Drive Base Help

[ctt956]

Originally Posted by redfancy

Wheel-wise, we want pneumatic wheels for sure. We have 8-inch wheels from our original bot, but because we want to upgrade from a 6WD to an 8WD (moat), we want to switch to 6-inch wheels for frame perimeter reasons. Our major concern is being able to get over drive obstacles-have any teams run into issues with 6-inch wheels on obstacles?

I've driven a basic robot with six 6" pnuematic wheels over wooden defenses. It was built on an AndyMark frame from 2012. For motors and gearboxes, it had two CIMs and a ToughBox Mini on each side. There were no bumpers, but it had no problem crossing defenses, even the rock wall. However, I don't think that frame would fit eight 8" wheels; there wasn't a lot of free space between the 6", so I think six 8" would be a very tight fit, if they fit at all. I haven't seen the AM chassis this year though, so it might be different.

[carpedav000]

It seems like using this with pneumatic wheels would be very easy:

http://www.team221.com/viewproduct.php?id=130

[redfancy]

Wow, so much help! You guys are great!

[redfancy]

Ok, to answer some questions:

We are planning on taking the new bot to an offseason event, probably Calgames. Our old bot ran a KoP 6WD with 8-inch pneumatics. We had major issues with our gearboxes, which happened to be the exact same 3-CIM ones suggested before. Since the only thing we could do was defense, our gearboxes took a lot of stress and it was enough to fracture and completely shred our aluminum gears. We were advised to just use 2-CIM systems in the future and also decent steel gears.
Also, we didn't secure our gearboxes very well, and that combined with the hole we had in the frame for intake resulted in the bot bowing inwards and twisting the wheels/axles out of alignment. The wheels were actually hitting the metal of the base. This was probably exacerbated by turning scrub, since all wheels were on the same level. So, we took the bot apart multiple times at competition, which was a pain with the KoP base.
We aren't trying to rebuild the same bot though-we're entirely redesigning.

Also, with 6 8-inch wheels, it was a really really tight fit. We had to trim down the bars perpendicular to the wheels so that they wouldn't hit the metal. Also, does the KoP base have pre-drilled holes that would let us drop wheels a good distance?

The AM2494 and 221's chassis seem simple and stable, but would we be able to drop wheels with them?

After reading through, we're leaning towards the VersaChassis. Also, using four Colsons and four pneumatics sounds good. When teams go over obstacles like the cheval and moat, they tend to fly over and then land. Is stress upon landing an issue with the Colsons?

Thanks so much for the help, everyone!

[carpedav000]

Originally Posted by redfancy

Ok, to answer some questions:

We are planning on taking the new bot to an offseason event, probably Calgames. Our old bot ran a KoP 6WD with 8-inch pneumatics. We had major issues with our gearboxes, which happened to be the exact same 3-CIM ones suggested before. Since the only thing we could do was defense, our gearboxes took a lot of stress and it was enough to fracture and completely shred our aluminum gears. We were advised to just use 2-CIM systems in the future and also decent steel gears.
Also, we didn't secure our gearboxes very well, and that combined with the hole we had in the frame for intake resulted in the bot bowing inwards and twisting the wheels/axles out of alignment. The wheels were actually hitting the metal of the base. This was probably exacerbated by turning scrub, since all wheels were on the same level. So, we took the bot apart multiple times at competition, which was a pain with the KoP base.
We aren't trying to rebuild the same bot though-we're entirely redesigning.

Also, with 6 8-inch wheels, it was a really really tight fit. We had to trim down the bars perpendicular to the wheels so that they wouldn't hit the metal. Also, does the KoP base have pre-drilled holes that would let us drop wheels a good distance?

The AM2494 and 221's chassis seem simple and stable, but would we be able to drop wheels with them?

After reading through, we're leaning towards the VersaChassis. Also, using four Colsons and four pneumatics sounds good. When teams go over obstacles like the cheval and moat, they tend to fly over and then land. Is stress upon landing an issue with the Colsons?

Thanks so much for the help, everyone!

The 221 system does not have a center drop, but you can easily remedy that by using smaller wheels for the outside wheels

[troy_dietz]

Originally Posted by carpedav000

The 221 system does not have a center drop, but you can easily remedy that by using smaller wheels for the outside wheels

If you're using pneumatic tires, you can just inflate the center wheels slightly more than the outer wheels, or use a belt sander to take off some of the tread on the outer wheels. (or both) Not only will it create a drop center, you'll have less issues with turning scrub.

[BetaHelix]

Do you have access to a press brake? If so you could build something similar to our drive this year (pictures below). We used 8 8" wheels with 15mm belts and 4 toughbox micros at 12.57:1 (I think). We used 1/2in of drop on the centre wheels. The side plates are .090 5052 aluminium, laser cut, but could be handmade.

[asid61]

Originally Posted by troy_dietz

If you're using pneumatic tires, you can just inflate the center wheels slightly more than the outer wheels, or use a belt sander to take off some of the tread on the outer wheels. (or both) Not only will it create a drop center, you'll have less issues with turning scrub.

Inflation alone does not work, from our experience this year. Sanding down the tires may help but in the end we ran a 3/8" center drop (although 1/4" was working ok). It would be hard to get enough drop without actively doing something to add it.

[messer5740]

I would be careful with using the angled plate of you plan to have an opening in the middle.

[OccamzRazor]

Originally Posted by asid61

Inflation alone does not work, from our experience this year. Sanding down the tires may help but in the end we ran a 3/8" center drop (although 1/4" was working ok). It would be hard to get enough drop without actively doing something to add it.

The 3/8 drop works well with pneumatic wheels, you are right in that inflation barely does anything at all on these specific AM wheels. I saw a team next to us really struggling at Champs to get their robot to turn without brownout issues because they neglected to include the drop. I told them to try wrapping the center wheel with layers of duct tape and that actually fixed their issues aside from the duct tape appearance.

[Billfred]

Originally Posted by redfancy

Ok, to answer some questions:

We are planning on taking the new bot to an offseason event, probably Calgames. Our old bot ran a KoP 6WD with 8-inch pneumatics. We had major issues with our gearboxes, which happened to be the exact same 3-CIM ones suggested before. Since the only thing we could do was defense, our gearboxes took a lot of stress and it was enough to fracture and completely shred our aluminum gears. We were advised to just use 2-CIM systems in the future and also decent steel gears.
Also, we didn't secure our gearboxes very well, and that combined with the hole we had in the frame for intake resulted in the bot bowing inwards and twisting the wheels/axles out of alignment. The wheels were actually hitting the metal of the base. This was probably exacerbated by turning scrub, since all wheels were on the same level. So, we took the bot apart multiple times at competition, which was a pain with the KoP base.
We aren't trying to rebuild the same bot though-we're entirely redesigning.

Also, with 6 8-inch wheels, it was a really really tight fit. We had to trim down the bars perpendicular to the wheels so that they wouldn't hit the metal. Also, does the KoP base have pre-drilled holes that would let us drop wheels a good distance?

The AM2494 and 221's chassis seem simple and stable, but would we be able to drop wheels with them?

After reading through, we're leaning towards the VersaChassis. Also, using four Colsons and four pneumatics sounds good. When teams go over obstacles like the cheval and moat, they tend to fly over and then land. Is stress upon landing an issue with the Colsons?

Thanks so much for the help, everyone!

From working the AndyMark booth at Championship, I can say you were far from alone with aluminum gear issues this year. (I'm betting you busted the smaller ones first.) Aluminum gears are a nice way to get the edge with a flat field and west coast drive, but they do run up against limitations when subjected to the abuses of this game (both the field defenses and the bigger wheels increasing the loads). If you've got the ToughBox Mini from the kit, give it a look; its steel gears will be plenty for the off-season. You can then use those lessons learned to assess how exotic next year's drivetrain needs to be. (I should point out, 4 of the 5 regional wins I've been around for were with the kit frame; 3 of the 4 had the that-year's-kit gearbox and the other ran the AndyMark 3CIM4U upgrade.)

The Team Cockamamie Robot in 3 Days build also ran an open front and saw the same frame bending you describe on a smaller scale before we parked it--it also had a way-too-small bellypan in hindsight and suffered for that. You aren't going crazy there either. Strongly consider a sturdy plywood bellypan on your offseason robot; it will lower your CG a bit and give you some great resistance against twisting and bending.

If you're using the AM14U3 with 8" pneumatic wheels, there are different hole placements and belts you're supposed to use. They sold them as a kit, which would place the axles at the correct place to avoid notching the end bumpers. It would also space the outer plates out further to cut down further on rubbing.

We didn't drive the Team Cockamamie robot on carpet or at high weight (we were waaaaaaay under), but the drop was enough for that. You can also play with air pressures there; a little less pressure in the corner wheels will increase the effective drop.

4901 used a variation on the 221 chassis for its drivetrain this year, except we knew we wanted drop (especially since our corner wheels were pushed inboard). We ended up using 1x3 tubing for the drive rails, which was overkill but suited the purpose of putting our axle holes exactly where we wanted.

Hope some of these data points help!

[messer5740]

I suggest that if you are redesigning a robot in the offseason to complete the same challenges that Stronghold had such as the moat, I would consider using the AM14U3 from andymark with the Upgrade Kit 6WD with 8" Pneumatic Wheels. This will give you suspension and a bit of bounce when going over obstacles. Just note, this drive base CANNOT go over obstacles without in house customization. Our team noticed that at the competition our robot could not cross any defenses other than the rough terrain. We used an angle grinder to cut off about an inch off of the bottom of the front of our chassis and made an angle so that when we would hit an obstacle it would pop our bot up onto the moat, ramparts, rock wall, or rough terrain, which would allow our wheels to get on top of the defense and drive over with ease. We had only gotten stuck in the moat only one match and that was when our path was obstructed with a boulder. I also suggest adding support in the middle of any chassis to ensure the sides do not cave in (just a precaution)
Hope this helps!

[GeeTwo]

Originally Posted by messer5740

We used an angle grinder to cut off about an inch off of the bottom of the front of our chassis and made an angle so that when we would hit an obstacle it would pop our bot up..

Originally Posted by Billfred

The Team Cockamamie Robot in 3 Days build also ran an open front and saw the same frame bending you describe..

AndyMark also sells optional upgrades for the for the AM14U2/3: a wedge plate to solve this issue, and a cross plate to help with an open front/rear. One wedge plate adds close to 3" of length to the chassis length without increasing the wheelbase, but it does help get over the category B and D defenses. I can't vouch for the cross plate.

[OccamzRazor]

Originally Posted by GeeTwo

AndyMark also sells optional upgrades for the for the AM14U2/3: a wedge plate to solve this issue, and a cross plate to help with an open front/rear. One wedge plate adds close to 3" of length to the chassis length without increasing the wheelbase, but it does help get over the category B and D defenses. I can't vouch for the cross plate.

Plus they also make it easy to run the AM churro (http://www.andymark.com/product-p/am-churro.htm) in between the gear boxes to stop the sagging from happening as much. Tap the ends of each rod and shove some 1/4-20 bolts in from the gearbox side. Most of the teams that had these gearbox sagging issues I noticed had nothing in between their gearboxes. Even the weight of 3 CIM motors can cause that sagging and that alone can shred a gearbox from alignment issues.

See the attached photo. Every team should be supporting their gearboxes in some way because it will also stiffen your frame up.

[messer5740]

Originally Posted by GeeTwo

AndyMark also sells optional upgrades for the for the AM14U2/3: a wedge plate to solve this issue, and a cross plate to help with an open front/rear. One wedge plate adds close to 3" of length to the chassis length without increasing the wheelbase, but it does help get over the category B and D defenses. I can't vouch for the cross plate.

They sold wedge plates?!?!?!