich my mind and imagination by figuring out how it could be done. This would never be the cheapest or easiest, that's not the point. I enjoy the design and problem solving aspects of the build, driving it afterwards is just a bonus.

That being said, I want to figure out how to build a small rock buggy. I think I would want to use a hybrid ICE/electric/hydraulic powertrain. It would need to have enough low speed torque, and maybe have a top speed of say 30 mph. Fuel efficiency is not a primary concern, no matter what, 4x4's are always expensive to play with. I think with as little as I know about the specifics of regular hybrid technology, that I would like to run the ICE in series with the electric motor, primarily as a range extender. The electric motor would in turn power a hydraulic pump that would spin hydraulic wheel motors (mounted at the center of the axles). The two primary reasons to add hydraulics is because I feel these can be made survive harsher environments for cheaper than electric wheel motors. I also think that some clever valving could gain several features that might be nice to have in an offroad vehicle.

Perhaps I could try and complicate things by being able to bypass the electrics and run a hydraulic pump directly from the ICE as a sort of "limp mode", but I dont know how necessary that would be, nor how much more complicated it would be (or expensive).

Most of the questions I have pertain to electronics, but include a few other topics:
  • Is regenerative braking something I should try and include?
  • Aside from trying to recapture energy, can the electric motor be braked electronically?
  • Are there motors available with that would allow me the low end torque and high speed without the use of a gearbox/transmission?
  • Aside from weight, what are the primary benefits of using more advanced batteries than say AGM lead acid?
  • If sticking with a series hybrid, what is the most efficient type of ICE, and what kind of power cycles should it see if all it is doing is basically running a generator?
  • Anyway or reason to make the hydraulics do more than simply transmit the energy coming from the electric motor?

Some of the other details about this daydream:
  • Smaller than a samurai, larger than a side by side
  • two seater with tube chassis
  • 33"-35" tires
  • hydraulic valving to get park/reverse/neutral/forward
  • homemade solid axles
  • as quiet as possible

I am very open to different ways to build something like this, what might you do differently?

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Old 09-16-2015, 11:55 AM   #2 (permalink)
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Old 09-16-2015, 03:31 PM   #3 (permalink)
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Old 09-17-2015, 09:53 AM   #4 (permalink)
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come on hybrid guys, tell me what i am missing. ive read up on some of the forkenswift data, and maybe something like that is a starting point, especially since I dont think regenerative braking would be effective at such slow speeds.

also, Im starting to read about The DIY motor controller
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Old 09-17-2015, 10:12 AM   #5 (permalink)
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Im reading about that controller and i noticed something. The wiki says "Regen can be set anywhere from 0 to 300 amps per phase." This is under the "AC Motor Controller Features" found here. Is regen something that can be ramped up, like with a pot? Could this be used as a sort of brake?
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Old 09-17-2015, 11:28 AM   #6 (permalink)
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Quote:
Originally Posted by Donahue View Post
Im reading about that controller and i noticed something. The wiki says "Regen can be set anywhere from 0 to 300 amps per phase." This is under the "AC Motor Controller Features" found here. Is regen something that can be ramped up, like with a pot? Could this be used as a sort of brake?
Yes, but there's a HUGE gulf between automatic- and manual-control of that regeneration...ie: computer involvement!
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Old 09-17-2015, 07:50 PM   #7 (permalink)
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Originally Posted by Old Tele man View Post
Yes, but there's a HUGE gulf between automatic- and manual-control of that regeneration...ie: computer involvement!
i didnt know if it could be rigged up to a pot to act like a brake pedal. manual hydraulic brakes would probably be sufficient though.
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Old 09-18-2015, 11:02 PM   #8 (permalink)
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I don't know any reason for the electric part, except for Regen, but if your going slow there will not be much of that I'd think. Here is a thought for drive layout if going Hydraulic, it's a Concrete Extruded curb machine. Each of the three legs steer independently and move up and down independently, for rock crawling you'd probably want four, and have wheels at the bottom instead of steel tracks. You would be able to move each wheel up or down to maintain the vehicle attitude, and each wheel would be steerable...it could turn all the way around in it's own length. I am working on a "Light weight" Electric two seat UTV type of machine, which I'd like to add a generator to for onboard charging...a Hybrid. It's story is under the Hybrid section. Good Luck!
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Old 09-19-2015, 05:24 AM   #9 (permalink)
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I'm not an expert but I think I can help steer you in the right direction. I'll attempt to answer each of your points.
Quote:
Most of the questions I have pertain to electronics, but include a few other topics:
Is regenerative braking something I should try and include? Your hydraulic drive would have accumulators that help control speed both forward and reverse as well as brakeing, much like electric regen.

Aside from trying to recapture energy, can the electric motor be braked electronically? Yes with full control either way. but see above.

Are there motors available with that would allow me the low end torque and high speed without the use of a gearbox/transmission? Absolutely. Electric motors are ideal for huge low speed torque but some also can attain very high speed with enough voltage.

Aside from weight, what are the primary benefits of using more advanced batteries than say AGM lead acid? Yes, sag, lead acid suffers from voltage sag under heavy load lithium based batteries much less so.

If sticking with a series hybrid, what is the most efficient type of ICE, and what kind of power cycles should it see if all it is doing is basically running a generator? With hydraulic drive a small diesel may be used to pressurize the system or recharge the battery.

Anyway or reason to make the hydraulics do more than simply transmit the energy coming from the electric motor? Hydraulics are very flexible systems. you could do almost any thing you imagination dreams up.
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Old 09-19-2015, 06:51 AM   #10 (permalink)
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Originally Posted by hamsterpower View Post
Are there motors available with that would allow me the low end torque and high speed without the use of a gearbox/transmission? Absolutely. Electric motors are ideal for huge low speed torque but some also can attain very high speed with enough voltage.
It is a function of the size of the motor, so yes, but it is gonna be heavy IF YOU HAVE NO GEARS!!!

The tesla roadster has about 8.25:1 gear ratio IIRC. But you are not going to find a motor that can drive a single speed gearbox AND lift a heavy homebuilt thingamabob offroad rock climbing AND push it down the hiway. Multiple gear ratio choices certainly would be a good call there.

electric motors arent magical. And adding volts adds weight for a given torque, so less climbing.


Last edited by P-hack; 09-19-2015 at 06:59 AM..
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