Help with electric drive train for vehicle

[Super7800]

This might be the wrong place to ask a technical question like this, but imma ask anyway (lol).

First, let me describe the very basic plan. I plan on bringing a mutant vehicle to bm 2023 (or 2024 if I run out of time, or it gets rejected). It will have a 60-75 kw diesel generator at its core (the design permits 5+ inches of spray foam around the engine, and will have an extreme muffler, and as it's a sound car, this should suffice I think for noise). The frame will be built 100% from scratch. It will use a dual trailer axle setup for the rear, and for the front a truck axle with drive (probably from 3/4 or 1 ton pickup). It will be a front wheel drive vehicle. I'm planning on designing it for a maximum achievable speed of 10mph (I'll settle for 5 though, as it won't go faster or near 5 at bm anyways). It will be 25 to 30ft in length (excluding "art" features), and I estimate it to weigh 8000 to 14000+ pounds without people (in truth I have no idea what the final weight will be). It will be a fairly potent sound car, with room for quite a few passengers.

I believe that is all the needed background for my question which I request guidance on, which is how to setup drive train. I will have 220 three phase power from the gen. I would like to do electric drive from a vfd. Would a 10hp 7.5kw motor be sufficient? I figure that I should use electric as one diesel engine seems more reliable and fuel efficient than two. What gearing should I use if any, to achieve a maximum of 10mph (5mph maximum on playa)? Do I need a transmission, or would one set of gearing suffice? Would direct drive to front axle drive work?

I am an electrical engineer, so I have a basic understanding of mechanical, however as I've never done this before I'm abit stumped as to how best to implement front drive train. If my question is not clear, please ask for any clarification. Thanks.

[motskyroonmatick]

You need brakes and a parking brake. Custom from the ground up is fun to think about but trust me on this... Starting with as much stock drive train as possible is much easier. If you insist on it being electric power then consider using a long chassis flat bed truck with a manual transmission and attach the motor to the input shaft of the transmission so you can select from the speeds and direction of travel with the gearbox. Having steering and brake assemblies already present will really help. A cabover design original base vehicle may help with overall flexibility of design. Gross weight capacity really matters so add up the weights and see where that gets you with a chassis gross weight spec you will need.

[Super7800]

Yeah brakes are important. The tandem trailer axle I plan to use has them, and I will likely install the same style of brake on the front. (Electric trailer brakes)

I plan (and am very open to changing this plan) to make the frame from scratch, as it won't be trailered up there, it will be the trailer, i.e. remove front wheels, hook it up to a hitch. At bm the front "art" will hide the tongue. I have over 4000 mile round trip (from mn) with this thing, so I figured that'd be my best bet. Will electric trailer brakes not be good enoughph, or will I need to use hydraulic like cars do?

I'm 100% open to suggestions on electric vs diesel. I have a few extra kw on the generator to spare, so I figured a electric ac motor would be more efficient, less noise, and more reliable, but again if I'm wrong on that assumption I am open to recommendations.

I almost bought what you where suggesting (went as far as getting a trailer ready and driving halfway there), but my buddy who has done this stuff before talked me out of it, as their argument was that due to my custom needs it'd be better to start from scratch. As I haven't purchased the steel yet I am yet again open to suggestions.

Yeah weight is going to be an issue, especially with people I think. The plan was a tandem axle 6,000 pound each. With the slow speed and how forgiving leef springs are I wasn't terribly concerned, but if it comes to It I could do triple axle, but those eat tires for breakfast lol. I will have to weigh the generator and sound equipment before I get a good estimate.

How difficult do you think it would be to rig up a manual transmission to a front wheel axle and electric motor? I'm not concerned with steering as any front axle I get will come with the full original steering setup. When I get the front axle I should also try to get the matching transmission with it I suppose.

[some seeing eye]

Welcome to ePlaya. I bet someone could list the active BM MV forums.

I would start your research with commercial EV trucks in research and development. Trucks come in classes based on weight. You need enough torque to get them moving from a stop.

Generators on the playa are load following. They adjust the Amps out based on load by controlling the fuel and the excitation power. So you want your total system to be in the range of your generator capability.

The sound systems have their own engineering and essentially unlimited budgets. Because you are not running the sound system from the infinite grid, people do exotic things like supercapacitors. I'm in the camp that louder is not better, so I would suggest downloading https://www.cdc.gov/niosh/topics/noise/app.html. It is accurate for the price, and worth running on an old iPhone if your main mobile platform is Android.

It sounds like a fun project.

[Super7800]

I believe I have more than enoughph juice. The generator outputs more current than most residential homes get from the grid, so powering the sound system is a non-issue, atlest for my planned scale. It runs off of mains ac 110v and 220v, so super capacitors and batterys are fairly useless. I'm a lover of loud music. The goal is around 30kw rms sound system. Will that be achieved in the next year or two? Probably not, but I want to lay a good foundation to work on. I have a 12kw rms sound system already prepared and set aside for this project. (And yes I know the noise rules). But right now I'm focusing only on making it drive. That's the only unknown I have.

Good point on starting torque. Starting torque is where motors like these excell at. The question becomes sizing. Is 10hp enoughph (roughphly equivalent to 35hp combustion). Evs all use motors with very different goals than me. If this thing ever goes faster than 10mph than something catastrophic has happened, and if it can get from 0 to 5mph in under 3 minutes I'd be very happy.

Yeah I hope it'll be fun, and that I'll be able to get it done in time. If not there is always 2024 and beyond.

[Token]

Before you go down the path of “I have plenty of juice”, please allow me to present some data from a real vehicle I own.

The Chevy Volt.

Like your design, it has an ICE engine running a generator, which in turn spins electric motors for propulsion.

The 1.4L gasoline engine is rated ~ 63KW mechanical output and drives a 53KW electrical output generator. 10KW is lost to thermal inefficiency.

The drive motors to the wheels are 111KW, but they are battery buffered (18KWh battery but ~ 4.4KWh used for said buffering).

Now, this is a vehicle designed for regular driving, acceleration and high speeds 70mph and higher, but it is a good baseline to illustrate some points;

Power vs Energy - don’t lose sight of this key difference - this will influence your budget coming off the big diesel generator. My passenger sedan, that for simplicity we say is 3000#, has power needs higher than your application at 10mph, BUT it will have lower energy requirements - because of the weight difference.

F=ma=mv^2

Then you go angular momentum on it, do torque conversion, which gets you to the motor capability - get that Nm range to move the mass you expect to accelerate from Locked Rotor to max efficiency.

Once you have that number, you go play with gear ratios to match max efficiency at full KV speed vs max current and power needed.

Notice the term “Locked Rotor” - this will be the most important spec on the motor. It will tell you how many Amps that motor will chug at max-current-draw.

You have to ensure that the Locked Rotor doesn’t spike the amps draw and clip your sound system.

Moral of this long ass post: spend some time doing math up-front for the worst-case weight and load situations. Do it for both Power and Energy. Doing Work calculations doesn’t hurt either.

Dust off the old Physics books!

You are in the right place. Bring the details and we will chip in some figuring.

Disclosure: I design vehicle powertrains and Li batteries to pay the mortgage, and am terribly opinionated on that subject.

[Super7800]

Screenshot_20221008-140643_eBay.jpg

Screenshot_20221008-141743_eBay.jpg

Here is what I have for a 10hp motor. I can go out and purchase another, but as I already have this one, if it could work that might be nice. It is off of an old Mitsubishi cnc mill.

I don't see a locked rotor spec on the nameplate, only an amp rating of 31A. I must admit I always sucked at physics but yeah calculating it out would be my best bet.

Acceleration from 0 to 5mph in 3 minutes is 0.012418 m/s2

For mass let's say worst case with lots of people 14000 pounds (will it weight this much I don't know).

F = ma = 14000lb x 0.012418 m/s2 = 78.86N

Now after getting that, it would seem that I do indeed need to relearn a thing or too, as I dont seem to recall how to calculate out the rest.

[Token]

For mass let's say worst case with lots of people 14000 pounds (will it weight this much I don't know).

F = ma = 14000lb x 0.012418 m/s2 = 78.86N

Now after getting that, it would seem that I do indeed need to relearn a thing or too, as I dont seem to recall how to calculate out the rest.

Let’s say 14000# is ~ 6500Kg.
10mph is ~ 16Km/h
16Kmh is ~ 4.444 m/s

Let’s also say you use a regular pickup truck tire; something like a 265/75/16 LT to carry all that load.

Tire circumference ~ 2.5 meters.
Tire radius ~ 0.4 meters.

Now, let’s say a reasonable acceleration from standing still to 16kmh is 8.8s - this would be really slow in the real world. We can make it slower later …

So…

Acceleration is 4.444mps / 8.888s = 0.5mps^2

The rig is 6500Kg —> F=ma

6500 x 0.5 = 3250N of force.

So if you strap a jet engine with 3250N of thrust - you get to 16kmh in 8.888 seconds.

Good number that force.

Let’s turn that with a direct drive motor and see what torque we need.

The radius of the wheel is the lever that will convert the linear force into the rotational force. Since the angle is always 90 degrees Sin(90) = 1 …

Torque = F x L = 3250 * 0.4 = 1300Nm

That is the magic number at your wheel to ground interface to get this thing moving.

In SEA that is just shy of 1000ftlb - just about what my big diesel truck puts out when I gun it.

I’ll stop right there to let the numbers sink in a bit. Also gives you time to plug in variations like making 0 to 16kmh 13 second, 18 seconds etc.

Next step is calculating the gear ratios needed to get the 3600 rpm motor down to what matches the wheel diameter and circumference to fit those acceleration requirements. That is where we will determine the size and power of motor needed.

[M F Bonz]

Honestly …I think you are a little light in horse power for this Application.
Getting 10 hp down to the ground can be a problem.

If you get into some soft dust…
You don’t want to tell people… “Get out and push everyone!!!”

Don’t over think it too much.
Most the stuff you need for the build already exists.
Forklift/trencher/equipment salvaged drives work very well. Adapt the Motor with some old junkyard equipment already meant to go slow.
Electric forklifts comes to mind for an idea of horsepower and power consumption needed.
Just go look at all the equipment and how they solved the drive problems…. This also gives you an idea on how it might work for you in the desert.

Just a thought.

I’m working on something that could easily be adapted to Electric.
But… I’m looking to use bio diesel so it smells like French fry’s as I drive by. And…. Some other FX things on it needs the bio diesel.

So..
I’m really enjoying this thread so Don’t mind me …just thinking out loud… that’s the squeaky clicking sound you hear.
please continue.
Thanks.

[M F Bonz]

I liked the drive used on the Despicable Me rocket car built for the burn.
I don’t remember the Horsepower. And I can’t find the build link…but it was a very simple gasoline motor drive. Just a chain drive motor mounted on top of a narrowed car rear end as I remember. Great build.
Wish I could find the link. I think it could be easily converted to an electric drive. I don’t know how well it worked in the Desert. But I still liked it. I suspect they needed more horsepower to get across some tall playa snakes.

But don’t we all.

Your VFD controller should allow you to fine-tune the speed.
Do I understand correctly… that the controller is going to be your Throttle? If it is…How will you incorporate the dead man switch?

Driver safety controls are going to be Important for DMV registration.
I Believe they even require some proper lighting with working tail lights and Brake lights now.

Captain G. can ring in on the Drive unit he used for his boat. Also a brilliant choice in my opinion.

[HarryN]

The VFD approach is a good one, but usually the motor torque is decreased when run at lower rpm vs higher rpm IIRC.

There is also the cooling aspect to consider. When a motor is run at low rpm, the fan on the drive shaft is also running at a lower rpm - so less cooling.

The EV designer in the thread can help you with the detailed calculations but my quick math indicated that you will need 4 of those motors to be viable and at least a 3:1 belt drive.

If you go on line, it might be possible to find a similar motor sold (new) with more detailed specs and torque curves for the calcs.

[M F Bonz]

I agree.. when you start pushing an electric motor outside it’s designed parameters you are setting yourself up for other problems.

That’s why I suggested looking at what’s already out in the Industry.
And simply adapt it.
The more I think about it the more I like the Volt idea. Everything is there.

I know it’s a burner thing to reinvent.
I get that.

My own build has some stupid overkill complicated electrical, pneumatic and hydraulic systems… but that’s what’s fun for me. How to make it unique and bullet proof for the desert. I may steal the Volt idea.
Is a Volt a front wheel drive?
Mine is a six wheel steering design.
The drive axle needs to steer.
So I can crab crawl the car when I need.

I added one Odd parameter to this build.

It’s being mostly built with broken, free, donated, and almost free parts. I have some good resources to find what I need. That helps.

All Builds for the desert should be considered Harsh environment builds and design as such.

The motor, controller and controls should be sealed or a sealed type for the desert environment. And yes even for a wet environment. It does rain occasionally out there.

Playa dust loves to kill Electronics.
It’s quick and efficient at it.

Smiles ~

[Token]

I’ll post the second part of the deep dive this weekend.

It won’t actually be that bad in terms of electric motor size and capability.

Probably will need ~ 100 Nm or so of grunt via a 30:1 gear ratio. Not terrible.

Finding a motor that has that torque at low RPM but then spins up to 3600rpm - might be a pickle.

@Harry - electric motors have max torque at low RPM but max power near max RPM.

[HarryN]

30:1 gear ratio is not a big deal for a normal location, but on the playa I would suggest considering to do it with a belt drive (due to the dust). 3:1 ratios are more common in a belt drive system but you are the expert.

[Molotov]

You might just look for a wrecked Toyota Prius Hybrid that has a sound frame, battery and motor. Cut the body panels off and build from there.

[M F Bonz]

DAAC26DF-2872-464C-9EAC-8E45379F68BF.jpeg

rendering of a four wheel steering version.

[Super7800]

So what I'm hearing is that if I want electric drive, I probably can't get by with a 75kw gen. I'm going to look at and possibly purchase a 150kw unit this Tuesday powered by a 855 cummins. That should allow me to devote 50kw+ for three phase ac motor(s) to drive the thing. The goal is to simplify the drive, not complicate it. This rules out completely the use of a canabalized drive from an electric vehicle. I figure one big diesel is better than two small diesel. Only have to maintain and bring parts for one engine (as a sealed ac motor should survive very well on playa).

[M F Bonz]

Then just use a hydrostatic drive axle and use the three phase motor to drive the hydraulic pump.

One and done.

You can purchase just the axle, pump, and hydraulic lines so no need for a donor vehicle.

A hydrostatic steering drive is what drives and steers the back of the car rendering above. The drive can be new or used. Lots to pick from out there.

I saw one that was a 2 1/2 ton rated axle.
recently I saw one for about $500 for a complete axle with brakes.

C24976BE-A715-4A9F-9FBC-49278B823D87.jpeg

What ever you do… please share.

[Super7800]

Huh interesting idea with the hydrostatic axle, definitely something I'll look into. Idk about weight capacity though. The generator alone will likely weigh over 7000 pounds (and I'd mount directly above the rear axles). I was looking to possibly use the front axle off a semi, but before I decide a front axle Ill have to figure out worst case for weight resting on it.The current thought is to get a 40ft gooseneck trailer and convert that, but idk yet. I will definitely document the project, I considered perhaps doing a YouTube build log, but I hate editing video lol.

[M F Bonz]

Randomly pulled copy/paste from the Internet

“”””. Machine design:
Hydrostatic drives are widely recognized as an excellent means of power transmission when variable output speed is required. Typically outperforming mechanical and electrical variable-speed drives and gear-type transmissions, they offer fast response, maintain precise speed under varying loads, and allow infinitely variable speed control from zero to maximum.
Unlike gear transmissions, hydrostatics have a continuous power curve without peaks and valleys, and they can increase available torque without shifting gears. But despite the superior performance of hydrostatics, a major drawback has been higher cost compared to their mechanical counterparts.


OME off road:
Hydraulic drive systems make some of the off-highway equipment industry's most unique vehicles possible. Unencumbered by driveshafts and chains, hydraulic drives give engineers the ability to design a specialized machine around the job it is supposed to perform — whether that's loading luggage into the new Aerobus A380 in Frankfort or harvesting raisins in California's San Joaquin Valley. Engines can be placed where it is convenient and hydraulic hoses can be routed down to motors that propel the wheels.

For many of the firms that supply the hydraulic drive systems and their components, it's in the new and unusual applications that the fun resides.

”””””

I don’t think size is going to be a problem.


You’ve got the money honey they probably have the axle for you.

Find a local hydraulic shop that takes care of the big machinery around your county/state.

Good luck take pictures.
Smiles~

[Super7800]

So I am now the proud owner of a 150kw diesel generator, powered by a cummins 855 engine, and according to the crane operator weighs 7800 pounds. I will likely never drive it above close to maximum. It is an older unit but has less than 200 hours so it claims (I don't believe it, but the engine itself is in amazing condition). Before purchasing I have looked at and inspected manny 75 to 150kw generators, and this one was just about as loud as the others, but was in the best mechanical condition, and the price was right. Now comes the elephant in the room, noise. This thing is loud. If you've never heard one lucky you, it will rattle your windows and your soul. How might I go about quieting this thing? This will be stripped of its outer sheath and live in a "engine room" of the vehicle. My first roughph and ready idea would be to encase it in 1.5ft of spray foam insulation on all sides (1 ft under), obviously engineering in enoughph clearance for maintenance. And to both get bigger and to double or triple up the mufflers, and mount the whole thing on a bunch of rubber isolators for vibration. However there will still need to be two massive vents exiting this encasement for the radiator, which would lead to alot of escaped noise. Any suggestions? I really don't want to do a bunch of expensive "trial and error" type things, so the more overkill the better.

But now back to the topic at hand. I figure I can now budget a 30 to 50hp ac motor. I figure this should be more than enoughph, but I'll let the experts answer that (lol). I still don't know whether hydrostatic vs transmission, I figure hydrostatic runs the risk of hydraulic leaks (if it ain't leaking hydraulic fluid it ain't got any lol), and would cost significantly more, although it also would be simpler to implement, and might have less long term maintenance costs.

@m f bonz what driver safety would I need? I figure it would have the exact controlls as a regular car. Is that not sufficient? My first thought would be a Deadman seat like what's on riding lawnmowers, but what other safety regulations for controlls are there? When I looked at other vehicles they all seemed to just use the normal vehicle controlls. Yes the vfd will be the throttle, connected to a foot pedal like a car.

If anyone has experience with diesel gens, I am in need of advice for controlls and maintenance. I will be replacing pretty much everything but the core components, all new controlls, hoses/ lines, new electric governor, etc. I'm looking at the basler DGC-2020 controller, as that seems to be the easiest to configure.

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[M F Bonz]

9D57F9E5-5C27-47DE-9C32-55D40C56E7E1.jpeg

You would be surprised how many hydraulic systems are used at the burn.

It’s Just a guess… but probably Every scissor Lyft and high reach lift out there uses hydraulic systems including hydrostatic drives.

The burn could be considered light duty use for these types of hydraulic systems on a mutant vehicle.

Shovel and a bucket for easy clean up. Carry replacement hoses and fittings.

New Well designed system shouldn’t be a problem for leaks and failures.

As far as safety controls. I was interested in how you were going to integrate your controls.
Whatever you use when I say “dead man switch” all I mean is when the driver releases the controls everything should be “all stop” You shouldn’t have a continuous movement of the vehicle after the driver releases control.

I’m using hydrostatic but that’s just my preference. I also have access to parts in the Industry. So that makes it cheaper for me.

I’m still interested in what ever you choose for what you’re building.

I’m also interested in how you solve design problems.

Don’t risk overheating for your sound proofing. It would be very quiet if it wasn’t running at all.

How you transport your vehicle also needs to be considered in your design. You need to get it there and back. Will it survive going down the I highway at 65 mph in hard crosswinds?

Thanks
looking forward to seeing more.

[Super7800]

Yeah soundproofing without overheating would be a challenge, which is why I very much would like to hear others solutions as it seems possible as I've definitely heard of it being done. My idea for a design would place people a few feet above the generator, so it is definitely something I'd need to engineer well. I'd think to suck air from the side and vent out the same side, whatever I do for the cooling, ductwork would connect it direct to the radiator (blowing over engine and gen). I might double or triple up the intake filter, to really help keep playa dust out.

The plan at this time is to convert a 40ft gooseneck trailer, and assemble all the "art" and speakers on playa (basically look like a crazy semi box when towed).

I won't be starting on the frame until this spring, so plenty of time to decide and collect parts for a drive system.

[M F Bonz]

89B7C9FF-3135-499F-BD85-2690EA5BC3F1.jpeg

Not many people on this board anymore.
Don’t get discouraged if people don’t respond. The few who are still here are pretty knowledgeable though.

Assembly on the Playa …. yeah …just make sure you keep that to a minimum.

Simplify and pre build everything and don’t make assembly too complicated. You really don’t want to be working your ass off on a mutant vehicle assembly in the desert.

Making it simple gives you more time for use. And less time for tear down at the end of the event.

Baffling is what I’ve always thought to use for generator sound reduction.
But that was for generators on the ground in a camp …not for a mutant vehicle. Not sure how that would work.


Cooling and noise reduction On that behemoth… I think it’s going to be your largest issues.

An old extra cooling trick. Would be using a windshield wiper pump and squirting small amounts of water on the front of the radiator.

The evaporation helps with cooling. It’s not for continuous use or to maintain cooling…. it’s only to help temporarily cool down the motor if it was under a hard load.

Sounds like you just need an electric trailer dolly. Then someway to steer it.
Laughs ~

[Token]

Stick tap to the Bonz for bringing up the hydrostatic drive …

… go find yourself a mid-sized tractor with a blown engine but good hydraulics …

Should be able to drop in a 3-phase motor to run the pump, with some metal fab of course.

RPM matches up well for replacing a diesel with electric that probably redlined at 4K RPM on the tractor. Plus, you don’t gotta worry about startup loads and such - all buffered and decoupled by the fluid drive.

Designed for max torque and low top speed.

Spit out the sound and cooling problem in its own thread. Totally different topic.

[Super7800]

Most if not all tractors that I've seen don't have axles that have both drive and steering on the same axle, but im sure if I started looking I'd find one. Might be more hassle than it's worth to get a whole tractor just to rip out the axle and pump, but it is definitely an option I will keep an eye out for.

Would mounting a suitable hydraulic pump to a 30-50hp motor, and connecting the other end to a hydraulic motor coupled directly to the front drive shaft of a truck axle work? Otherwise I'll just look for an axle like bonz showed a picture of. Does this kind of drive need a special type of hydraulic pump?

[M F Bonz]

Well a blind squirrel… Smiles

Super… I think You are thinking old school tractors.

Lots of newer hydrostatic drive tractors are four-wheel-drive now.
Even smaller ones.
Tractor shops would be a good resource to look for a hydrostatic drive.

What part of the country are you in?
Look for an equipment graveyard/Salvage.
Local hydraulic shop is your best resource to locate old equipment.

They may have something sitting in the back for cheep. That’s how I’ve been sourcing some of my parts.

Make friends with their hydraulic engineer/tech.
My son is a welder and works for Fluid Tech a major hydraulic shop here in Sacramento county.
Bonus!!!

For me I try not to reinvent stuff.
If something’s already engineered that fits my parameters… why not adapt it for my uses. Cuts engineering time and failures way down. And you can buy replacement parts… bonus!

Captain G’s solution for the Playa Cruser was brilliant as far as I’m concerned. That’s a perfect example of not reinventing but adapting existing technology.

Like you said …you have time. Do the local resource research.
Make some friends!