Jansen Walker Toy (sized) Bot

Community General Discussions
, , , , ,
1

Hello everyone,

This is my first post here, don't be rough.

I stumbled on the this site about a month ago while doing research on a bot i'm building that's similar to Rik's current Jansen Leg project, that's actually what I was searching for when I found the site.

Anyway, I wanted all of you input on my project, my version uses a similar leg design and I'm curently planning on powering it with two servos and an Arduino-clone.

I'm trying to decide on the size, either a medium sized bot that would be about 8 inches in height and width, or a tiny 3in version. There would be lots of space for sensors on the big one, very little space on the small one.

The obvious drawback to the big one is the cost of materials, it actually uses about 10x as much since the parts are bigger and thicker. The little one would be cheep to have cut, but would only have space for one or two small sensors.

I plan on making the plans publicly avalible to anyone that wants to build their own, which one would you like to see?

2

I’d build the bigger one

I’d build the bigger one because:

a) My limited experience of robotics has shown me that construction material is far cheaper than electronics or drives

b) It’s easier to work in a large space than a small space - so frustration will be lower

Reasons for a small bot are:

a) Small is cute - noise0 proves this again and again (although big is macho)

b) There’s less mass to move so there might be big savings on the drive train

3

Escape

I had to hit ESC on my keyboard to stop being mesmorized by the animated gif. Now I can type again.

And think.

I agree wit Mike and Oddbot. Size does matter. For example: in my experiments with pivots, I found that plywood of 3.6 mm is almost impossible to work with. The joints (pivots) would not be strong or durable or tight or simple. When I upgraded to 6 mm (and better quality) plywood, that problem dissappeared. I cannot imagine making my legs smaller with the same material. "The only way is up."

BTW, my legs now measure about 25 cm (10 inches) from the floor.

Turns out that the enabling technology for my vehicle is in the pivots. They now dictate the use of material and size of the whole machine. Or the other way around: the only thing I need to miniaturize my vehicle, is better a pivot technology. Or lower my expectations towards load bearing capacity…

4

not a dupe
Don’t worry about duplication. Not here on LMR. I am looking forward to updates on your project. At least provide us with (more) links to your (beautiful) blog.

5

Update

So I updated my plans earlier tonight to make a medium sized version and fired up my laser cutter. This version is about 5 by 4 inches and seems like a happy medium in terms of size. I think i’ll be able to use 2mm plexi-glass for the materal and the entire bot can be cut from a single 200mm square. (The biggest I can cut with my laser).

I’ve started with using 3mm bolts as the joints, they seem to work good enough for testing though getting a good lock is kind of tricky without tightening the bolt down too much.

So far with this prototype I was able to get one leg working pretty well along with the central base, i’ll need some minor adjustments before I can put the whole thing together. I’m amazed at how 1-2mm adjustments make a big difference here.

If you have any ideas or criticisms let me know, I’m still open to any new ideas.

Here’s a coupe pics of this first try for your enjoyment…

Pile of random parts:

1 Working leg:

Base with arduino in place:

Base with both sides visable:

6

AWESOME! this looks so
AWESOME! this looks so professional, I can’t wait so see it move

7

**What **

laser cutter do you have?

And also how do you guys plkan on stearing these things?

Excelent build quality and a great write up on it mate.

8

CNC envy

Wow, some result for firing up a robot and waiting for the parts! That would have taken me a long night at the jig saw. I’m anxious to find out how your 3 mm bolts are working out for you. Did you ever consider smaller ones?

Did you consider lock nuts. I could not find any that small in my hardware store. Others have suggested liquid fastener for bolts. Brand names will vary.

9

Materials

I’ve got two basic choises with plexi-glass: 2mm which is only about $1.50(US) a perfectly sized sheet that I can stick right in my laser. The other is 6.5mm thick and costs about $20.00(US), but has to be cut down by hand into 6 peices to fit in the cutting area.

There’s also a fiberboard wood that I’ve been toying with that’s 3.5mm, but it’s not as attractive as the acrlic. You can however get an 8x4 foot sheet that would make many robots for only about $10(US).

I guess either of those options won’t break the bank, but I’ve been toying with the idea of selling inexpensive kits of the mechanical parts, I think that would be pretty cool.

10

Bolts

I’m going to reserve final judgment on the 3mm bolts until I get the whole thing together, but my first impression is that they will work. I do need to find some kind of locking washer like you say, I was hoping that I would be able to get away with just tightening two bolts together, but it’s not as easy as it seems.

Having the laser around is awesome for this kind of project, it really makes it easy to turn out prototypes. The downside is you have to spend a considerable about of time drawing all the parts in a CAD program first. I’ve found that SolidWorks is great for mechanical stuff, but has a pretty steep learning curve.

11

Laser

I have an older version of the Artsign JSM40: http://www.artsign.com.cn/Productinfo.asp?id=56 it’s desinged for cutting signs and engraving trinkets. It also has some serious limitations compared to the big expensive ones like Epilog makes, but the price diffrence is also huge.

It’s a pretty common one on ebay, I got mine used.

12

Opps

I just realized that link is no longer good, here’s an updated one:

http://www.artsign.com.cn/Productinfo.asp?mun=Laser%20Engraving%20and%20cutting%20machine&id=167

13

I might
Save for one, they look really handy.

14

Update 2

I’ve cut and mostly assembled the 2nd prototype, the design is getting very close to being finished.

This go around I added a battery storage area, and offset the driving servo so that gears can be used for turning the main drive shaft. I’m not sure what ratio I’ll use yet.

There are still a few flaws that I’ll need to fix, but ingeneral the design is very close to being finished.

Here are more pictures:

 

More Cut Parts, enough to build one walker:

 

The new battery compartment seen from the top:

 

Battery Compartment and servos seen from the bottom:

 

Base with Arduino mounted, I used hex stand-off nuts to keep the bottom of the board away from the other base mounting screws:

 

The main body seen from the side, so you can see the layers of construction:

 

A working leg pair, there will be one of these on each side, the legs are heavier then I expected with all the bolts and nuts required to tie them together. I may need to find smaller bolts for the extraneous joints. I’ll also probably need to find some kind of rubber cap to put on the feet, they have very little traction.

 

One pair of legs on the body. Unfortunately the driving gear did not fit on the servo horn, so I will need to cut a new one:

15

really nice

and blog worthy

Please post a photo from dead above, looking down on the legs. I would like to see how the layers of plex relate. Especially around the crank nut (which I call V).

16

I second (or third) the envy
I second (or third) the envy on the laser cutting. Those parts look just great.

17

Above

Here is a picture from the top, it kind of hard to tell whats going on since all the layers look about the same from that angle, but i’ve put some notes on this one:

18

Gears

So I’ve been kind of treating this thread as a dump for status updates on this project, if that’s the wrong use of the forum please let me know.

Anyway, I spent most of last night designing the gears that will link the servo to the drive train, I’m hoping that a 1:1 ratio will be okay, the servos are surprisingly strong for how small they are.

By far the hardest part was getting the teeth on the inside of the servo gear just right, I wanted to just slip the gear onto the servo horn and have the teeth grip the ridges that are on the horn for gear traction. I was not sure if my laser could cut 15 teeth around a 4mm hole, that means the inside teeth are only about 0.5mm across! I was pleasantly surprised to find out that it could with exactly the right focus and power make a gear that grips the servo horn pretty well.

The teeth on the servo are so small that I had trouble counting them, I swore there were 16 the first 3 times I counted, but it ended up being 15.

Both gears will be 2 layers of plexi, one layer grips for rotation, the other stops movement along it’s axis. The two layers are glued together to make somthing usable.

Here is a shot of my test material, a standard playing card, you can see the servo horn teeth well:

 

Here is the first working acrlic gear, on the servo:

Here is both gears together, note the screw that holds both in place:

I just realized I did not not take a picture of the other gear set, it was designed to fit around the nut of a 3mm bolt, and in comparison was pretty easy to design.

For my next prototype I think I’ll try 2mm bolts on most of the parts of the leg, I think they are about half the weight as 3mm. I looked for alternatives like plastic ones at the hardware store, but they don’t carry those kinds of things around here evidently.

19

You’re right

That is hard to see. The transparancy does not make it any easier.

I did notice the spacers and extra nuts. My legs are designed as “floors of a building”. Not a single floor is diagonal. Do I notice a few “diagonals” in your legs? That is, members that run from one layer (counting from the support layer) to another?

20

third

CNC envy

Not so much envious about the 200x200mm restriction though. I would love to cut 12 parts from one sheet in one go.