Current Progress on Challenge #1

[snowblader13]

Here is how mine is going:

I have mine mostly figured out, but I will see if I have to change anything when I try pulling weight again, I changed it around alot since my last try with 4 pounds. I do not think that in my case that it was motor power because the wheels were spinning with no problem, but it was mostly that the bot weighed nothing at the time so it simply couldn't get enough traction. The hardest part that I found is going to be turning in the course.

A little about how it is designed:

Drive Train:
I knew that I had to gear it down alot, so that is where I started with the whole design. After several attempts to get the gearing and position of the motors just right, I took the whole thing apart and reassembled it several times to work out all of the kinks in the design. It uses several worm gears to power the wheels, final gearing is 24:1(A worm gear driving a 24 tooth gear). After an initial test i found out that it would need more weight in the front so I added 2 Power Functions Battery boxes with batteries to give it alot of weight in the front end.

Wheels:
In total as it is it now it uses 12 Of the Motorcycle wheels paired up to make 6 different wheels. Depending on how it ends up working, it does have enough ground clearance so that I could possibly use different wheels if need be. I decided to use the motorcycle wheels based upon Philos tests on all of the wheels, they did the best on short haired carpet. http://philohome.com/traction/traction.htm

Steering:
It used skid steer style steering to be able to power all 6 wheels. I could have used rack and pinion but for the gearing it would have been alot more work to build like this for me, so I went as simple as possible.







Any and all information relative to change on the above information, This is not an official entry.

[Mini_Man176]

Mine isn't going quite so well. It has three wheels at the front being driven by 2 motors with a 27:1 gear ratio. It has 1 wheel at the back for turning but it isn't very stable so I plan to fix that. I also plan to add more drive wheels at the back for grip and power. The NXT brick is pressing down on the wheels. I will also but a PF battery box on top of that to press them down more. It will probably have to be easily removable so that I can see the screen. It can now pull 1.5 kg. I would agree that turning will be the hardest part. My target for this challenge is to pull at least 2.5 kg.

Here's a photo:
http://s3.amazonaws.com/res.homepagenow.com/AHP01NXXXWEK%2Fmedia%2F160167b8dc63e31f75fa0bc94455d7e32c64%2Foriginal.jpg?AWSAccessKeyId=1BR3DPYY2A93MSQYQ2G2&Expires=1208671293&Signature=1yWJxmq0CnZWyGZnxUqDmzy6KbM%3D

EDIT: The other photo link didn't seem to work. I hope this one will!

[NXTMonger]

Mine is definitely not done yet, it can only pull about 2 pounds on a carpet. Interestingly, though, it is geared 1:1 so it goes a bit faster. I had a bit of trouble at first because the only weigh scale we have can only measure about 300 grams. So now I pull a bag of rice that says the net weight is 32 lbs.

[snowblader13]

Well that is part of the challenge. It is not only the amount of weight, but the ratio of weight to time that is the big decider, but you will get more points for the more weight that you pull.

[snowblader13]

well after some more tests being done, i was able to pull about 10 pounds on my carpet in a strait line, wasn't able to get it to turn very good though, i did test it on tile floor and it was alot easier for it to pull. More testing to be done.

[Mini_Man176]

It is interesting that you used 1:1. Could you post a picture?

[NXTMonger]

My new one is 1:8

[NXTMonger]

Sorry, I have no picture. Version 2.0 is dominating both my NXTs now so I had to take 1.0 apart.

[Mini_Man176]

I've now added back drive wheels onto mine, also driven with a 27:1 ger ratio. I used so many gears that I ran out and had to borrow some to get it finished. My sister claims it looks like an aeroplane becuase the bits at the sides (where all the gearing is) are so wide they look like wings. But still this gearing has a problem; the back wheels turn the wrong way!

I've added a PF battery box on the top, but I was thinking of moving it to over the back wheels because there's currently nothing pushing them down. Another problem is turning, not only will the back drive wheels make it hard to turn, I put them where I had put the turning wheel. Now I'm really stuck!

Though I haven't done any tests, when I get the back wheels turning the right way I think it will be able to pull about 4 pounds. Here's a picture:

http://s3.amazonaws.com/res.homepagenow.com/AHP01NXXXWEK%2Fmedia%2F06086ba97a0a4ee607d9cb10f73a72234308%2Foriginal.jpg?AWSAccessKeyId=1BR3DPYY2A93MSQYQ2G2&Expires=1208792327&Signature=BbIq3ibqUFZxgYBIWwW3bsORXDg%3D

[NXTMonger]

unfortunately the link doesn't work

[Mini_Man176]

Why do my photo links never work? I must get another website to host photos.

You can see the photo by going to http://www.miniman176.photos.homepagenow.com/photo_gallery.shtml?txnid=db76aeab89d16fce4239f98cd1176428.
It's the top photo there.

[snowblader13]

We are currently working on a solution to the picture thing.

[Mini_Man176]

Now that I've got the back wheels turning the right way, I was astonished to see that my robot could pull 7 pounds, though it couldn't start with it, I had to let it start first and then put the weight on. It could start with about 6 pounds. Also I've designed a proper sled to put my weights (water bottles) on. I still plan to put the PF battery box on top of the back wheels to press them down more. As for turning, I don't have a clue how that will work. That's for me to figure our later...

Here's a picture:
http://www.miniman176.photos.homepagenow.com/photo_gallery.shtml?cc=0.50308574227694&sort=byuploaddate&limit=9&offset=0&action=details&mediaId=060878691500d6fb96488c520a64c2d0c7a0#albumstart

As for the photo links not working, that's a problem with my site, not yours, and I think I've found a way to get over it.

[snowblader13]

Thats a bummer that it couldn't start with it, you may need to do a little more gearing down with it so it can pull more. Do your wheels slip or does it just not have enough power? Ya turning is going it be tricky. I See you are using legos for your pull sled, i am personally using a cardboard box. but i may have to change if it is easier.'

One other thing to make it turn better, you may want to try to move your sled further back from the robot.

[Mini_Man176]

It's that the wheels slip when it tries to start. I don't think there's much I can do about that at this stage. I am also having some problems with gears slipping even though I think I put them on well.

For the sled, the only thing I have used is LEGO. It seems to slide quite easily under weight and there are plenty of places to tie on string. I might have to try cardboard boxes, they slide easily enough and they could easily hold the weight. With my LEGO sled I find the axles at the back are getting bent. I suppose I did put them on in about 30 seconds.

[NXTMonger]

Just for the record, my creation is all-lego. Even the string is made from linked technic pieces in the form of a makeshift chain. I don't have any pictures yet, but I'll try to get some soon. I think my robot can pull about 6 pounds, possibly more. I still haven't finished the program, though.

[ro1000]

Augh! I haven't even started! I have lots of ideas, though. I'm thinking of gearing my robot down with something near a 1:20 gear ratio...strong enough to pull quite a bit of weight, but still not THAT slow.

[NXTMonger]

Mine's geared 1 to 8 but it can still pull a lot because it has 2 motors per side.

[Mini_Man176]

Yeah, you will be surprised how slow things go with only a small gear ratio.

We should probably email the NXT Step and nxtasy soon to give entrants a full month.

[ro1000]

I built version 1 of mine. It uses two motors geared down with a worm gear to drive two motorcycle wheels, with a linked section in the back with another motor and two more wheels. While it looks really cool, the gearing is too slow and isn't very strong, so I'm gonna make version 2!

[ro1000]

Version 2 is completed! I just finished programming it for my PSPNx, but I won't be able to use that for the competition. I haven't tried any weights yet, but it looks VERY promising! It is a sorta car with, instead of front turning wheels, the middle is linked, to allow turning. The front two wheels are powered indivisually by a motor, and the two back wheels are powered by a motor with a differential gear. Is it okay for me to post it on NXTLog? O ya, ya better email The NXT Step and Nxtasy soon! I think this competition is going to go pretty well!

[ro1000]

My robot can PUSH 12 lbs! I just tried it, and I believe it can do even more! I still have to check with pulling, though.

[Mini_Man176]

Mine was quite bad (only being able to pull 6 lbs at a really slow speed), so I decided to take it apart and start again. I should have enough time to build a new one. It will have worm gears, it will actually be able to turn and I'm aiming for pulling about 10 lbs.

[ro1000]

I still have yet to test my inproved v2 with pulling...Don't know how well it'll work, but I'm hoping to get 10+ lbs...If I can't get at least 10, I'm probably gonna make a third version. V3, I like the sound of that!

[snowblader13]

Has anyone got their robot to go around the whole course yet?

I am going to start programming tomorrow.

If everybody is having problems with turning, i am thinking that we may have to just make a course change!!!

Maybe we will have to make the course go straight for 5 feet instead of having all go strait.

Please tell me your progress, so we can change the rules if need be.