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Old 18th January 2017, 10:12 AM   #1
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Default Heavy Duty R/C Tool Box

UPDATE2: it really drives!



---------------------------------------------------------

UPDATE: It drives!



---------------------------------------------------------

So this one should be an interesting build

What is it? Why?

Basically, I go out to fly quadcopters and need to take with me:
  • spare parts
  • battery charger
  • camping chair
  • lead-acid battery to run charger - more is better
  • tools
  • marquee, for sunny days
  • water / food
  • other stuff?

...not to mention the quadcopter(s), its transmitter, batteries and other bits. Sometimes the places I fly are a bit of a walk from the car and carting all that gear suuuuuuuucks I thought about getting a wheeled toolbox, but the wheels were all way too small for grass, gravel, a bit of mud etc., and the sizes available weren't really going to solve my issue anyway. Anything suitable was going to cost an arm and a leg.

So I queued the music... and came up with:



Rofl.

I spent a stack of time working out different concepts for its design:









what even is this i literally can't even


In essence the design has / must have:
  • dual 100W 24V motors so it can push heavy loads up-hill
  • chain drive to solid rear axle
  • home-made steering servo (combine R/C servo and wiper motor)
  • 980mm length, 380mm width, 380 or 350mm height inc. wheels
  • Must fit in the boot of my Corolla without folding down the seats or removing the parcel tray
  • 8x 12v 5.0Ah lead acid batteries, for charging in the field (easily removeable so I can lift the bastard in and out of the car)
  • Powered by 16,000mah of 6S LiPo
  • SHS steel frame with aluminium checker-plate panels
  • 'roof racks' so I can strap the chair and other big stuff to the top of it with ockey-straps
  • "offroady" wheels so it can get through somewhat rough terrain
  • robust. last thing I want to do is have to carry this bastard anywhere

It's a challenging design and immediately the decision to make it fit in the boot of my car made me struggle with it. It won't have a whole abundance of space internally due to the mechanics, but it's long - almost a metre - and being able to carry things on top makes up for it significantly.

The decision to use these two small motors was a strange one but I had two reasons: 1, I already had them 2, they fit within the profile of the wheels themselves and 3, i could have gone with a worm-drive type motor for more torque / cheaper / easier but I wanted this to be quick and, more importantly, able to free-wheel so i can push it without power if need be - these motors have very little resistance when coasting.

So far I'm using these main parts:

Integrated Bot Controller to power the drive motors and the steering servo (Made by a local Melbourne engineer! Good kit.)

100w 24V DC motor x2, from Motion Dynamics - with #25 chain sprocket

12v worm drive "wiper motor" from Motion Dynamics (i'll run this on a limited PWM duty cycle so it doesn't burn out at 24v)

hand trolley wheels / axle from bunnings. I bought a whole trolley to get the axle, bearings, and two wheels, then an extra four wheels which also come with bearings for $10 each all from bunnings.

Other bits will be picked up as needed. So far I have square 12.5mm steel tube and some big bits of 4mm steel 90deg angle which I've found handy and had lying around. I'll be using rivets to attach the aluminium checker plate to the frame.
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Old 18th January 2017, 10:33 AM   #2
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So I figured I'd start the build by building the rear section with the axle, motors and everything, then the front section with the steering, then build the frame around those two parts.

I begun last night with the drive motors. It ended up being much simpler than I expected to put it together, due to the design of the hubs/bearings that come with the bunnings wheels.



I bought six wheels in total, including the two that came with the whole trolley, so that I can use the extra pair of bearings to support the rear axle and avoid having to make a fixed hub for the rear wheels.

Obviously I don't want the rear wheels to spin on the axle, so I drilled a hole through the hub and axle and rammed a nail in. I cut the nail off and banged the end flat so it can't fall out. Great! But now I can't remove the wheel from the axle... so I'll have to find a big R-clip to replace it with.



I cut a notch into the angle steel to accommodate the extra hub which I'm using as an axle bearing. It works great!





I got a suitable #25 sprocket from an e-scooter wheel on eBay. The hub is huge as its designed to bolt to the wheel, but I wanted to weld it and centre it on the axle, so I decided to weld a washer to suit the axle into the centre.



The washer was a bit big, by a mm or so, so I had to get creative to make it fit. I put it on the axle and let it spin while I held the grinder against it.



For the right-hand side, I wanted to mount the motors in and hold the hub bearing with a single bit of steel to keep the design simple. I managed to do it with a piece of angle steel the same as the left side.



The motors fit in a perfect position to line up with the sprocket, which is important for chain drive.



A test fit gave a good result



I need to elongate the holes for one of the motors so I can tension the chain properly, then attach the left side to the right, then I can begin on the steering setup.
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Old 18th January 2017, 10:49 AM   #3
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sweet little project
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Old 18th January 2017, 11:22 AM   #4
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Off to a great start.

Might I suggest lifepo4 instead of lipo? They are far more resilient to high/low states of charge than lipo. A project like this I imagine would benefit from charging up then not worrying about for the next few uses.
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Old 18th January 2017, 11:47 AM   #5
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cheers!

Gonna stick with 6S lipos as I already have them, and they should be overkill for this project really. I've heard a few things about lipos discharging but I put them at storage voltage when not in use anyway
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Old 19th January 2017, 11:21 AM   #6
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quick update

I welded the sprocket to the hub



Quick test fit to check for squareness



Next up I cut some square tube to weld in place between the left and right sides. Cut a new piece of chain to length and elongated the motor bolt holes so I can adjust the tension. Each motor needs its own adjustment as the distance on both sides needs to be a multiple of the gaps in the links, if that makes sense, it's weird working with chain...



Checked the clearance between the wheels and the motor sprockets, bolts etc... it's all very very close. I'm lucky though as so far it's all gone together perfectly.





The rear drive section is complete! (chain isn't tensioned there... need to get some more grinding bits for the dremel to elongate the holes)



Next up, I'm onto the steering section. Still waiting on postage for the motor for that, so I might paint the steel for the rear axles in the meantime. I'm not going to use any more galvanised steel as it's shit to weld, shit to paint, and releases toxic heavy metal fumes when burned which make you sick and stay in your body forever

EDIT:

Added some new parts to the list:

Heavy duty drawer slides

Continuous hinge - 915mm

2x spotlights

USB / lighter sockets / voltmeter

12v-24v DC-DC adapter

EDIT:

Got some aluminium checker plate delivered! There's two sheets there, should be enough for a toolbox, and then-some.

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Old 22nd January 2017, 2:35 PM   #7
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With the 'driving' half done, I spent the morning putting together my steering mechanism. This is the motor I'm going to use to turn the wheels. Once again from Motion Dynamics



I went with some square tube slightly drilled out to hold the king-pins for the steering



I did want to use some solid bar but it was going to take about a week just to drill all the way through one of them, so I scrapped that idea.



I bent some flat bar into a sort of U shape to hold the kingpins



The kinpins and hollow section fitted in well



I welded on some stub axles to carry the front wheels



The whole lot got put together to form the stub axles and carriers



I joined together two cut-down pieces of square tube to form a pitman arm. I had to build it this way because the output shaft on the wiper motor doesn't protude past where the bolts are



It fit nicely and you can see it just clears the bolts.



I took apart my R/C servo and got rid of the gears and electronics.





I assembled it back together and mounted it to a piece of steel along with the wiper motor, using a linkage from an R/C car for it to pickup the position



I added some linkages to the stub axles and connected it all together mechanically



There isn't a lot of angle available so the turning circle will be fairly large, but that works in my favour as it'll mean I need less room between the wheels.



Using an arduino to control the wiper motor isn't working great, using the pot as a means of position sensing. I just don't know enough code to make it work, I think it needs some kind of PID controller - it works but it overshoots the position in a big way.

At the moment I've grabbed the electronics from the servo and found a schematic. I'm going to have a crack at using the circuit to control the motor instead. It uses a BAL6686 H-bridge, which has two logic pins - one for forward, one for reverse, so it should be easy enough to interface the arduino with it.







Stay tuned for more!
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Old 22nd January 2017, 5:54 PM   #8
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Seems to work

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Old 26th January 2017, 9:26 AM   #9
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Looks like a full on build constrruction....good luck. I'll be watching on with interest to see the end result
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Old 27th January 2017, 12:39 AM   #10
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Just thought I'd share my code for the arduino I used to control my DIY servo. I couldn't find much information anywhere else on the web and ended up having to do this from scratch.

https://github.com/psYbR/arduino-servo

I had a go at building a full PID loop, which worked, but ended up sticking with just proportional control as it seemed to work best and I didn't have hours to sit and tune it.
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Old 27th January 2017, 9:34 AM   #11
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Cool Build

I'm a little curious why you didnt just get one of these and swap the esky out for a smaller one plus 'tool chest'
http://www.supercheapauto.com.au/Pro...Scooter/381072
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Old 27th January 2017, 10:36 AM   #12
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Awesome project! Definitely going to follow along.

Just a thought, if you make it big enough, could mount a seat on top and ride it out to flying locations?
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Old 27th January 2017, 2:41 PM   #13
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Quote:
Originally Posted by psychobunny View Post
Cool Build

I'm a little curious why you didnt just get one of these and swap the esky out for a smaller one plus 'tool chest'
http://www.supercheapauto.com.au/Pro...Scooter/381072
Cheers! couple of good reasons: won't fit in the boot of my car, don't want to mess around with petrol, will take just as much work to make it R/C, still need to factor in the cost ($600) on top of the toolbox and whatnot anyway. I don't think I've spent anywhere near that much yet. I already had a lot of the parts I've used so far as well

Quote:
Originally Posted by isaakk View Post
Awesome project! Definitely going to follow along.

Just a thought, if you make it big enough, could mount a seat on top and ride it out to flying locations?
that is definitely the plan
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Old 27th January 2017, 2:57 PM   #14
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I started building the frame for the toolbox



The area between the uprights is where the drawer will go. I put some flat bar in and screwed the draw slides to it



I spent a butt-load of time measuring and working out the size for the drawer, and where the wheels would go in relation to the frame



I used thick (12mm) plywood for the drawer so that I could safely screw into its edge (with a pilot hole drilled first). I also brushed on some PVA glue before joining with screws. The result was a pretty strong drawer.





Fits my quads perfectly!



I bolted a steel tab onto the rear drive section. Used bolts so I can easily remove it later



Those tabs got welded to the frame



I did a similar thing for the front as well, using the last piece of angle gal I had left over



Obviously those joints alone are not enough to take much weight, more horizontal bars will be added across the top so I can put in some vertical bars to take the weight

They were enough to give it a test run, however



It drove flawlessly! It's a bit floppy without some reinforcement so I couldn't give it the berries but it'll be damn quick. The turning circle is pretty poor as expected, but I'm not really concerned, it'll be used out on open fields more than anything
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Old 2nd February 2017, 9:00 AM   #15
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Damn wires got tangled around the split-pin on the rear axle. Woops!



Seems to have shorted and broken the motor somehow, it does nothing at all now

Took it apart to have a look (very impressed with the build quality and design, by the way) but can't see anything wrong. Anyone know how I can test it?



I used lead-free solder to re-attach the wire, hopefully to prevent it melting off if the motor overheats

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