DougM's latest build - Sand Runner

[DougM]

So only the most attentive of you will remember that right in the middle of the original build I decided to redesign the gearbox housing, but I only updated one of the gearboxes to the new housing because the other one was already complete and no sense in rebuilding it for no good reason.

Well. Now I had to rebuild it, as well as retrofit the other housing, because the mount holes for the motor covers had to move.

This is where things get weird. The outer cover didn’t change at all from the first build, but when I went to cut a new one my holes went a wandering:

The holes are the first machine op in the script, the outline is the second, so the fact that the outline cut perfectly means the machine didn’t lose track of anything, these two holes are obviously the result of bit rot.

So I re-built the job in CamBam and re-cut the part et voila! Perfection:

While that was cutting I worked on the battery tub. It has to be as waterproof as I can get it, but also the screw holes have to line up between the extrusion, the orange plastic, and the black plastic reinforcement strips. No small feat.

Lots of time was spent marking and making little fixtures to make sure all the holes aligned, but in the end it went together pretty well.

I noticed during the process of building this that the orange plastic does eventually form to the curvature I forced it into, so my plan is to leave it together for a couple of days, then go back, remove it, install the closed cell foam (told ya I was going to talk about it) between the orange plastic and the end caps to make the seal waterproof.

Another foam seal will go along the top of the end caps and the top of the extruded rails, and will seal to the wood deck. That should give me good solid IP65

Well, almost. The channels in the extruded rail are a clear and thus far unobstructed path in, so I’ll jamb those up with blobs of foam.

Next, as I said before, was replacing all the rusty screws with 316 Stainless:

Aaaaaaand we’re off to build some battery banks:

Stay tuned for next week (possibly tomorrow) when I whine about how short the leads are on the Flipsky motors. There are a number of changes I need to make to the electrical box but it’s up high on the back to keep it out of the water, and I’m concerned that in its current location it’s too far away from where the motor leads come out of the transmission.

[DougM]

So I know what you’re asking, but Doug, what happens when you don’t model every part of your assembly? Well, you put your holes in the wrong place, that’s what. In this case the holes for the Bud fittings on the bottom of the control box interfere with the extruded rail.

So I had to re-cut that piece.

Next challenge was that because a long long time ago I decreased the number of teeth in the drive gear to try to get more power the result was that the location of the motor moved too close to the truck mount

So I had to do a bit of singing and dancing to get the motor cover to not interfere with the spinney part. But they look kinda cool.

There is a pretty good chance that these are going to get broken somewhere along the line. They are Z on the height axis, which means one good smack and they’ll come apart. I will put together a new design that uses my not-patented strategy of putting a threaded almuminum rod through the whole of the Z axis so the whole things stands in compression (see my post about the control box)

But for now I’m going to let that go.

Next up was final assembly of the tub. I installed the closed-cell foam on each of the end caps

and reassembled the whole thing hopefully for the last time.

I did figure out what I’m going to do about the channels in the extrusion. One of my favorite glues, for many weird reasons, is E6000

because it holds really well but comes off clean.

I’m going to try to get it into a syringe and inject it into each of the channels to seal them up. I was going to use hot glue but once it cools it doesn’t stick very well and is likely to pop out.

Next up is completing the battery cages

And one funny story (you know, funny in a sad and frustrating way). There was a website that had a contest - design a custom housing for your Hoyt remote and if you won they would send you a free professionally 3D printed version of your housing in nylon and a complete set of Hoyt guts so you could build and use it.

I got super excited, and I actually, because I’m trying (and mostly failing) to become a Youtube sensation, recorded the entire design process, and went to enter aaaaaaaaaaand, the contest had ended a month prior.

But here’s the design - I went ahead and got a version printed and I’m going to use it on the maiden voyage of the new Sand Runner.

The thing I like about this design, and the thing I don’t like about the Hoyt, is that the circular version of the remote doesn’t give you very positive location feedback in your hand - so you have to carefully adjust how you hold it so the thumbwheel is always in the right place.

My version solves that problem, but creates another problem, which is that the remote is specific to left-handers. Or maybe right-handers. I’m left handed but I hold the remote in my right hand. I assume that right-handed people hold the remote in their left hands. Maybe they don’t.

Anyway here we are. If you look closely you can see little bumps in the remote. Those are because the Hoyt screws are too long and I didn’t realize that until they became unusually tight

[ShutterShock]

@DougM

There was a website

“a website”

Lmao idk just was funny, I thought everyone knew about freesk8

[Lionpuncher]

Love this design @DougM! Very cool. Is the stl available so one might be able to give it a try?

[jack.luis]

Finally I’ve been waiting for the revival of this project. I’ll be following

[BillGordon]

@DougM

I got super excited, and I actually, because I’m trying (and mostly failing) to become a Youtube sensation, recorded the entire design process, and went to enter aaaaaaaaaaand, the contest had ended a month prior.

But here’s the design - I went ahead and got a version printed and I’m going to use it on the maiden voyage of the new Sand Runner.

Hey Doug-

The contest is still ongoing. Please submit your design when you get a chance. I like it!

Ends April 5th:

Hoyt St. Electric - Puck Remote Design Contest

[DougM]

@BillGordon this is great news! I guess I totally misread the entry deadline

I’ve Submitted my design to the contest.

@Lionpuncher The STL’s are in the above submission, if you print the remote post pictures please.

Note that you’ll have to have a pretty accurate printer to print the inner cage. It’s a complex part. Neither of my 3D printers at home (a Lulzbot and a Prusa) were up to the task.

Thanks!

[DougM]

You remember in the movie Big Trouble in Little China when Egg Chen says, “I am the past come back to haunt you!”? Well, the decision to reduce the size of the drive gear is continually haunting me.

Turns out on assembly that the housings are so close to the truck pivot that it will interfere.

There was a point at which I seriously considered going back to the bigger drive gears, but after staring at the problem for a while I realized that maybe with a slight adjustment I could get it to fit…

Barely. (the picture is a bit misleading, there’s more space on the lower one than shows)

Once I was satisfied that it wouldn’t implode at the first turn I wired it up

And then started installing the battery banks

I powered it up and detected the motors and remote, and it is working, but I can’t charge it until I get the balance leads wired up, and I can’t wire them up until I get one more of the waterproof charge connectors (I switched from 9-pin to 7-pin but I only ordered one to make sure it fit, so now I need to order another).

That arrives early next week.

Tantalizingly close but there’s still a pretty big list

  put foam around the top of the battery box
  put grip tape on the deck
  attach the deck
  cut and install deck ends (wood pieces that cover the drops at each end of the deck)
  install the volt meter and wire it
  wire all the balance leads
  make a new balance harness for the charger
  charge it
  ride it

[DougM]

Well, from the “If It Ain’t One Thing It’s Another” department it turns out that when you attach the balance charger there’s a pretty significant capacitor discharge inrush current, which, of course, blows my balance lead fuses.

In hindsight getting fast-blow wasn’t such a good idea. And erring on the side of caution as we are doing these days I got very lightweight fuses in the first place (500mA).

So the solution is to go to slow blow, and I bumped it up to 1.5A. But now I have to wait for them to come in. But that’s ok, weather’s crap for the next 2 weeks anyway.

Overall not much forward movement:

[ ] put foam around the top of the battery box
[ ] put grip tape on the deck
[ ] attach the deck
[ ] cut and install deck ends (wood pieces that cover the drops at each end of the deck)
[x] install the volt meter and wire it
[x] wire all the balance leads
[x] make a new balance harness for the charger
[ ] charge it
[ ] ride it

[DougM]

And it’s a wrap! Literally, the last step was to wrap the cables that came out of the motor housings.

Well ok, it’s not completely done, the grip tape is still in the mail, but I can ride it without, so I’m going to take it out for a test run as soon as the sun comes back.

So just to document, here is the foam surrounding the battery tub

and here is the mess of wires that will eventually become the balance leads

And here’s a couple of glamour shots - as glamorous as you can be sitting on a table saw in a dusty shop

Oops, better put the Deck Ends on.

[x] put foam around the top of the battery box
[x] attach the deck
[x] cut and install deck ends (wood pieces that cover the drops at each end of the deck)
[x] install the volt meter and wire it
[x] wire all the balance leads
[x] make a new balance harness for the charger
[x] charge it
[ ] put grip tape on the deck
[ ] ride it

[Nacho]

Please take videos of this thing on the beach or at the sand dunes

[Fosterqc]

Hey DougM have you heard of wheeleez?

WheelEEZ Fosterqc projectie’z

[michondr]

I think this came through this forum in the past.

DougM's latest build - Sand Runner

I like the idea of the WheelEEZ- they’re a bit spendy but not totally wack. You can get the tire only for $58 ea. I’m going out to Long Beach on Sunday - we’ll see how the current 10" hard wheels work out. If they are a total bust (and 90% of the issue is sand condition) I could see swapping in a set of these. Thanks for the tip!

[DougM]

Sand runner goes out for her maiden voyage tomorrow!!! I’ll post piccies and videos.

[Plurf]

I can only hope it was so much fun that you still are ridding the beast

[jack.luis]

He rode off into the sunset and never returned

[michondr]

Seems like it

[DougM]

I’m still around, I just bit off way more then I could chew this summer. Haven’t even had a chance to get the thing back out to the ocean

[Shadowfax]

@DougM - it has been a few years. What happened to the sandrunner?

[DougM]

@Shadowfax

What happened to the sandrunner?

It’s actually running quite well, but it just doesn’t have enough battery. I can only get a couple of miles on the beach (maybe 5 or 6?) before it poops out. Also salt water is so damn conductive that the loop key port got wet and so when I went to shut it down even after I pulled the loop the volt meter continued to show voltage.

So to fix it would require a waterproof housing for the loop key and about twice as much battery. I think it’s 10S5P of 4500mAh cells. So double that - but that is a significant weight penalty.

And it’s not as fun as you’d think because the way the wheels break away on the sand is super unpredictable, so you can be turning nicely and then out of nowhere the wheels just let go.

So all in all unless you have a really strong passion for running on the sand probably your time is spent on a really nice eMTB upgrade. Like this one (which admittedly isn’t going that well).

On the other hand it turns heads everywhere it goes Here it is on a September 2023 trip