[brian_]

I would love to convert a school bus RV to electric especially if I could make it a kind of 4x4/AWD hybrid

If you are starting with a typical school bus you will need to entirely replace the front axle to drive the front wheels. For the rear, you replacing the rear axle and suspension, or mounting a motor somewhere near the middle of the bus to drive the shaft to the rear axle.

What do you mean by "4x4/AWD hybrid"? For a two-axle vehicle, AWD is four wheel drive and 4X4.

And why a school bus? If you convert to an EV, you are using little of the chassis. If you are mostly using the body, a school bus isn't a great starting point for an RV; the only good feature is metal construction (rather than sticks and plywood covered by fiberglass or aluminum, like a typical RV). It would be a lot easier to start with a motorhome which is cheap because it has an old or broken-down engine and transmission, since those are the parts you don't need.

Shouldn’t this be quite doable with in wheel motors and a controller of some kind?

Wheel motors sound cool, but are undesirable in almost every way.

And in practical terms, each motor needs a controller... not just one for the vehicle.

How would this be doable?

You can

• drive all wheels with one motor, using conventional 4WD components, or
• drive each axle with a motor, or
• drive each wheel (which means either independent suspension, or mounting a pair of motors on an axle)

There are many goals to set and decisions to make, aside from this choice.

 

[TheHex]

I would love to convert a school bus RV to electric especially if I could make it a kind of 4x4/AWD hybrid

If you are starting with a typical school bus you will need to entirely replace the front axle to drive the front wheels. For the rear, you replacing the rear axle and suspension, or mounting a motor somewhere near the middle of the bus to drive the shaft to the rear axle.



What do you mean by "4x4/AWD hybrid"? For a two-axle vehicle, AWD is four wheel drive and 4X4.



And why a school bus? If you convert to an EV, you are using little of the chassis. If you are mostly using the body, a school bus isn't a great starting point for an RV; the only good feature is metal construction (rather than sticks and plywood covered by fiberglass or aluminum, like a typical RV). It would be a lot easier to start with a motorhome which is cheap because it has an old or broken-down engine and transmission, since those are the parts you don't need.

Shouldn’t this be quite doable with in wheel motors and a controller of some kind?

Wheel motors sound cool, but are undesirable in almost every way.

And in practical terms, each motor needs a controller... not just one for the vehicle.

How would this be doable?

You can

• drive all wheels with one motor, using conventional 4WD components, or
• drive each axle with a motor, or
• drive each wheel (which means either independent suspension, or mounting a pair of motors on an axle)

There are many goals to set and decisions to make, aside from this choice.

I was hoping to avoid having axels all together with in wheel motors why are these undesirable?

4x4 is not the same as AWD all wheel drive allows some slippage to allow for the difference in turning radius between the inside and outside wheels also between front and back whereas pure 4wd does not which is why you should never drive in 4x4 on dry pavement people end up snapping axels that way.

A school bus because their tough as frig and they have some decent ground clearance RVs are like 6” off the pavement no bueno for off road ( not even a little) so not very parkable unless you happen to own a parkin lot

Also they’s cheap cheap cheap

 

[brian_]

Wheel motors

I was hoping to avoid having axels all together with in wheel motors why are these undesirable?

You still have axles with wheel motors. It sounds like you're trying to avoid jointed axle shafts (or "halfshafts"); many people seem to think that this is valuable, for some reason.

There are many extended discussions of everything that is wrong with wheel or hub motors; I don't think it's worth re-hashing in detail here, but just try to find a suitable unit in a production vehicle and you'll realize that it sounds better in fantasy than it works in reality.

 

[brian_]

"4X4" versus "AWD"

4x4 is not the same as AWD all wheel drive allows some slippage to allow for the difference in turning radius between the inside and outside wheels also between front and back whereas pure 4wd does not which is why you should never drive in 4x4 on dry pavement people end up snapping axels that way.

The reasoning is sound, but the definition that you give for AWD applies to any "full-time" or "permanent" four-wheel-drive system. Terminology varies by manufacturer, and even by model within a manufacturer, so don't make too many assumptions about what a term might imply.

 

[brian_]

School bus considerations

A school bus because their tough as frig and they have some decent ground clearance RVs are like 6” off the pavement no bueno for off road ( not even a little) so not very parkable unless you happen to own a parkin lot

Also they’s cheap cheap cheap

There is a huge variety in RVs. My Class A motorhome is built on the Ford F53 chassis (the only gasoline Class A chassis currently available in North America), and is very much like a school bus in components. I have never jacked it up (I don't have a strong enough jack even if I wanted to), but I have crawled around under it to change the oil and similar tasks. Almost every conventional Class A you'll find in North America from the last couple of decades is built on either the F53 or the equivalent Workhorse chassis (which is now out of production).

Common Class C motorhomes (built on a truck/van cab and chassis) are typically on smaller truck chassis, and do tend to be lower.

I rode school buses for years, and I can believe that used ones cheap (and very worn out)... but there's not much to them that's desirable... except I suppose that metal body. As I have suggested in previous discussions, at least consider getting a forward-control/flat-front model (sometimes called "Type D"), for more usable interior space in the same overall length, compared to the classic conventional-nose type. My guess is that the rear-engine flat-front buses are more expensive than the front-engine; you're tossing the engine anyway so either could work, but the proportions may be different (at least at Blue Bird, rear engine have the same overhang in all sizes to suit the powertrain, while longer front engine buses have more rear overhang to keep the rear axle load suitable).

I think the ideal school bus to convert would be Blue Bird's All American RE Electric. It is the flat-front design, and yes... it is already electric! I'm sure it wouldn't be cheap, but all there would be to do would be the RV conversion and any updates/upgrades you want to do to the electric powertrain... perhaps including adding drive to the front. Blue Bird says they've been selling electric school buses since 1994, so maybe there's something used out there, even if it isn't the current model.

Although the conventional-nose design makes no sense to me, the Lion electric school bus is interesting because their website gives a little bit of technical information. They are using a motor (and probably lots of other components) from TM4. The LionA and LionM look very good, but won't be available as used units for many years... they're not even in production yet.

Any school bus has a main door which is barely adequate for weather protection, and placed just where most people would want a passenger seat. I would consider eliminating this door entirely, filling in the stairwell to put comfortable seating there, and putting a proper door further back (like any front-engine motorhome). These are body-on-frame vehicles, so you can cut in a door without collapsing the structure.

 

[TheHex]

4x4 is not the same as AWD all wheel drive allows some slippage to allow for the difference in turning radius between the inside and outside wheels also between front and back whereas pure 4wd does not which is why you should never drive in 4x4 on dry pavement people end up snapping axels that way.

The reasoning is sound, but the definition that you give for AWD applies to any "full-time" or "permanent" four-wheel-drive system. Terminology varies by manufacturer, and even by model within a manufacturer, so don't make too many assumptions about what a term might imply.[/QUOTE
Well according to the textbooks that’s what the difference is between AWD and 4X4

 

[brian_]

Well according to the textbooks that’s what the difference is between AWD and 4X4

"4X4" is part of a long-established terminology which indicates the number of wheels and the number of driven wheels. In that system, there is no distinction between part-time and full-time.

Naming of the operating modes of a 4WD system isn't an area defined by textbooks... it's a matter of common practice.

If you go through the online build and price system (configurator) for a Ford F-150 you choose between "4X2" and "4X4", but the higher trim levels of the F-150 have a full-time system. So much for reading too much into "4X4"...

 

[TheHex]

Well according to the textbooks that’s what the difference is between AWD and 4X4

"4X4" is part of a long-established terminology which indicates the number of wheels and the number of driven wheels. In that system, there is no distinction between part-time and full-time.

Naming of the operating modes of a 4WD system isn't an area defined by textbooks... it's a matter of common practice.

If you go through the online build and price system (configurator) for a Ford F-150 you choose between "4X2" and "4X4", but the higher trim levels of the F-150 have a full-time system. So much for reading too much into "4X4"...

It’s a matter of common practice because it had to be defined at some point like everything else.

I can say it’s true name is super drive and start selling under that name but that doesn’t change the fact that it’s truly all wheel drive.

This is like saying a tomato is only called a tomato because everyone agreed to it it’s a ridiculous argument.

Common terminology is full time systems are AWD and if they can also lock up they are a combination of AWD and 4X4

 

[brian_]

I guess you should explain to Ford how they are wrong about their F-150 system. While you wait for their laughter...

All I can suggest is being clear about your actual system requirements and design intent. For instance, do you want drive to both axles all of the time, or only when required, or only when selected by the driver? If only one axle is normally driven (in a system which automatically or manually adds the other axle), which one will it be? If driver-selected, do you need to allow for an inter-axle speed differential, or is locked together acceptable? When different axle speeds are required, what control features are needed: equal torque distribution? torque controlled to match speed difference to turn radius?

It's not at all clear to me which of these "a kind of 4x4/AWD hybrid" would be.

 

[TheHex]

I guess you should explain to Ford how they are wrong about their F-150 system. While you wait for their laughter...



All I can suggest is being clear about your actual system requirements and design intent. For instance, do you want drive to both axles all of the time, or only when required, or only when selected by the driver? If only one axle is normally driven (in a system which automatically or manually adds the other axle), which one will it be? If driver-selected, do you need to allow for an inter-axle speed differential, or is locked together acceptable? When different axle speeds are required, what control features are needed: equal torque distribution? torque controlled to match speed difference to turn radius?



It's not at all clear to me which of these "a kind of 4x4/AWD hybrid" would be.

Not trying to explain to ford how they’re wrong trying to explain to you how you are.
A full time capable 4WD system is AWD they’re the same thing but a 4x4 system that can stop slippage is a 4x4 system some can do both most cannot they’re simply saying theirs can do both ask any mechanic


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[brian_]

NA full time capable 4WD system is AWD they’re the same thing but a 4x4 system that can stop slippage is a 4x4 system some can do both most cannot...

Okay... so what do you want your system to do?