View Full Version : Corkscrew drivetrain

10-23-2004, 08:26 PM
I'm looking for information or help on making this type of drivetrain for a small combat robot. I've seen examples of this in a toy that Tyco makes. Any help would be appreciated. Here's a link to the toy.

Hal C.

10-23-2004, 08:52 PM
It looks like the motors are in the pods. One reversable motor for each one for changing direction. I think if I were going to make those corkscrews I'd employ a welder to attach "ribbons" around the cylinders. Steel would be awful heavy and a lot of mass to spin so it looks like aluminum would be in order. Someone really needs to make a cheap tig welder...

10-23-2004, 08:54 PM
Looks like it would only work on carpet or loose soil.
on a shiny hard surface , i could not see it working , unless the edges of the screws were rubber lined or something.
all the best.,mark

10-23-2004, 08:58 PM
There was/is actually a full sized vehicle based on that design,to big 4'diameter pontoons driven by hydrualic motors,made for coning through marshes carrying heavy loads.

10-23-2004, 10:30 PM
It's the end of summer and time to put away the lawn mower (http://www.hugi.is/hahradi/bigboxes.php?box_id=51208&f_id=1159) and fire up the snowmobile (http://www.allroutes.to/modeltandlombard/12/images/MVC-006F.JPG). http://bbs.homeshopmachinist.net//smile.gif

10-24-2004, 12:35 AM
I don't know how big a diameter you'd want to make it, but you could use large flat thin washers to make the helices. Slit them and twist into a helical shape, them stack them onto a suitable form. Line em all up and braze the mating ends together. You could probably just epoxy that to the tube.

10-25-2004, 07:05 PM
I'm hoping to use this in a 6 lb robot. If I interpret the photos correctly the screws have opposite pitch; one left hand and one right hand. These would rotate in opposite directions to go in a forward or backward direction. If you turn the screws in the same direction, I'm assuming the drive train would "juke" to the left or right. Would this be a correct assumption?

Hal C.

10-25-2004, 09:02 PM
there was an episode of Junk Yard Wars last season where they made a vehicle to travel through snow with this type of drive train.

It didn't work.

this drive train involves a TON of slippage, so it is not suitable for anything but loose material such as snow, mud, tanbark or similar.


10-25-2004, 10:00 PM
Turning both impellers in the same direction would probably cause it to slide sideways. It would turn as well if there was some slippage of the blades on the surface it's run on. The tightest turns would be made by stopping one blade completely.
Another thought I had on this is to line the spirals with wheels, a row on each side of the spiral, and staggered. As the screws rotate, the wheels would spin, so on a hard surface, there wouldn't be any 'scrubbing', but there would be forward or backward motion. This is just a mental idea, and maybe not practical, given the large number of tiny wheels, but it would work to reduce friction on a hard surface. There's a complex castor made using this idea.
It looks to me like the concept would best be used for a boat on a swamp, where the screws are the pontoons, and the blades,(one long blade each side actually) would have no ability to clog on anything.
I haven't looked at the picture again, but it also occured to me that there might be more than one 'start' per screw, two helixes, maybe three.
There's going to be a bit of math involved to cover a the radii of the 'blade', b the diameter of the drum, and c the pitch of the blade.
Come to think of it more, I'm coming back around to the washer idea, only now I see that you could have a shop punch out sheet aluminum discs for the outer diameter, and punch the inner hole as well. You can choose the sizes more easily than trying to buy suitable washers. You could laminate two layers therefore not having to make a butt joint between sections.
Assembly is still an issue, I don't know how you would efficiently join the parts together. Maybe a different material that can be glued easily would make more sense. I wonder if the blade could be made in one section from fiberglass-

10-25-2004, 10:30 PM
One of the more complex fabrication jobs I have seen was at our local job shop. The wood chip powered co-generation plant in town need a new chip auger. I saw the finished part in the shop. The core was about 1.5' in diameter forming a cone about 12 feet long to a diameter of about 1 foot. On it was a spiral smoothly varying in diameter to match the core as well as smoothly varying in pitch. Each turn of the spiral had been cut on the CNC plasma cutter as a giant washer, then slit and stretched to make a turn of the spiral. I'm glad I didn't have to do the math.

Paul Alciatore
10-26-2004, 01:06 AM
Why not make the barrels out of galvanized sheet metal and solder copper or brass tubing around them for the spirals.

Paul A.

10-26-2004, 12:30 PM
Whats wrong with wheels?

10-26-2004, 12:41 PM
I saw a picture of a Fordson tractor with an aftermarket drive system like this installed. I believe it was used for operating in heavy snow and mucky conditions. From the pictures it seemed to be a problem to steer on grassy terrain. Lots of torn up grass in the picture.


10-26-2004, 01:20 PM
<font face="Verdana, Arial" size="2">Originally posted by BillH:
Whats wrong with wheels?</font>

Come-on, wheels are OLD technology http://bbs.homeshopmachinist.net//biggrin.gif

With this fightin robot do you get a weight handicap for callin it a walkin bot?

6 lbs. is pretty light. I would keep the metal out and think plastics. I would use a plastic tube (PVC?)for the drums and for the runners I would use rubber. Think about the narrow rubber tires from kids toys (1/4" thick in various diameters) or O rings of 1/4" thickness.

Do like the other guys said and cut in half then "wrap" it around the tube. Secure it with the proper glue for what type of rubber you are using. That should not be a problem due to the advance state of adhesive technology these days.

You could fit DC motors inside the PVC tubes? JRouche

10-26-2004, 07:26 PM
I'm hoping with this type of drive sytem to have the ability to move or "juke" sideways rather than using the more popular skid steering system. Definite advantage for a bot with body spinner weapon system.

Hal C.

www.teampyramid.com (http://www.teampyramid.com)

10-26-2004, 07:58 PM
Wondering though, what kind of weapon could you use against a spinner anyhow? Play bumper cars? and hope that you stop his momentum? THen what?

10-26-2004, 09:15 PM
<font face="Verdana, Arial" size="2">Originally posted by BillH:
Wondering though, what kind of weapon could you use against a spinner anyhow? Play bumper cars? and hope that you stop his momentum? Then what?</font>

Wedges (like what I have built in the past) work well against spinners. If you can get under them then you can push them into the sides or corners of the arena. If they are still spinning at this point you stop them and maybe even use their own momentum to flip them over. Depends on how low the wedge is Vs how close to the floor your spinner is. If you are pushing the spinner around the arena with him unable to control his movement it is points in the wedges favor. It's a matter of who is in control.

Hal C.
www.teampyramid.com (http://www.teampyramid.com)

10-26-2004, 11:51 PM
FWIW another idea altogether. Make a set of tracks which is just o-rings stretched around two pulleys. That's somewhat normal. Then make a second set that mount at 90 deg to the first. This set can be lowered to raise the others off the floor, and drive the bot sideways. Either set can be used to turn the bot, and if one set went out, the other could still drive the thing in the usual way. If they were all touching the floor at the same time, it could spin wildly.

10-27-2004, 10:23 AM
Halac, then its just bumper cars, hoping the arena kills the opponent. I dont know, I like to see physical damage done, parts fly, holes punched.

10-27-2004, 05:53 PM
<font face="Verdana, Arial" size="2">Originally posted by BillH:
Halac, then its just bumper cars, hoping the arena kills the opponent. I don't know, I like to see physical damage done, parts fly, holes punched.</font>

Oh that does happen. Even the little ant weight (1 lb.) can do some serious damage to their opponents. Take a titanium disk 4" diameter and .125 thick, spin it up to about 10-20K RPM, then watch the pieces fly. Thats why I use polycarbonate as armor. It's light yet tough. I've had 7" skill saw blade running at 8k RPM just glance off with just minor scratching.

Now you're probably thinking what can defeat a wedge? A lower wedge. Or something not seen to often yet but they are making an appearance on the circuits are flippers. There's a couple of companies out there that are making miniature pneumatics to fit the "insect" class bots.

It's kinda like the old game; paper, scissors, and rock. Each one has it advantages and disadvantages.

Hal C.
www.teampyramid.com (http://www.teampyramid.com)

10-27-2004, 08:03 PM
An alternate, crazy, half baked idea: Use solid, hard rubber balls for the wheels. They would have to be partially captive in a housing (think giant mouse balls). Drive fwd/reverse with a shaft with abrasive (sandblasted) surface. Drive sideways with a 2nd shaft orientated 90 degress from the first. Somehow allow the non-driven shaft to swing or pivot up when the other is driven.