My Robot Bases
 
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My Robot Bases

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Robo Pi
(@robo-pi)
Robotics Engineer
Joined: 5 years ago
Posts: 1669
Topic starter  

I thought I'd post some photos of the robot bases I've started.   They are extremely raw at this stage, but it's what I have so here we go,...

This is the smaller indoor base for my robot Alysha

Robot Base (1)
Robot Base (2)
Robot Base (4)

The dimensions are 12" between the axles.  The plywood base is 22" long by 10" wide.  The total width is 17" to the outside of the tires.   The tires on this have 4" wheels with 10" outside tire diameter.

The photo below are the raw parts to build the outdoor base.  It will be larger and the smaller base will be able to drive up onto it and latch on to get a piggy-back ride when outdoors.

Robot Base (5)

So far all I have are some crude axle assemblies that I'm still machining.   I got the aluminum tubes from an old rowing machine.  But I need to fabricate larger axles.   This base will be larger than the base above, and will have 6" wheels that have tires that are 13" in diameter.  I laid a smaller wheel in the middle for comparison.

In the next photo I'm holding up one of the axles I'm working on.  This is where I left off.  I still  have some more machining to do just to get the axles mounted in the aluminum tubes.  Then I can build a base platform for this one, probably out of plywood like the one above.

Robot Base (7)

I'm thinking about powering this larger outdoor base with an old lawnmower engine converted to run on propane.  This larger base would also be great for a gardening robot.  In fact, I'm hoping to design it for multiple purposes.

The original idea was to carry Alysha around when she goes outside so she doesn't get her indoor tires dirty. ?  I'm think that she would also have more freedom to move around faster outdoors.  We could actually go for a stroll down the country lane.   Then when we come home she can drive off the outdoor base and have clean tires to go back in the house with.

Silly huh?

But the cool thing is that the outdoor base can end up being a robot in its own right as well.  And potentially have some gardening or yard work accessories that it can attach to when it's not carrying Alysha around.

Big Dreams!  Such a tiny start.  But first steps need to be taken before we can run.

 

DroneBot Workshop Robotics Engineer
James


   
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jscottbee
(@jscottbee)
Member
Joined: 5 years ago
Posts: 107
 

Nice work Robo. Are you going to power the wheels directly or via a belt or chain?

Those look to be good wall climbing wheels, so watch out! I speak from experience 🙁

 


   
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(@twobits)
Member
Joined: 5 years ago
Posts: 113
 

What do you have in mind for attaching a drive mechanism to the wheels?

Unless I am mistaken there is a bearing between the wheel and the axle, so you can't just turn the axle on pillow blocks. I've seen those style of wheels dirt cheap, yet plenty sturdy for a small robot, at harbor freight so they look tempting.

Maybe a small sprocket could be attached to each wheel with standoffs and bolts. 


   
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Robo Pi
(@robo-pi)
Robotics Engineer
Joined: 5 years ago
Posts: 1669
Topic starter  

I'm planning on using chain drive.   Probably bicycle chain.   Although I'm thinking of making my own sprockets.   Partly because I'm too cheap to buy new sprockets, and partly because I'd like to have total control over the actual sizes etc.   In fact, I was actually drawing up the sprockets in Fusion 360 when I got side-tracked into not being able to record what I was doing.

My idea is to connect the front and rear wheels together via the chain drive, and then just one one motor driving the wheels on each side.   Steering will be accomplished by how fast the wheels are driven.  And I'm hoping it will turn on a dime by driving one set of wheels forward and the other in reverse.  I have no clue how well it's actually going to work out in the end.  

And yes, attaching chain sprockets directly to the wheels is the idea.  The axles will be stationary.  So no need to worry about any differential axle gears.

I don't even have the axles firmly attached to the base board yet.   I started this project last winter and then got side-tracked into real life maintenance issues with my hot water heating system.   I just got this stuff out today and took these pictures.

Bill's DroneBot Forums it causing me to want to post my robot projects.  So hopefully that will help push things along.  Although, unfortunately I don't have time to work on these bases today as much as I would like to.

And yes, I got the smaller wheels at Harbor Freight and the larger ones at Tractor Supply.   If it's not cheap I can't afford to use it. ? 

I made the axles from parts salvaged from an old hay rake.   I had to turn them down ever so slightly on the lathe to fit the wheels, and then I drilled cotter pin holes on either side of the wheels to hold them in place.   On the larger robot I used rods from another piece of farm equipment that had large threaded nuts on the ends.  They fit the wheels perfectly so why not use them?

I build everything from salvaged junk. ? 

 

DroneBot Workshop Robotics Engineer
James


   
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Spyder
(@spyder)
Member
Joined: 5 years ago
Posts: 846
 

I really like the "bot in a bot" idea, plus, the salvaged junk idea must make you walk around constantly saying "hey, I can use that"


   
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Robo Pi
(@robo-pi)
Robotics Engineer
Joined: 5 years ago
Posts: 1669
Topic starter  
Posted by: Spyder

I really like the "bot in a bot" idea, plus, the salvaged junk idea must make you walk around constantly saying "hey, I can use that"

There are several reasons I went that route.    Indoors the robot needs to have a small wheel base to fit through doorways and between furniture etc.   That same base outdoors in the yard would then be quite unstable over rough terrain.  So a base with a much wider and longer wheel base will be more stable.

A second idea is that the indoor base will be driven by small electric motors as there is no need for speed.  But outdoors I would like the robot to be able to move at a fairly rapid rate.  Even potentially fast enough to keep up with me when jogging.   The outdoor base will be driven by a gasoline engine (most likely a salvaged lawnmower engine) although I plan to convert it over to propane just for neatness.   No messy gasoline.

At first I was thinking of designing a single base that could resize it's wheel base.   But that would be a lot of extra designing.   There are also two more bonuses to the two-base design.

The first, which might seem trivial but could be nice is that the indoor tires will remain clean since they will never touch the ground outdoors.  Don't want the robot tracking in deer dung.  I live in a forest and deer come into my yard all the time.   So beware of deer droppings.

And of course, having one powered by electric motors and the other powered by a gas engine is a plus too.

But then perhaps the major bonus of all is the fact that these really will be two totally separate robots that are simply capable of working in symbiotic robotic harmony when they get together. ? 

So this also means that the outdoor robot can double as a gardening robot, etc., when not carrying Alysha around.

The benefits of the two-base system are just too overwhelming not to go this route.  Easier engineering, and more benefits. Can't beat that.

Trying to build a single robot that would have this much versatility would be a far greater challenge.   Plus a single-based robot would need to change its deer-dunged tires before coming indoors. ? 

Imagine trying to engineer that one.

DroneBot Workshop Robotics Engineer
James


   
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