4WD Electric Off-Road Recumbent Pedal Assist "E-Bike" Build

[benthomsen]

Hi all,

I have been searching and browsing these forms for all sorts of info over the last 6 months or so gathering info for a design/build I am currently working on. Some awesome info and tips on here as well as some sweet builds.

As for my project the title basically sums it up. I'm pretty sure it still counts as a bike, hopefully ive come to the right place. I'm just looking for a bit of input really, general comments and ideas if anyone's interested. The design is well underway and almost complete, I have a full 3D CAD model and have built and tested a range of the components. Main construction is Carbon Fibre Tube and Aluminium.

I just need to nail down the electric side of things really and make sure the motors can push this thing along. Needs to be a bit of a torque beast, not looking for more than 50km/h on the flat. Just want to be able to handle grass, dirt, mud, sand, and snow with ease.

Total Weight - 90-100kg MAX (excl rider) includes chassis, swing arms, drive gear, suspension, wheels, motors, batteries, controllers etc (this has been calculated and will be close to final weight)

Rider weight ~80kg

4x 28' Custom Airless Tires/Wheels - Weighing 6.5kg each MAX, plus motor weight of 7-8kg each. Will probably require a bit of torque, looking to reduce weight as much as possible (mostly for torque and unsprung-weight reasons). Wheels are off-road with thin rubber tread at 500mm wide, plenty of grip and a decent footprint with low ground pressure.

Pedal Assist - "electric chain" type, reduces complex mechanical links in the 4 wheel system and still get "pedal-assist" bike, eventually also use as a throttle with various "assist" power levels, basically a range extender. Crank with Gates belt drive to a motor for regen (possible 3 speed hub to spin motor at ideal rpm). Generator motor undecided.

4x Crystalyte Motors - Single Side Axles. Running 48-60V, guessing 1000-2000W each. Currently deciding between HS4080, HS3540 or HT3525. All depending on weight, torque, power etc.

2x Roboteq HBL2360 Dual Channel Controllers - 60V, 2x 75A Max (50A cont), regen, reverse and also looking at programming/scripting a form of electronic diff-lock or traction control across each pair of motors.

Batteries - 48-60V Undecided, haven't really got that far.

Any ideas which Crystalyte motor to go for? am I going to have enough power for a decent launch to get out of holes, over bumps, up hills etc? battery size and power? or any experience with the controllers would be great. I have plenty of space on the chassis for batteries. Hope that's enough info for now, I've got a pretty clear picture in my head anyway. Happy to answer any questions!

Thanks! Ben

 

[shenzhen_ex]

...Wheels are off-road with thin rubber tread at 500mm wide....

I am not able to visualize your build concept especially because of the "tread" size. Are they ATV wheels?

...4x 28' Custom Airless Tires/Wheels...

Feet are express with a '. Inches are expressed with a ".

...I have a full 3D CAD model

Please post an image of your 3D concept...

 

[kudos]

I don't think there's many single sided hub motors available.

ebikes.ca do the M3540SS which is a crystalyte HS3540 single sided.......

Sounds like a cool project though.

Will be interesting to see how the motors affect one another when moving.

Kudos

 

[dogman dan]

28" wheels and hubmotors is a poor choice. I'd say 20" wheels would give you lots more grunt on hills.

But on the other hand, 4 hubmotors is potentially 12,000 watts. Would take a lot of battery though, to run them at more than 4000w total, 1kw each.

24" wheels might be a good compromise.

If at all possible, support the motors on both sides. Cylte axles are notoriously soft. Off road, I see them snapping off regularly.

 

[parajared]

Your lightest solution is going to be something along the lines of a drive shaft and one big motor. This is because four hubs plus thier enclosures, and four controllers and all their attachments will most definitely weigh more.

Your easiest solution will be four hub motors. On big hubbed wheels at 60 volts it will most definitely suck. This is because BLDC motors overheat like crazy when run below %50 their top speed so that would mean you would have to keep your ride cruising down the road something to the tune of 40 kph to keep stuff from overheating. This is ok for smooth hardpack roads, and unacceptable for say, crawling the thing up the side of a boulder, or gnarly trail rides or something.
Big wheels are kind of lame with hubs too, I'm not sure why, maybe it's a geometry thing or something, but small wheeled hub motors always run much more efficiently. I have observed this with my 20" hubs vs my 26" hubs.

You could undervolt to avoid the %50 problem and assuming you can run a max of about 50 amps down unmodified hub motors, you could make a rock-crawler style setup using crystalyte G series hubs and 24 volt controllers. This would keep the revolutions per volt down topping you out at around 10mph and since 24 volts x 50 amps = 1200 watts, you are looking at around 4800 watts of power for something like this.

Alternatively you could gear reduce 4 mid-drive motors to the wheels. This would allow you to run higher voltage and keep your stuff less melty because you wouldn't need to run as much amperage.

Personally I would say to hell with 4wd and run the motor to the rear shaft the way all the professional quad racers do it.

This sounds like a really awesome build. Can't wait to see this thing.

 

[benthomsen]

Sweet, thanks for the feedback so far!

As far as the wheel size goes (which is definitely not 28 foot, ill stick to my metrics), I was keeping the larger 710mm diameter and 500mm width to keep the volume up as they potentially will be able to keep the whole thing buoyant with no more than 200mm of each wheel below the surface. The tread is currently pretty low profile so buoyancy volume will be achieved by adding in some large foam plugs in each side of the wheel. Anyway this is something I was hoping to explore further down the line once I had my initial prototype built. If i keep the hub motors I may be able to compromise a little on diameter and bring them down if need be, at least to 26" or maybe 24" could be achievable without loosing to much of my required flotation volume.

I have been in touch with Kenny and have at least two options for single side motors (HS4080 and HT3525, plus the comment above mentioning the HS3540), with a ~17mm shaft. I would have thought this is enough to support the wheels, as I assume they are larger diameter than standard shafts? The design only allows for support on one side so this is my only option for hub motors really, so hopefully they aren't too soft!

I do have room for batteries so adding more juice would be easy design-wise. Interesting hearing about the 50% speed thing, as I definitely wont be cruising around looking for mileage and speed. Will be more stop start boulder crawling action (initial build name was the Crawler). Initial design was using an ASTRO with suitable reduction plus a gear hub, sliding driveshafts, SAMAGAGA differentials, with bearings and belts all over the place. It was complex and was going to require a bit more design time investment on my part before getting to something I could ride. 4 hub motors is quick and easy, get me on this thing sooner! But after hearing feedback actually doesn't sound too good performance wise! Possibly back to the drawing board, or just stick with the hub motors and try figure the most ideal setup. Lower volt higher amp option sounds interesting for sure. 4WD just makes this thing pretty appealing, its also 4WS all independent double wishbone suspension! Hopefully the 2 Roboteq controllers would also bring some interesting control options to the table.

Here's my one and only sketch to give a better picture of what I'm actually going on about, went from this straight into Solidworks (I'll post some CAD images once I get a little closer to build time).

View attachment 1

And here's my first full wheel mockup (without integrated hub motor). I have since refined design from to take it from 8kg down to 6kg.

 

[John in CR]

Looks like a great project. You want the slowest wind model of the 40mm motor. For the obscene price you're likely to be charged you should be able to get custom wound motors, but that's unlikely, since I believe those stators are purchased already wound. Have you checked into wheelchair hubmotors? I think they'd be a better match, because what you want is something that will turn only about 400rpm at the maximum voltage you're willing to run.

It's going to look slick for sure, and I hope you pull it off. My only question is about the one sided axles. The 50cm wide wheels will be able to put big off axis torque on the connection.

 

[shenzhen_ex]

WoW. Cool.

What about getting bolt on 4WD?
Front and rear go for $800 a set here in China.

Or use 2 of the front assemblies, 1 on the front and 1 on the rear of your set-up and and stay with your 4 wheel steering/independent suspension concept .

http://item.taobao.com/item.htm?spm=a230r.1.14.1.CcbifB&id=26783832932&initiative_new=1

http://item.taobao.com/item.htm?spm=a230r.1.14.158.I9Sxxr&id=27112116301

 

[benthomsen]

Sweet thanks again guys! I did briefly look at wheelchair motors, however I just saw they were all mostly low power and torque so didn't really give them the time of day. I guess everything can be pushed though. I could see what Kenny thinks about this "slow wind" business, could be willing to pay a bit more to get something more suitable. I'm almost leaning back towards the mid-drive now. I like the idea of playing with gears and having the ability to drop to a low gear, still run the motor/s at high rpm and get some serious crawling action. The axle size has crossed my mind, and mid-drive means I can crank them back up to 20mm OD.

Those bolt on parts are interesting, looks like a Chapman Strut type setup, not really suitable for my design though. This thing is pretty custom and all is looking pretty slick! Just need to nail down this drive system thing. As mentioned I did see this thing originally with an Astro mid-drive setup, so cranks and reduced Astro both drive a gear hub which then splits off and drives Samagaga diffs and down to the wheels. All this can fit pretty well, just a couple of issues with how to get reverse (will probably need it on this thing) maybe a separate gear mechanism that I engage and still pedal forward?! individual brakes also so I can lock a spinning wheel if it gets up in the air, and i'd run all this at lower gear ratios than your standard bike. Maybe this would be a good candidate for dual Astros? Giving me plenty of power to spin up the whole drive system. Whats the best source of info there? I guess I should check out all the Shumaker Tech stuff. Or any other motors I should look at for mid drive?

Also does anyone have any advice on internal gear hubs? Which ones will be able to handle the power etc. Or that Pinion P1.18 looks pretty cool!

 

[sigimem]

What is your total weight excluding controllers and motors so far?
In my opinion a astro drive is great for a a bike or something that must be lightweight. But for a project like yours you might also choose a tougher and cheaper motor with more torque and less need for reduction. Maybe a 5kw motor from http://www.goldenmotor.com/ or a mars etek motor. Maybe a brushed motor.
There are lot of options.
What is your budget?

 

[Drunkskunk]

Since you mentioned floatation, you plan to run this in water/deep mud, right?

If thats the case, forget hub motors, as they would end up submerged.

A single BLDC motor running two light weight (250cc or less?) 4x4 ATV Differentials and hubs might weight substantualy less. it would also give you the option of using a controller programmed with reverse, or even adapting the ATV transmission so you have a gear range that includes reverse.

 

[benthomsen]

Yeah I am still looking for lightweight, I want this thing to sit on the mud rather than sink in, same on the water (although movement wont be very efficient) I can see how hub motors could be an issue here, although the water floating thing wont be part of my initial testing. However an important thing is also a proof-of-concept type of approach. Get something rolling at this stage, have a bit of fun, maybe stick to racing along the grass, sand etc at a decent speed that i wont overheat the hub motors. If all goes well, my chassis is then fully adaptable to adding mid-drive at a later date, for the ultimate lightweight off-road performance. May possibly save me some headaches being my first electric build (first vehicle also), hub motors is definitely simpler, I am so back and forward on this its crazy. Ill get some CAD picks up soon showing the drive system concepts to give an idea of the challenges.

Total Weight is 50 - 60kg (excl rider, motors, controllers and batteries)

Build cost is $7000 - 8000 USD (excl electronics)

Electronics $3000 - 4000 USD

I kinda see three options.

4 Hub Motors - 24" 610mm wheels, possibly H4080 if I can get a slow wind or stick to the HT3525, play with voltages and amps. Maybe could go for a geared Hub Motor like a MAC 12T? Proof of concept, have some fun and tackle the next challenge from there. Still apply regen through pedal cranks if I get that far. Simple. Reverse is easy. May have heating issues running at low speeds for long periods. Stay away from water. May not have much launch torque, possibly could run a burst of power to help with launching? Just want some decent acceleration and to not be too disappointed with performance. But 4 hub motors, power to weight should be pretty good right? Its not weighing 4 times as much as a two wheel build. Or am I being a little naive.

Twin Astro Mid-Drive - Twin Astros reduced to the gear hub, pedal cranks to the gear hub to the drivetrain, possibly a Rohloff Speedhub for strength. Complicated first build, expensive too. Reverse is complex with all the freewheels.

Single Motor Mid-Drive - Use a large Goldenmotor HPM5000B or similar as suggested, reduce it straight to the drivetrain (single speed). Run pedal crank through a lightweight gear hub (maybe just a 3 speed or so) and freewheel it to the drivetrain. This could solve my reverse issue, as long as I can make it so it wont whip the pedals around in reverse, maybe the gear hub will prevent this. ATV or UTV drive components could also be worth looking into. I do like what Samagaga and Contes Engineering have on offer though, check out the Athos http://www.contesengineering.com/athos.html. As long as they can handle the torque.

 

[sigimem]

I must admit I have thought about a similiar vehicle. But I have never reached your planing status.
So I might be following my ideas instead of yours. Maybe its not what you want i will post it anyway
But in my opinion you should not consider your vehicle any form of bike anymore, because its not it is in fact to heavy.
Because of that I would look for more durable parts then bike parts for the drivetrain.
For what do you need a rear differential on a rock crawler anyhow?
You could also make something similiar to the edge buggies
with a disc brake and the drivetrain in the middle and these flexible shafts (what is the correct name?) attached to the wheels.
Of course it can be lighter than this concept example :wink:

 

[sigimem]

About the weight of the hub motors.
A Ht 5325 is 7,5kg without rim, a controller like a lyen 18 fet is 0,8kg. So you are at 33,2 kg with 4 motors and 4 controllers(maybe use single controller that would be larger does not make much difference in weight). Not including batteries and wires. A H4080 should weigh more than a Ht3525.

 

[benthomsen]

Thanks for the post, seems a cool space to be in. I kind of want to be sitting somewhere in between, the lightest crossover from a bike to a four wheel buggy I can get. In this case I do still want to consider it a bike. As I haven't seen any other vehicles doing this type of thing. Super lightweight with the advantages of large footprint and low ground pressure, meaning I can sit on top of sand and snow with ease and use less power to get around, and eventually find the drive system that will work best for it. Probably breaking some things along the way!

The setup there is pretty similar to what I am looking at though if I went mid-drive, just a lightweight version of it. I do see that the hubmotor setup would probably be heavier, also adding undesirable unsprung weight when compared to the sprung weight. But definitely the simpler option. Currently trying to compare this Crown motor from Crystalyte now too. More stator space for more windings. Maybe run it at a lower voltage and allow for plenty of current. See below some basic CAD visuals of the drive systems. Shown with 24" wheels.


View attachment 1

 

[SHARKBITEATTACK]

Looks like the lunar rover!

 

[shenzhen_ex]

...I have a full 3D CAD model

Thanks for the images. Are the images you posted of your "full 3D CAD model"?

I would really like to see the 3D model of the suspension area including the drive, steering, and brake components. If the model does not have those components yet, can you post a sketch?

 

[benthomsen]

Haha Ill see if NASA will give me some funding.

Nah these aren't the full CAD model, there is plenty more detail in the full one. Just wanted to show the drives this way as its much easier to see, they weave in and around the chassis/suspension/steering pretty tightly.

I will post images of the full CAD model once I get a little closer to finalising this thing, and if hub motors can satisfy the design then that wont be too far off!

 

[sigimem]

I see your point I tend to make things complicated, because of that my bike is far away from completed.
The Crown should have plenty of torque. I think you could use the ebikes.ca simulator and see if you can run the hub motors without getting hot. It will not be exact but a good guess.

I really like your idea of a large footprint on a offroad vehicle. You should try to make a scrub radius of zero with this wide tyres http://en.wikipedia.org/wiki/Scrub_radius (you might already did just wanted to mention it)

 

[izeman]

that's a cool looking project, but i don't think that you will be able to pedal it for more than some meters.
if you ride on sand your open wheel will fill with sand and it still will sink a bit. and it require loads of power to move a vehicle once the wheels are sunk into the ground.

 

[benthomsen]

Just waiting to hear back from Crystalyte regarding the Crown. I could possibly use the calculator on a single motor with 1/4 the weight, don't know how much its going to tell me though, but will play around with it. And yeah scrub radius is virtually nothing, could still be an issue with the wide tires though, my solution would be some steering assist. Electric or pneumatic actuators possibly, will cross that bridge when I come to it.

If I do go for the mechanical pedaling, this bike is geared lower than your standard bike. So its basically designed to go at lower speeds and travel less distance. The open wheel thing is an interesting point, I could always add a thin edge barrier or design an edge/angle to push the sand out when/if the wheel spins. Otherwise the flotation plugs will increase the side profile by a large amount.

 

[benthomsen]

Just thought I'd post a follow up, Crystalyte Motors and Roboteq Motor Controllers have arrived. I ended up going for the H4040s will run them at 48V with these dual channel controllers. May end up doing a phase wire upgrade also. Haven't had a decent inspection of the motors yet to check the wire bushing etc. Next step is to do some bench testing and see what these things can do.

 

[John in CR]

If you do upgrade the phase wires, install temp sensors while you are in there. With 4 motors they shouldn't be stressed unless you get in something like sand or steep stuff at low speed, but inside the wheels like that they won't get any cooling airflow over the shell like they would on a bike.

Please keep us in the loop on progress, because it's such a cool concept. I'm interested in how those controllers work out too, since I have motors that require dual controllers. Yours are out of my usual price range but they're slick.

Good luck with the project,

John

 

[litespeed]

What a cool idea.....I'm watching this one.

Tom

 

[benthomsen]

Thanks guys, I'll keep up the posts as things progress!

Cool, thanks John I will have a look through the forums regarding temp sensor install too. I do see the airflow issue, also these motors will be bolted up between two large aluminium plates, so hopefully they act as some pretty decent heat sinks to compensate. There is also the potential to create some additional airflow with a fin/fan type design on the inside the wheels mounted on the motor/rims.

The controllers do seem pretty nice too, really wanted the dual channel functionality for traction control opportunities, will see how they go once I start testing!

Cheers,
Ben