"Monster Board" High power 4X4 board with ATV tires

Lightweight / Folding / Portable EVs - seats optional
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"Monster Board" High power 4X4 board with ATV tires

Post by recumpence » Jan 06 2018 8:00pm

Hey Guys,

As the title suggests, I am beginning my latest build that I am calling the "Monster Board".

This will be a huge skate board. It will be over 4 feet long and 28 inches wide. The wheels are 13 inch kids ATV tires. It will be four wheel drive using two Astro Flight 3210 motors (one per axle). It will be live axle (no differentials). For a street board, solid axles do not work well. But, for an off road application, they work great! The board will have full suspension with 4 to 5 inches of tavel and 8 inches of ground clearance. It will have a total system power potential of nearly 10,000 watts! It will be geared for 15 to 20mph depending on how well it runs at verious speeds. This means it will have crazy torque! The pack will be 6S, 40ah Multistar Lipo running through two Castle Creations ESCs. The axle assemblies (trucks) will consist of go-kart axles, hubs, sprockets, etc. I am building this as a true all terrain board capable of going pretty much anywhere, including snow. Odds are it will not be running this winter. But, I really want it for next year. I plan on being able to tow my son around behind it..... :mrgreen:

Make no mistake, it will be a BRUTE! I expect it to weigh upwards of 75 to 80 pounds. It will be, essentially, a 4X4 go-kart slightly shrunk down that you stand on a lean to steer.

For those of you familiar with my E-bike drive systems, this board will use two of my DaVinci Drives. The motors will run up at 10,000 RPM spinning a toothed belt to a jackshaft, then a #35 kart chain from the jackshaft to the axle. The front and rear axle assemblies will be identical running their own independant drive system.

This is a project I have been thinking about for a few years now and I am finally pulling the trigger on it.

So far I have the following parts in hand;

Wheels
Heim joints for the suspension
Air shocks
wheel hubs
DaVinci Drives and system parts
misc aluminum and steel for the suspension and chassis

I have the following items on order for it;

Axles
motors
ESCs
misc materials

I am guessing it will take around 6 months to get it running. So, be prepared for a long wait. I have a couple huge OEM projects for clients that are taking up most of my spare time. But, I really want this thing running! This is one of the very few projects my wife has shown an interest in. :D

I will post pictures as I have them.

Matt
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Re: "Monster Board" High power 4X4 board with ATV tires

Post by recumpence » Jan 10 2018 5:23pm

Here are a few pictures.

The tires are 13 inch diameter. I am using standard go kart hubs. I drilled the rims to the hole pattern for these hubs.

The suspension will consist of custom double wishbones using 3/8 heim joints and mountain bike air shocks.

This build will probably take 6 to 8 months because I have two large OEM projects taking up most of my spare time.

Matt
Attachments
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Wheel
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Hub
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Hub on wheel
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Wheel on axle
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Suspension parts
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Re: "Monster Board" High power 4X4 board with ATV tires

Post by recumpence » Jan 10 2018 10:02pm

In the pictures you can see I am holding a solid 1 inch axle. That is a standard go kart axle. This board needs two of them. Those things are freaking HEAVY! I am guessing they are over 10 pounds EACH! So, I ordered some hollow one inch 6061-T6 aluminum tube to make my own axles. That should shave at least 15 pounds off the weight of the board.......

Matt
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Re: "Monster Board" High power 4X4 board with ATV tires

Post by Sean9002 » Jan 16 2018 10:57pm

Sub'd....this is gona be good :D
OSET 20+ - Custom frame and swingarm, Motorims - 66V
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Re: "Monster Board" High power 4X4 board with ATV tires

Post by recumpence » Jan 17 2018 2:33pm

IMG_20180117_1392.jpg
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A couple "Monster" controllers for the Monster Board! :mrgreen:

Matt
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Re: "Monster Board" High power 4X4 board with ATV tires

Post by recumpence » Jan 17 2018 2:38pm

Here you can see the original steel axle next to a hollow 6061-T6 aluminum axle I made. The steel axles weigh in at 7 pounds each while the aluminum axles weigh 1.3 pounds each. That is a savings of 11.4 pounds just in the axles! I have also decided to drop the pack size to save more weight. I was planning on running four Multistar 6S 20ah packs. However, I am dropping that to two packs because it looks like the range from those four packs was way beyond what I need. That reduces the weight of the board another 11 pounds (over 11 pounds)! So, the new axles and different pack size drops the overall weight of the board by nearly 23 pounds! :mrgreen:

Matt
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Re: "Monster Board" High power 4X4 board with ATV tires

Post by litespeed » Jan 18 2018 7:42am

Sounds like something I could get hurt on......I want to see this.

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Re: "Monster Board" High power 4X4 board with ATV tires

Post by GeriatricGeoffrey » Jan 18 2018 6:06pm

okay... shut up and take my money!

how much did the aluminum replacement set you back? you have your own machine shop? :D

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Re: "Monster Board" High power 4X4 board with ATV tires

Post by recumpence » Jan 18 2018 7:00pm

The aluminum tube was $20 for enough to make two axles from online metals.

I have a few hobby milling machines, lathe, TIG welder, MIG welder, plasma cutter, and the usual drill press and various tools.

You can search my projects in the Non-hub bicycle section to get an idea of what I build.

Matt
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Re: "Monster Board" High power 4X4 board with ATV tires

Post by recumpence » Jan 20 2018 12:19pm

Here is one of the two drive units. There will be two of these, one for the front axle and one for the rear axle. Each unit is 5,000 watts. Geared for 15mph with 10,000 combined watts available, this thing should be able to tow a car...... Literally.......

For those of you who are unfamiliar with my bicycle drive units, this is a baby version of what I build for bikes. It is a toothed 5mm pitch belt to a jackshaft. Then it will run a #35 chain to the axle. The motor will run around 10,000 rpm at full throttle. So, it will be geared very low to the wheels to achieve the 15mph to 18mph top speed I am looking for. That will provide huge torque to the wheels for good off road power.

The large hex nut in the center of the big pulley is the torque limiter. This part will allow some slip at high load to protect the drive-line.

Matt
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Re: "Monster Board" High power 4X4 board with ATV tires

Post by recumpence » Jan 20 2018 4:37pm

Wow, no questions?

I have identified a few areas that are of concern when building something like this;

#1 Weight (this is why I have been making a strong effort to lighten it up).
#2 Bump steer. With track width like this bump steer becomes a major problem. So, each axle will have its own steering damper.

Matt
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Re: "Monster Board" High power 4X4 board with ATV tires

Post by SlowCo » Jan 20 2018 5:23pm

Great project again and having seen your previous builds here on E-S I look forward to the craftsmanship on this "Monster Board"!

What I have been wondering about with a solid, non-differential driven axle is the resistance in turning/steering. As you write it won't be such a problem off road but would be more prominent on paved surfaces with more grip. Normally a differential would allow the inner wheels to slow down so they don't resist turning the vehicle. What if you would use these type of freewheels (LH&RH orientation) on the axle ends:
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and attach the wheels to the outer flanges? That would allow the the outside wheels to rotate faster than the driven speed in a turn and let the solid axles act as a differential setup. I've always wondered if that would improve the handling of a drive system like this. Just an (silly?) idea...

Good luck building, I'll be watching your progress.

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Re: "Monster Board" High power 4X4 board with ATV tires

Post by recumpence » Jan 20 2018 7:12pm

Yup, I have considered it. Honestly the only reason I am not going in that direction is complexity. One major issue becomes brakes. With live axles, I can use the electric brakes in the controllers. :D

Glad you pointed that out, though.

Matt
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Re: "Monster Board" High power 4X4 board with ATV tires

Post by recumpence » Jan 24 2018 7:06pm

More progress.....

Here you can see the process of building suspension arms. Shown is the lower arm. There will be two of these arms, one in front and one for the rear. The suspension will be double wishbone. However, the wishbones who not be oriented out the sides of the deck as they would be in a car. They will be protruding from the front and rear of the deck. The solid axle trucks will be hung from the suspension arms.

Matt
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Re: "Monster Board" High power 4X4 board with ATV tires

Post by recumpence » Jan 25 2018 8:43pm

I made quite a bit of progress lately. I thought this project would go slowly. But, at this point, it may be a month or so to finish!

I finished both lower suspension arms and much of the frame (deck).

Keep an eye on this thread. I will be posting progress pictures this weekend.

Matt
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Re: "Monster Board" High power 4X4 board with ATV tires

Post by SlowCo » Jan 26 2018 8:44am

Great work. And you're right about the added complexity of individual brakes at all wheels when using freewheels.
I do hope this board will inspire you to build a 2.0 version with a separate drive unit (4x5kW :shock: ) and brake for each wheel :twisted:

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Re: "Monster Board" High power 4X4 board with ATV tires

Post by recumpence » Jan 26 2018 1:11pm

I know what you mean. I was really close to going that route. However, there were a couple of things holding me back. The first thing is the added cost of two more Motors and two more controllers. Basically the overall cost of the board would increase upwards of $1,800 or so. Beyond that, I only have two of these smaller Drive systems in stock. I have one other small one that's a different style. So, I have two matching Drive systems and it's far cheaper to build it this way. So, that gave me the direction to go in. Also, this way is lighter. And, four Motors would be far more power than would ever be used. Anyway, it would look amazing, and it would be phenomenally high-tech! I have an oem client that I do production work for who is interested in possibly purchasing this board from me. If they purchase this board from me, I may go the four motor route on the next board. Also, if that happens, I may go with full size ATV tires on the next board. It all depends. Anyway, I think larger tires may make standard lean steering very cumbersome. I have a feeling these 13 inch ATV tires are about the largest I could go and still make it handle like a skateboard / snowboard.
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Re: "Monster Board" High power 4X4 board with ATV tires

Post by ElectricGod » Jan 26 2018 4:30pm

I love your suspension. As soon as I saw the shock on top of the arm, I realized what you were doing. This board is going to have soooo much travel in the wheels. I can see you jumping up and down on the deck and getting 4" of travel or more. I'm really curious to see how those ball joints hold up. With only 2 wish bones, how are you going to steer? Will the front wheels pivot? Will you put trucks under the suspension so leaning creates angle change? Is that what you meant?
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Re: "Monster Board" High power 4X4 board with ATV tires

Post by recumpence » Jan 26 2018 9:39pm

Good question.

The picture is of the lower control arm only. There is also an upper control arm. So, this is a double wishbone suspension system. :D

This will be a normal lean street system. I am fabricating a large scale version of standard skate board trucks. The suspension arms will terminate into mounts that will hold the trucks at their normal lean steer pivot angle. It will become clearer when I post more pictures.

You are correct, there will be high travel. I am shooting for 6 inches of travel. It will have around 10 inches of ground clearance.

Also, there will be steering dampers at each truck minimizing bump steer. That being said, with wide trucks, and the high amount of articulation as well as the suspension travel, it should be good for some seriouly rough terrain. It should climb up curbs without a problem.

Matt
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Re: "Monster Board" High power 4X4 board with ATV tires

Post by recumpence » Jan 27 2018 1:18pm

Here is the basic frame with suspension arms installed. You can see it in front of a table in my office. That will give you an idea of scale.

Overall length as shown is just short of 5 feet. The frame is 1.5 inch box section aluminum (1/8 inch wall). The suspension arms are 3/4 inch box section steel (1/16 inch wall). The Heim Joints are 3/8 inch.

I have been practicing my TIG welding. Most of the welds are looking pretty good. All welding of steel and aluminum has been done with the TIG. I am trying to go away from MIG welding as much as possible.

Matt
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Re: "Monster Board" High power 4X4 board with ATV tires

Post by recumpence » Feb 03 2018 2:51pm

Progress!

I have been working hard on the board. I have about 8 hours in it this week.

You can see the suspension is mostly done. It has a touch over 4 inches of travel. I was originally hoping for closer to 6 inches. However, with the clearance I have, this is best. Also, these shocks were designed for 4 inch travel suspension. Going up too much would require far higher air pressure in the shocks and that is not a good thing.

Standing on the board is really interesting. Leaning forward squats the front end down. I think adding suspension to a lean steer vehicle like this will add another dimension to the riding experience beyond just smoothing the terrain.

You can see the scale of the board with my 14 year old son standing on it. I purposely mounted the upper suspension/shock mounts at a 45 degree angle so they can double as angled foot plates.

This thing will have crazy bump steer issues with the 32 inch wide trucks. So, I ask installing motorcycle steering dampers at each end. This should reduce bump steer while adding a degree of tunability to handling dynamics of the board.

In the one picture you can see me holding a loose Heim Joint next to the top spock mount. This is for the upper control arm. Remember, this will be a double wishbone system.

One thing about this build that is kind of frustrating; just about every part on this thing has to be made. Normally my builds consist of a bunch of industry standard parts with a few custom bits thrown in to complete it. However, with this board, every bracket, every spacer (heck, even most of the bolts) are either made specifically for this project or drastically modified to work. Making so many individual parts takes alot of time.

Matt
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Re: "Monster Board" High power 4X4 board with ATV tires

Post by recumpence » Feb 04 2018 2:58pm

More progress photos.

Today I modified go kart wheel hubs to be used as sprocket carriers. I modified two identical parts (ones for each axle).

If was a simple matter of starting with the rotary table on the milling machine and finishing up on the lathe.

Again, every single part on this build has been either custom made our highly modified.

Matt
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Re: "Monster Board" High power 4X4 board with ATV tires

Post by recumpence » Feb 09 2018 5:54pm

More progress......

The suspension is finished. You can see the upper control arm and the upright have been made (front and rear suspension is finished). The upper control arm can be adjusted to change the steering pin angle.

As I mentioned before, every single part for this thing has to be made or modified. It is really coming along, though. I have not really had any issues or system redesigns come up. It is just coming together as planned.

Matt
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Re: "Monster Board" High power 4X4 board with ATV tires

Post by recumpence » Feb 14 2018 5:56pm

More progress.

Here is the truck steering assembly. The pivots are ball bearings.
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Re: "Monster Board" High power 4X4 board with ATV tires

Post by recumpence » Feb 14 2018 5:58pm

Here is the setup I used to get the geometry correct. You can see I used a level on the deck and a carpenter square as a reference.
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