Need some help with forklifts
 

Hello Cd,

I was wondering what material did you use to pull your forklift mast up and down. Last year we used fishing line and that did not work very well. Can you please put a link to your material and we were thinking of using cable? Also could you include pics of your system.

Thanks,

Rc

Re: Need some help with forklifts
 

We didn't use a forklift but our feather was driven by steel cable which might be an option for you. Word of warning if it has plastic coating on it that will peel off LONG before the cable fails so you may want to strip it off in the part you use to secure it down. We were useless an entire match due to striping that plastic off and not being able to raise our elevator which covered our shooter.

Re: Need some help with forklifts
 

We used 3/32" diameter uncoated steel cable for all stages of our lift. We initially worked with 150 lbs. test fishing line, but it stretched far too much to be useful.

Re: Need some help with forklifts
 

228 has used 25 pitch roller chain on our 2007 elevator and Spectra cable on our 2005 elevator.

I'd also like to work on a design that uses timing belts sometime.

Re: Need some help with forklifts
 

Do you have links of where I can buy these products, thanks guys for your help.

Re: Need some help with forklifts
 

Two #25 roller chains for first segment.

Two 1/16" steel cables from ACE Hardware for the carriage segment. We never broke or stretched these cheap cables. They had springs attached to one end that allowed them to stretch when the carriage reached the top.

Can't beat ACE! :D

Picture.

Re: Need some help with forklifts
 

Look through "the usual sources": McMaster-Carr, MSC Direct, Grainger, or Small Parts.

25 pitch roller chain is easy to purchase, although Spectra (sometimes called Dyneema) cable is a bit harder to find. I prefer Spectra cable to steel cable; 7/64" Spectra cord has an ultimate breaking strength of above 1,000 pounds, it doesn't stretch any appreciable amount, and it's a lot lighter than steel cable at only 0.3 lbs per 100 feet. The only real downside is that it costs $1 per foot.

Re: Need some help with forklifts
 

I like spectra for a lot of things because it's so light, flexible, and relatively cheap, but we've discovered that it's pretty annoying for telescoping lifts and such. Spectra has pretty severe creep, which means that it slowly, permanently stretches when it's under load, especially a high load. So any lines that you pretension are inevitably going to get loose as the season progresses. I've since come to appreciate Vectran. It has a lower modulus than spectra, so it will stretch more under load, but it's approximately a heck of a lot more flexible and lighter than steel cable of similar breaking strength, and it has zero creep. Spectra is best purchased from kite shops:
A Wind of Change
Windstar Kites
Vectran lines are available at sailing shops:
Mauri Pro Sailing

EDIT:
Art, you're being taken advantage of if you're paying $1 a foot for spectra if you like it that much. See my links above. Buying in bulk should get you spectra for half that much.

Re: Need some help with forklifts
 

1251 had a lift system this year we used 1/16in thick steel cable and UHMW plastic pulleys with an 1/8th in grove to life our elevator up. The motors were the small and big banebot if my memory serves me corretly and don't quote me on this rs 440 and 550 combined in a custom gearbox. The material for the actual elevator was 2*1 1/8in wall box alumnium. 254/968 has a spool thats really cool its like spring tensioned. I'm sure Cory, Sanddrag or Travis can tell you more about it and where to get them. Some other notes about elevators don't put all the pneumatic lines thru igus on one side if you have more then 4 lines it doesn't work well and run as much line as you can inside then out of the elevator to keep everything out of the way. This will save you alot of dispair and grief during the competiton season.

http://www.chiefdelphi.com/forums/sh...=1251+robot+08

Hope that helps,

-Drew

Re: Need some help with forklifts
 

Where did you get the cable from??? I'll have to ask Cory or if he could explain it here with some pics, that would be greatly appreciated.

Re: Need some help with forklifts
 

Thanks for those links.

I was never the person directly in charge of purchasing spectra cable when we've worked with it, and that's the price I was told. Maybe because we only bought enough for our elevator and a spare, or maybe because we should have shopped around some more. Whatever the case was, I'll be sure to keep my eyes open in the future when 190/228 purchase some.

Re: Need some help with forklifts
 

I'd advise against spectra cable. Yes it is strong, but it doesn't take shock very well at all.

Re: Need some help with forklifts
 

This past year we used 1/8" nylon rope on ours. I was skeptical about how well it would work out, but thankfully it held up and only began to fray recently. In 2005 we used steel cable to drive our parallel arm.

Re: Need some help with forklifts
 

team 675 used #25 chain and # 15 chain to lift our two stage lift

Re: Need some help with forklifts
 

I don't remember the exact name of what we used, but I know it's some sailboat rope. I think like 1/8". We never had any problems with it. It didn't stretch much either. If you have a local West Marine, that's where we bought ours from. I tried finding it on their website, but I didn't find it.

This is probably pretty close: http://www.westmarine.com/webapp/wcs...$@#$@#$@# Num=11452

Our's is blue though, so it may be a different brand. Look at the breaking strength... 530lbs. That's a lot of trackballs.

Re: Need some help with forklifts
 

We used size 25 chain to drive our first stage, with spectra pulling the second up and down.

We used bungee cord to counterbalance the stages the motors didn't have to lift the weight of the them.

One thing to note about using any time of spectra or other line - tieing a knot in it will reduce the strength on the order of 40%. So, for instance, if you had a piece of line with a breaking strength of 500 pounds, and tied a knot in it, the break strength at the point of the knot will only be around 250 pounds. That sounds like a lot, but we managed to break a piece of spectra line with a break strength of over 1000 pounds when we were lifting a trackball and then got hit from the side by another robot (hard). If you can find a local rigger or a West Marine, they can splice the rope for you and eliminate the sharp bends that you'll create by tieing a knot. Or if you can "wrap" the spectra around whatever you're tieing it to several times then tie a couple half hitches, you'll eliminate that problem.

Shock loads are killer. Forces in a 10 mph collision have been measured at over 8 g's in the auto industry. We go a lot faster than that.

Another thing to note is that most spectra will not have a cover on it like your standard "West Marine" line, and that it is very susceptible to chafe. Vectran less so but you will certainly pay through the nose for vectran or any other high-tech line.

Re: Need some help with forklifts
 

222 has used 1/8" steel cable, 3/32" steel cable, 1/8" spectra cable, #25 chain and timing belts for extension devices. Out of everything we used I would say that I liked the chain and timing belt the best. You can't get much simpler. We used steel cable for years and that worked out well for us but many of us got tired of the frays on the steel cable making us bleed. So we eventually moved onto Spectra cable. I will utter the woes of the spectra cable creep. It gets very annoying. #25 chain is bullet proof for most FIRST lifts and can be as simple as a sprocket on a motor and a sprocket on a fixed member and an attachment block to the piece you want to extend. Timing belts can be used the same way the chain can, they are lighter and if tensioned correctly almost as strong. We used the timing belts for extension in our arm this year and we were impressed with how smooth the motion was. As far as chains and timing belts go your can find tons of sources. The timing belt and pulleys we used were supplied in the kit this year and they held up great! As far as a source for cables or other types of rope, here's a source I found that's got a little bit of everything.http://www.us-rope-cable.com/?gclid=...FQWAHgodgjYNWw

Hope this helps

Re: Need some help with forklifts
 

We've used 1/4" nylon rope before. It just happened to fit the groove in those ball-bearing sliding door rollers that are available at Home Depot: http://www.homedepot.com/webapp/wcs/...ctId=100200036

One team used some 1" wide nylon web strap, like you find on tie-down straps. That was nice because it would feed nicely on and off the winch mechanism. Plastic strapping used for shipping might work.

Re: Need some help with forklifts
 

We used it this year and it was good stuff once:

You have a friendly attachment as it can easily be cut by sharp edges
You have learned how to tie a good knot. Knots can reduced the strength rating by as much as 75%. Here is 1 link:
http://www.caves.org/section/vertica.../knotrope.html

You keep it relatively clean. (grease and filings can hinder flexibility and lengevity.
You have a good tensioner system.

These are a lot of provotionals, but once these are set, it works great.

Anecdote:
We bought our original stuff from Small Parts for $100 for 100 feet. We had to re-weld a part on our robot right before ship day and it partially fired one of our strings. It broke at our first regional in Chicago. We bought 300 feet in Chicago for $75. The purchase trasaction and pick was an interesting story in itself.

Re: Need some help with forklifts
 

If you go with cable, make sure you have a good crimper. I don't mean a vise, I mean a cable crimper. 330 used to do lifts a lot (then discovered the joys of a single-joint arm), and when they did, they used cable, powered the lift both ways, and used a crimper used for aircraft cables. I don't think we broke any cable or crimps, though we once bent a lift by powering down while it was all the way down. Yes, bent.

Re: Need some help with forklifts
 

Do you know where to get a really good one? Will this work?

7424K88 - McMaster Carr

Re: Need some help with forklifts
 

I'm not sure. We borrowed ours from a mentor...

But what you have is NOT steel cable crimpers.

You want something more like what McMaster calls "wire rope". The 3633T group of crimps and crimpers, to be more exact.

Re: Need some help with forklifts
 

3633T16, is this it? McMaster Carr

Re: Need some help with forklifts
 

Yeah, that's about it. 330 used 3/32 (with sheath, 1/8), so that's more like a 3633T14.

Re: Need some help with forklifts
 

Thanks EricH, I really needed that.

Re: Need some help with forklifts
 

By the way, the sheath is important. It helps keep the cable well behaved and greatly reduces kinking. If a cable kinks you are better off to get rid of it and build a new one than to try and get it to follow the intended path.

You will however need to strip the sheath around crimps and thimbles. Otherwise the crimps won't work properly

ChrisH

Re: Need some help with forklifts
 

Another thing you can use is seatbelt material. It is woven in such a way that it is very strong and durable. Depending on how you build your lift, you may need to modify it a little to use seatbelt material, because it is wider than a cable.

Re: Need some help with forklifts
 

Here's a typical selection of webbing material: http://www.strapworks.com/webbing_an...brics_s/20.htm

In particular: http://www.strapworks.com/Polyester_s/60.htm

If you can get by with 12-15 feet, just buy 1" cargo tie-down straps or lashing straps. They are about $3. each at Harbor Freight.

Re: Need some help with forklifts
 

We've built 3 different lifts in 4 years. Here's some of the things we've learned from each:

2005
In 2005 we used a cable (3/32" core, 1/8 OD) driven lift. Each side of the lift had a cable, this was to prevent racking and for redundancy. The cables were tensioned with two turn buckles. It was power up, gravity down using an old van door motor. We used no encoders for position sensing.

Pros:
The cable never broke. The turn buckles provided a quick and off the shelf method for cable tensioning.

Cons:
When the motor stalled we would lose the spool of cable and be out for the rest of the match.

2007
In 2007 we used a chain driven lift. A single 25 chain gave us the ability to power up and down. We used a single fisher price motor -> AM Planetary -> BaneBots Planetary to drive the lift. We added an encoder to simplify the control on the lift. We also used 80/20 extruded aluminum and 80/20 slides for the structure of the lift. The motor assembly was on a slide so tensioning the chain was as easy as loosening a couple screws and sliding the motor our.

Pros:
We were power up and power down. The single fisher price motor was plenty of power to move the lift up and down. We were able to go from ground to the top row of the rack in just a couple seconds. The encoder allowed us to maintain our height without a lot of driver finesse.

Cons:
The chain was very heavy, however once it was on we never had to mess with it again. I think we calculated something between 20-25 ft. of chain being used. Between our competition and practice robot we used about 75ft. of 25 chain at $162/ 50ft. spool. Obviously not a cheap solution.

2008
This year we used a 968/254 style lift. The lift was driven by two cables (1/16, no coating) and two fisher price motors running into a custom gearbox. We used to cables for redundancy and to prevent racking. Once again an encoder was used for position sensing. The cables were looped into two eye bolts. By tightening the nut on the eyebolt we could tension the cable.

Pros:
Power up and down, again. Fairly inexpensive to build. Lighter than the 2007 lift. The cables never broke, however we did lose a crimp because someone over tensioned the cables. The encoder allowed us to easily set and maintain positions.

Cons:
In our first competition we had some minor racking problems due to spacing and alignment, which is critical for a lift of this type. By Atlanta we had fixed all of our racking problems.

Overall lessons to be learned:

• Do not power up/gravity down. This can become a major headache at competitions.
• 1/16 steel wire rope is plenty strong enough.
• Tensioning should not be over looked on any lift system. Not mater what you're using it's going to stretch over time and stretching can end up killing your lift if you don't have a tensioner.

Re: Need some help with forklifts
 

We used the RS540 and RS550 motors. Also the cable we used was 1/16" stainless steel.

Our spool was 3" diameter rotating at around 400 RPMs.

Re: Need some help with forklifts
 

Jon Jack, do you have any pics??? Thanks guys for all the help and more ideas and pics would be helpful to team 1323 and a lot of rookie teams. So if you could post some pics of your robot here along with an explanation of how it works, it would be really helpful.

Re: Need some help with forklifts
 

i know this is a lift tread but just on thing i want to bring up is that always consider arm before lift, always. proof of this is beachbot time and time again that simplicity kills all else. are team is finally making the transition and we already prototyped a strong fast arm for 09.

but to answer your question on materials we've been doing elevators every year expect for 06 and we've done custom lift frames to bosch (very expensive if your doing two). we've tried both spectra and steel cable. 1/8in steel cable uncoated works fine but the coated versions were a problem in terms of flexibility. spectra on the other hand is good if you take a lot of care in tensioning the it so it doesn't get cut up in anything. but my choice between the two would be steel cable. we used spectra on our lift this year and went through i believe 200f of the stuff. first spool had a breaking force of over a 100lbs and the other had breaking force of over 1500lbs. it was a bosch elevator forklift pulling up and gravity drop using 2 light senors for bottom and top limits so the spectra wouldn't come off the pulley. but the major problem would be spectra getting caught up every minute in the elevator because the string wouldn't tension at the same time that the elevator would drop. to keep string from getting caught in other areas we ended up using those key chain/card zippy things that act like tape measures pulling in. that had solved the problem most of the time. but if u want proof of elevator failer in action just watch some of our matches at waterloo you'll see the elevator go up and then get stuck either because it came of the pulley or getting caught.

but please please consider arm before elevator one because it'll take much less time to build second because its simple beyond belief and third its proven by 330.

Re: Need some help with forklifts
 

Yes, we have making arms for the last 6 years and we just wanted to test out the forklifts, thatz all. But we will be probably going for an arm. We loved the beachbots robot this year and last. Very nice bot guys. Congrats on winning IRI.

Re: Need some help with forklifts
 

sry bout the rant type thing i didnt realize the situation

Re: Need some help with forklifts
 

don't worry about it, it was a good thing.

Re: Need some help with forklifts
 

kajeevan, what you might not realize is that the BeachBots built lifts on most of their robots between 1999 and 2004, with the exception of 2003's 4-bar linkage. We've proved lifts, too. Go do a search for 330 in CD-Media, and you just might find our 2001 robot and our 2004 robot. The blue structure is a lift.

If we need to, we can do a lift again. It's better for certain applications. For others, it isn't.

Re: Need some help with forklifts
 

never realized i've only seen 330s 05-08 i guess i shouldnt have assumed

Re: Need some help with forklifts
 

There are pictures of all of our robots on our team gallery.

Re: Need some help with forklifts
 

1760 had a very nice lift with #25 chain on the lower stage and 3/32 steel cable on the top. (We get our chain at McMaster-Carr and our cable from Lowes.)

The lower stage had dual chains on sprockets between 2 - 1/2 inch steel rods. (The rods were held in place by brass bushings.) The motor then drove the lower rod through a third sprocket. Power up and down.

The upper stage had a single 3/32 inch cable that was fastened in such a way that the upper stage lifted automagically when the lower stage lifted. Power up (indirectly) and gravity down. We used PVC pipe over an alluminum tube at the top of the lower stage as the pully.

One trick I have not seen mentioned is that we used cable clamps to fasten the cable. (U-shaped bolts with a cast wedge to hold the wire loop together. Also from Lowes). I believe these are much superior to knots. We never had a problem with them.

We did have some issues with the cable jumping the sprockets on one side, but it was managable. We also used zip ties as a floating cable tensioner. (You would think it would bind up or get stuck, but it has worked for us for two years now. )