Tribute to fritsl's Trata

After looking through some of the robots on this site, seeing the videos of Trata, and then looking out of my office window to see the dwindling remains of 4' of snow, I decided to take action. On Sunday, intending to do something productive in my workshop, I found a nice length of PVC and some bookshelf brackets, and this project was born.

I have been flying R/C for several years and have a few old planes that I can pull parts from. For better or worse, all of my engines are glow fuel powered...and so is my little snow sled.

Following the comments from Trata, I build this to be fully steered by thrust - no rudder.

Last night was the first test run. After 4 years of non-use, the little glow engine sprung to life and provided more than enough power to pull the sled along. After several adjustments...and then a couple more...the sled kept trending to the left.

I think I'll add a rudder to see what difference it makes.


As said before; Cool idea to

As said before; Cool idea to bend the tubes, and I hope to see a video, it looks very inspiring.

I wonder why it goes to a side - of course the propellar is set up to pull down the left side, but that should not have that kind of an impact?!

What does it do if you just give it a push / let it go down a hill?

Thanks for reposting :wink:

Good Idea

As soon as I get a chance, I’ll run it down a hill and see. I think it will stop…so I’ll have to push hard. =)

Happy to repost here, but, it is on a path to becoming a robot. Once I am happy with the frame, I am going to mount a Xbee radio, an Arduino, and then see what good it does. That update might have to come next winter. Then again, they are calling for more snow this weekend!

Oh, and what do you mean - “pull down the left side”?

The motor / propellar is not

The motor / propellar is not only moving air backwards, it is also moving it around the axle, and pushing the machine the other way around same axle :slight_smile:

You shoult take a candle, and rub it against the sledges, till a layer is left on them. That will make it slide over the snow without problems!

Got It

Okay, that’s what I thought you were referring to. Working on some code for another (real) robot. Once I get that working, I’ll switch back to the sled.

And thanks for the wax tip - I already have some on my bench waiting.

Torque and Newton

Every action [blah] reaction. Propeller and motor are pushing each other in opposite directions, by equal measures.

Air planes suffer from the same deal, but they don’t keep their skis on the ground for very long. Consider relocating the propeller off centre to compensate.

Ah, my mistake…

I forgot to mention that this thing runs at relativistic speeds. Newtonian physics are out. :wink:

We need to know how it
We need to know how it glides without motor on!! You!

My Bad…

It was a busy weekend…I did wax the sledges though (boy does that sound bad), but didn’t get it outside.

Maybe I can do it during a coffee break tomorrow.

Unpowered Test Results

First of all, the wax made a HUGE difference. Thanks for the tip!

BUT…unpowered, it still tracks left. And it doesn’t take very far to see how evident it is.

The sledges are toed in just a little bit. Rationale? Well, with R/C planes, I was always told to toe in the landing gear just a little to help it track straighter. Plus, the “snow plow” is a pretty stable stance for skiing.

At this time, there are two things I am thinking of trying. One, add some weight to the right side since the left side has the battery pack. Maybe that slight weight difference has an impact? Second, the tubes do not bend straight up - I was not super careful when I mounted them. So, I was going to reheat them and straighten them out a little.

Any other suggestions?

Snow rudder?
Maybe a (long) centered rigid tail gliding over/through the snow would keep it straight.

Center the weight,
Center the weight, straighten out the tracks :wink: