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Ramp walking toys #1: Return of the Wombat

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Blog entry by Tony Slattery posted 06-05-2015 01:03 AM 2881 reads 2 times favorited 9 comments Add to Favorites Watch
no previous part Part 1 of Ramp walking toys series Part 2: the man who started it all - Tad Mcgeer »

A short history of my journey into the art and craft of making ramp walking toys. Also known as passive dynamic walker.

As much as I like making things, enjoy making things that move even more.

It all started with the Ramp Walking Rhino, a design by Robert Lou Ma. I made one, and it kind of worked. I think the problem was a small hinge, which I did not have, so I used a piece of piano hinge instead.

The challenge with these toys is to minimize friction, and the hinge was not sturdy enough to prevent the back leg rubbing on the body.

Tried making a different kind of hinging mechanism, but that ruined the geometry and I lost interest.

Enter the Wombat

No hinges in this one, and I recently bought a scroll saw, so this seemed to be a good pattern to practice on.

It worked pretty well this time, but not being able to leave well enough alone, decided to figure out how and why it worked. If I can observe and describe the action, then I have a better understanding of how it works.

So here goes:

Made a copy in AutoCAD and pin pointed the centre of mass of the body in relation to the pivot point and the centre of mass of the legs, as shown in the image below.

Using movie maker to pause the video and take a screen shot, cropped each frame to remove the background distractions.

Frame 1

On the horizontal, this is the natural resting position. On the ramp, give it a little shove and it starts walking.

Frame 2

The legs have hit the back stop and it is about to tilt forward.

Frame 3

On the front paws, about to tilt just a little more to allow the legs to rotate forward. If the ramp is slightly too steep, it does in fact tilt onto it’s nose. Makes me think the front paws need a little modification.

Frame 4

The legs have come forward, and it is about to tilt backwards.

Frame 5

Tilting backwards and the tail hits the ramp. Starts to slide forward.

Frame 6

Starts all over again – very much the same as frame 2 – The legs have hit the back stop and the tail is lifting off the ramp.

Frame 7

Same as frame 3 – on the front paws and the legs about to swing forward.

And off to see the wizard. If there was a ramp long enough, it would carry on forever, which has given me another idea.

-- Tony, Australia, http://www.wooden-toy-plans.com/



9 comments so far

View Pimzedd's profile

Pimzedd

562 posts in 3270 days


#1 posted 06-05-2015 01:36 AM

Been thinking of making some of these myself. Hope you post any follow up work.

-- Bill - Mesquite, TX --- "Everything with a power cord eventually winds up in the trash.” John Sarge , timber framer and blacksmith instructor at Tillers International school

View crowie's profile

crowie

1497 posts in 1417 days


#2 posted 06-05-2015 03:53 AM

Top blog Tony thank you,

But the heading & the subject matter don’t line up….Wombat & kangaroo/wallaby??

-- Lifes good, Enjoy each new day...... Cheers from "On Top DownUnder" Crowie

View stefang's profile

stefang

15512 posts in 2800 days


#3 posted 06-05-2015 08:07 AM

Pretty cool. I can see the little ones having a lot of fun with these, and without batteries!

-- Mike, an American living in Norway.

View Tony Slattery's profile

Tony Slattery

76 posts in 561 days


#4 posted 06-05-2015 10:46 AM


Top blog Tony thank you,

But the heading & the subject matter don t line up….Wombat & kangaroo/wallaby??

- crowie

Deliberate mistake to see if anyone is paying attention ;)

-- Tony, Australia, http://www.wooden-toy-plans.com/

View robscastle's profile

robscastle

3392 posts in 1670 days


#5 posted 06-06-2015 08:46 AM

You are a Wombat!

Deliberate Mistake indeed ….Fair suck of the sausage

-- Regards Robert

View JoeinGa's profile

JoeinGa

7483 posts in 1473 days


#6 posted 06-06-2015 02:06 PM

Neat little toy!
Welcome to LJs !

-- Perform A Random Act Of Kindness Today ... Pay It Forward

View Tony Slattery's profile

Tony Slattery

76 posts in 561 days


#7 posted 06-06-2015 11:04 PM



You are a Wombat!

Deliberate Mistake indeed ….Fair suck of the sausage

- robscastle

Naughty, naughty, not that kind of wombat. Thought it was fair suck of the sauce bottle, compliments of our illustrious PM.

-- Tony, Australia, http://www.wooden-toy-plans.com/

View WoodNSawdust's profile

WoodNSawdust

1417 posts in 642 days


#8 posted 06-07-2015 12:46 PM

Thanks for sharing.

I am not familiar with ramp walking toys, in this toy am I correct in assuming that both feet are glued to the dowel that privets freely in the body’s hole.

-- "I love it when a plan comes together" John "Hannibal" Smith

View Tony Slattery's profile

Tony Slattery

76 posts in 561 days


#9 posted 06-07-2015 10:57 PM



Thanks for sharing.

I am not familiar with ramp walking toys, in this toy am I correct in assuming that both feet are glued to the dowel that privets freely in the body s hole.

- WoodNSawdust

Good question – see the image below:

Removed one leg to show the mechanism – no batteries!

The original used dowels, to reduce friction to a minimun in this experiment I used nails. If it is to be for a child, dowels would be better.

The red dot is the pivot point, able to rotate freely in the body, press fit in the legs.

The blue dot is the nail (dowel) that links the two legs. The green lines are the front and back stops to limit the rotation of the legs.

The yellow circle is a dowel washer to keep the legs from rubbing up against the body. It is not attached to the body, it fits onto the red dot nail.

In production I would use a drill press to drill the holes for the dowels, because you want to make the holes perpendicular. And make plastic washer/spacers.

Hope that helps to explain.

-- Tony, Australia, http://www.wooden-toy-plans.com/

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