DougM's latest build - Sand Runner

DougM · July 7, 2020, 12:30am

The 3" Delrin rod arrived.

I decided that the most accurate way to cut it would be to CNC the top holes, which included the interface holes, so I threw it on the lathe, turned it more or less round and put a 1/4" hole in the center, then using that hole centered it into the mill.

Then just push the green button and out comes the top of the part

Then I manually turned down the other end (that will fit into the hub of the Kayak Carrier Wheels).

Here it is mounted to the truck, but not interfaced to the gearbox.

I did this 3 times. I know what you’re asking, why 3? Well, because I totally screwed the first one up and the outer bearing alignment with the inner bearing was 060 out which gave it an alarming amount of wobble. So that one had to be binned.

Also, in a moment of inattention I turned the wrong bearing OD on the wrong side, so I had to sleeve it, which wasn’t nearly as hard as I thought it would be. It’s nice to know I can save screwed up parts by sleeving them.

I 3D printed the gearbox interfaces, same as last time. I thought I had increased the distance from the interface holes to the edge a little bit but when I went to modify the gearbox interface I realized that all I had done was increase the OD of the part a little bit. Which should be fine - it was plenty strong last time (famous last words)

Anyway, I went ahead and got real rubber for the interface, so shouldn’t be shearing off any more irrigation hose. The rubber diameter is slightly larger.

I upgraded the motor cover vents from paper towels to cut-up desiccant packs which I think are tyvek

And I added a current meter but, unfortunately, the display is really dim, so it’s unlikely I’ll be able to see it in daylight on the beach.

But at least I have the sensor now, so I suppose a custom solution isn’t out of the realm of possibility

I’m waiting for a 90 degree micro-drill attachment for my Dremel so I can drill holes in the Kayak Carrier wheels to mount the hubs. It is supposed to arrive tomorrow, so with luck I’ll be back out road testing this thing by this weekend.

Then it’s back to the beach! Only this time I’m going to put something down in the car so it doesn’t end up full of sand like it did last time.

DougM · July 8, 2020, 3:08am

Managed to wrap it up tonight!!!

The tricky part was drilling the holes in the rims to lock the hubs into place. I 3D printed a fixture to drill the hole in the right place (sacrificed a heat-set insert so the drill operation wouldn’t eat away all the plastic)

then I waited somewhat patiently for a right-angle attachment for my Dremel to arrive

After that it was just a matter of pressing the hubs in, putting a screw in

and baby’s got 4 new shoes

Also, here’s a shot of the display panel. The top one is volts and the bottom one is amps

Unfortunately I’m bound after work for the next 3 days, but I hope to get it out this weekend for some grass testing.

My big concern is that the way I designed the battery pack it isn’t going to allow enough current through to push the motors and it will generate a lot of heat.

That’s what the Ammeter is going to tell me.

After that, assuming all goes well, it’s a trip to the beach for me.

Plurf · July 8, 2020, 6:30am

Those wheels looks funny on this board, are they sturdy enough to widstand thr weight and vibrations ?

Curious to ear of the in situe tests

Flexboardz · July 8, 2020, 9:09am

Congratulations for all your work.

I’m very curious to see how the wheels will handle the job.

What kind of wheel is it exactly? (there are some golf cart wheels that look similar).

It’s probably the way to use larger wheels without being too heavy to be ridden…

DougM · July 8, 2020, 3:09pm

@Plurf, @Flexboardz,

They are kayak carrier wheels - they are surprisingly tough and lighter, with a bigger footprint than the rubber tires. I too am interested in how they fare

They are rated at 500 pounds each, so no problem carrying my weight.

Flexboardz · July 8, 2020, 4:00pm

Thanks.
Looking forward for the test…

ZachTetra · July 8, 2020, 4:11pm

What’s the diameter and contact patch? My friend wants to ride her MBS board in the beach and this looks like a mod I can do

DougM · July 9, 2020, 2:03am

10" Dia, 3.5" width, but since they aren’t inflatable the contact patch isn’t that big - but since they are flat edge to edge I think it’s a lot better than a rubber tire, which at that size seem to bulge in the center.

Much more important, I’ve found, than the tires is the sand condition. The first time we went out it was on my mountain board, which has 8 by ~1.5 standard mountain board tires and it worked great, because the sand was heavy and wet and a much larger part of the beach was wet.

The most recent time we went out, to test this board, it was soft and damp, and most of the width of the beach was dry sand.

There’s no way you’ll get over dry sand without 4WD and even then it’s iffy. Soft wet sand isn’t much better. So whatever conditions cause the sand to be heavy, wet and wide (low tide maybe?) are the best conditions.

maxmayer · July 9, 2020, 2:16am

may be a little late to this… but check this out:

there is a thread dedicated to it

Plurf · July 9, 2020, 6:35am

Why not caterpilars ?
@Flexboardz
with a similar system to the flexboard it could work

Flexboardz · July 9, 2020, 7:06am

“with a similar system to the flexboard it could work” …in theory and in straight line, it should work but I don’t know what will happen when leaning/turning… (there are some rubber caterpilar that are quite light/flexible).

I have few sub projects about the E-Flex like AWD, larger wheels, balance control, ice blades or ski…but not yet caterpilars…

DougM · July 9, 2020, 3:17pm

Seems like the best solution to soft sand is horsepower, 4WD and big paddle tires. The problem is that the machine becomes really heavy because of the amount of battery you’d need.

I tried to drive the Sand Runner into the soft sand with no rider (just the board) and it bogged down immediately and just spun the back tires.

I’m ok with only riding on packed sand, that’s the most fun anyway because it’s tangentially similar to snowboarding (you can kick the back out, etc.), but I wasn’t expecting the beach conditions to be so variable. Now I’ll need to look at the tide tables when planning my trips.

I worked on a flexboardz like design for a while - I might come back to it since I’m fundamentally unhappy with skate truck based mountainboards, but that’s a project for another winter

DougM · July 10, 2020, 12:09am

Thanks for the pointer - I did manage to get a FocBox for this build. If it works ok I’ll probably get another one

magharees · July 11, 2020, 10:45pm

I have this nagging feeling that you would do better with MBS T2 type tires on hubs running on soft sand. Consider getting some MBs five stars and the T2 9” when @tinp123 gets to be GB.

Really enjoyed the build thread nice going

DougM · July 12, 2020, 2:59am

My first test was with 10" hand truck tires

and that didn’t cut it. It seems like the contact patch on a 9" tire would be even smaller.

I’ll let you know how these new wheels do.

DougM · July 12, 2020, 3:02am

So I got the board out to the park for its first field test with the new electronics and the new wheels and everything feels solid - much more power and the wheels didn’t fall off.

Here is a video of a test run through the grass

Next stop - the beach! But not until next weekend.

magharees · July 12, 2020, 3:19am

I saw it and read enough to forget again

I think you can make whatever you need which is a nice position to be in…there could be a weight vs tyre pressure vs sand cohesion vs speed thing going on.

Hopefully I’ll have some comparative data in a month or two on some other setup choices

Dareno · July 12, 2020, 3:59am

Oh sand. It gets everywhere and stays there. Add salt into the mix and recipe for disaster. All you can do is a strip down and clean after every ride and still you will find sand somewhere for the next 2 weeks. What a build this is man seriously. Absolutely brilliant read. Riding on sand you either need lots of power and paddles or you go low pressure tyres. The thing that gives you traction is not width its length of contact patch so by lowering the pressure the tyre has more area driving you so a larger diameter tyre will have more effect than a big old fat one.

I am loving this thread keep up the awesome work brother.

glyphiks · July 12, 2020, 4:40am

Holy shit. Been a while since I popped in here, you have been hard at work!

This is fucking spectacular! BOTY contender for sure!

taz · July 12, 2020, 4:52am

I can’t believe this is the first time I notice this thread.
Whole lotta work and ingenuity here.
Congratulations sir.