Our team is considering the idea of a forklift. We were wondering for those teams that have done forklifts before, pros, cons, and good designs that are fast and effective.
search for team 254 in last years game (2007)
My team used a forklift in 2005. We made it out of 1in x 1in 80/20 Aluminum. We used delrin slides to connect them, and pulleys and wires to lift it. It worked fast but (if you use a wire) you must keep the wire taunt, and you want to power it up and down. I forget where we purchased the materials from. here is a link to our 2005 gallery
Did you machine or buy the delrin sliders? If you bought them, please find out where, since it would be of great benefit to all of us.
We did a forklift last year, also using 80/20 and delrin slides from the 80/20 catalog. It didn’t work too well, it got stuck a lot and we needed a lot of power to go up, and got jammed on the way down (gravity pulled it down)
I’d recommend finding some other rail and bearing block system. We’ve used a great system before, unfortunately we don’t remember the supplier. It worked great in… '05? for moving those tetras.
Out team used a forklift idea last year. We used a threaded rod to move our claw up and down (similar to the way a vice works). We built the frame for the lift from Bosch extruded aluminum. The same type of aluminum given in this year’s KOP.
For sliders, we used Bosch sliders that were able to bolt onto the aluminum. They worked well.
Problems
We had a lot of problems with our design. When raised, our robot was very top heavy and fell over a lot. It also got jammed when raised.
Hope this helps
The problems I see with a forklift idea is:
*Top heavy- any structure this year is gonna be heavy in order to lift the trackball
*There is always the fear of while trying to put the ball over the overpass and an other team runs in to the back of your robot= game over for you
Our team is has thought through pros and cons of the “forklift” idea, I personally don’t like the high probability that the other 5 robots on the field could run in to your robot while your extended over the overpass. Stick to the “K.I.S.S.” principle. Keep It Simple Stupid
We didn’t exactly use a forklift last year but we did use a similar system. Igus’s DryLin system is great for linear motion. We went to Igus’s site and ordered the beefier version of the stuff in the kit. We loved its performance and gave exactly what our designed called for. To actuate our “shuttle” we used a winch mounted low pulling in both directions.
It should be noted that due to geometric constraints of a 40" ball fitting inside a 28" wide frame with 4/6" wheels at (usually) a 24-25" wheel base that the ball will NOT naturally roll past the front set of wheels.
The only way I’ve been able to CAD a ball rolling into a frame with no obstructions is by using 4" unpowered omni wheels on the front of the bot with an open front-end and no bumpers on the front. The inside edge of the omni wheels will slightly graze the ball as it comes in, which means the precision needed to capture a ball in this manner is pretty high. The inside edges of the left & right omnis are 23" apart, using CAD representations of the 1" wide single rail omnis from superdriodrobots.com. I think, though I haven’t tested, that the quality & performance of a bot will suffer if it’s setup in this manner.
This implies that a forklift MUST:
- Extend outside the dimensions of the bot and
- Be a bit more complex than KISS allows or
- Lift from the long side (38" side) of the bot if the lift is always contained within the 28x38 dimensions, which means your bot drives sideways and takes up alot of racing room or is at least semi-holonomic. Niether is exactly “simple”.
Ah, I have found a source for delrin sliders. Here is the link.
Click the links in this order > Fastening Elements > Movable Fastening Elements > Movable Fastenings > T-Slot Slider, T-Slot Roller, Slide Giude
I know that the robot can only be five feet tall - how are you planning to score with a forklift.
I’ve thought about the idea before and I don’t know the best way to get the ball over the hurdle or even to get the ball of the hurdle.
We did a hybrid two-stage forklift/double-jointed arm last year, with the arm mounted on the top of the forklift. Our linear bearings were 24" heavy duty full extension ball bearing drawer slides from a local hardware store. It worked very nicely, and was very low friction. We got the idea from 229/217 in '05 and it worked well for them too (although I believe their slide was for server racks?).
Our team did a forklift last year. It worked very well, though it did have a habit of jamming when going down. We used 80/20 and those wheels that run up the side in order to make it.
In order to counteract the balance issue, we put both motors in the back, using chains to maintain front wheel drive (thus making it extremely easy to control), and also putting the battery in the back.
One thing that was a problem last year was that (at my suggestion 
) we attempted to make the forklift able to fall, allowing teams more room to ride up on our ramps. This destabilized the forklift to a great degree and made us spend the last few days rectifying the mistake. In short: don’t do anything fancy with your forklift.
The same issues all apply to any robot with an arm.
if anything, forklifts are inherently more stable, because the CG is closer to the center of your robot, vs closer to the front, with an arm extended out in front of you.
In 2005, we used three stages of Igus linear bearings (Drylin?), actuated by steel cables (the setup was a lot like the left pic here) and a winch driven by FPs with those big clunky plastic kit gearboxes. The elevator was mounted close to the center of the bot and it worked great. It was a pain to align those little sliding shuttles, but they didn’t require much maintenance during competition. We fell over once, but I think that was at full extension, about 12 feet, with a very heavy grabber, after getting pushed. Look at my icon for details :yikes: