Stronghold Drivetrain Review
 

Hey everybody,

As we wrap up another amazing season for FRC, I'd like for everybody to share their thoughts about how different drivetrains performed in Stronghold.

This year, my team opted for a 6-wheel pneumatic wheeled drivetrain and had great performances from it. We modified the AM14U3 chassis to accommodate the wheels and had no major failures throughout the three competitions we attended.

I'd love to hear about your team's experience whether you used this setup, tank treads, a custom solution, or anything in between. I've seen some really creative and effective drivetrains this year. Is this the year of the Rhino tread, as some proclaimed it to be early in the build season, or the year of the pneumatic tire?

Thanks,
Henry O'C

Re: Stronghold Drivetrain Review
 

Team 5546 (ART) used 10in rubber pneumatic tiller style tires run using geared down simple boxes and 35 chain. As a driver I tried and failed many times in practice to get the bot stuck. We also didn't have the ugly problem with the moat that several six wheel drivetrains had. Also "Hi Mom!!"

Re: Stronghold Drivetrain Review
 

Before Stronghold was released, I really wanted to use something like the WCP bearing blocks for our drivetrain, but our team thought that cantilevered wheels was not a good idea this year.

We ended up going with 8" pneumatic wheels in an 8 wheel drive with 1/4" plate drive pods. No problems with any of it.

I'm wondering what damage teams who used cantilevered wheels sustained, and the thought process they went through in making that choice.

Re: Stronghold Drivetrain Review
 

Our team used the 20 inch nanotube form andymark. We put chain in the rail and connected it to an vex pro 2 cim ball shifter. We attached 8 inch pneumatic wheels to it and riveted a plastic board to the bottom. It worked pretty well except that no a couple of occasions the rivets holding the board on broke and got stuck on defenses. Also we had to replace one of the sprockets in the nanotube because it became stripped from a loose chain.

Re: Stronghold Drivetrain Review
 

We went with the WCD and where had no problems that were caused by the wheels being cantilevered out. We Chose the WCD because it was what we had experience working with. A complete description of our teams drive train is found in the previous post.

Re: Stronghold Drivetrain Review
 

We used 6 7" pneumatic tires on independent double swing-arms with a spring-loaded adjustable suspension. A bit over-engineered? Probably. Cool? yes. Effective? Yes. Probably our most creative drivetrain yet, and something that will be remembered for 236's 2016 robot.

Re: Stronghold Drivetrain Review
 

Straight up WCD 6-wheel 8" pneumatic drivetrain. Center wheel was mounted in one of the Vex plastic bearing blocks, surrounded by two single speed clamping gearboxes. The gearbox axles had gears which drove another gear on the center wheel shaft for two reductions. Outer wheels were mounted on the WCP bearing blocks and driven by 9mm wide belts on 30 tooth Vex pulleys. Don't remember our final gear ratio, it was around for top-speed around 13-14 fps.

I can definitively state that driving 8" wheels with 9mm belts on 30 tooth pulleys works but is pretty marginal. 30 tooth is the biggest you can get and still slide under the CIM on one of the clamping gearboxes, so you're not going to get a lot of torque out of this drivetrain.

We used the metal bearing blocks for the outer wheels because we knew they'd get abuse. The plastic bearing block is the only one a documented C-C distance with the clamping gearbox, so we had to go with it in the middle. It was getting rather wobbly after 2 competitions of play.

Re: Stronghold Drivetrain Review
 

8 WD 8" pneumatic wheels, drop down 1/8. Drive base 32x28. Each wheel powered independently trough a 775 pro and a versa planetary gearbox, 9ft/second.

Even if a motor or a chain stopped working, the robot could still move. The 8 motor drive allowed for some insane pushing power, as well as great traction to get over the outerworks.

Re: Stronghold Drivetrain Review
 

What did you do to prevent burnout? Those little motors seem to be very good at it.

Re: Stronghold Drivetrain Review
 

8-wheel drive with 8" (7.65") dia pneumatic wheels, WCD-configuration using VersaChassis and WCP single speed transmissions (4 CIMs, 14t pinions, and 14:60 2nd stage option) and #35 chain/sprockets.

We played 58 official matches over 4 events (plus around 7-8 practice matches). We played defense in quite a few of those matches, so we put plenty of abuse on the robot. Had a few issues with gearbox damage (sheared gears, loose shafts, exploded bearings) and had to replace quite a few rivets (and a couple gussets) in our chassis over the season. No issues with popped/flat tires, bent axles, or thrown chains. Never got stuck on a defenses all season long.

Re: Stronghold Drivetrain Review
 

6-wheel drive with 8"/7.65" AM pneumatic wheels 9.018" apart. Used #25 chain on 16 tooth sprockets direct C-C +0.018". Powered by a 4 CIM WCP SS gearbox at 15.4 fps. The design originally called for 13t pinions on the CIMs for 17fps instead and no center drop. The frame was basically a square with some cutouts, and was very robustly built excepting the use of 90* sharp gussets instead of triangles on the corners. Fortunately, they held all season. 5/32" rivets everywhere. However:

We experienced problems with the two mounting holes for the CIMs bleeding into each other enough that the 13t distance got way to close to the 12t distance, causing huge lockup of the gearbox until we swapped to 12t pinions. I think I sent an email to WCP about it; making the two different mounting holes actually separate from each other would have been really helpful on their part. We also had to add a 3/8" center drop later in the season. We didn't break any chains, but we did throw one at SVR due to bad assembly of the chain run pre-match (badly misaligned).

Overall, it worked great, except we could beach on the moat. Making the the DT not beach in design is something we can practice in the future. :o

Re: Stronghold Drivetrain Review
 

8 of them. the motors had too much torque to stall, the wheels were just slipping on the carpet before they could get close to burning

Re: Stronghold Drivetrain Review
 

6WD, #25 chain-in-tube, AndyMark 8" pneumatic hubs with tires off Amazon due to supply constraints. We goofed and designed it for an odd number of chain links, which meant half links with all their issues (especially the ones with the little wire instead of the ones you can get off of McMaster). Next time, even number and the acquired-for-Orlando Dark Soul tool will fix this issue...but somehow we never got stranded on the field from chain. Clean living.

The frame was octagonal, so our corner wheels were flipped inboard. Easy to do it either way in the future. We supported the other ends of each axle, which was apparently not necessary (especially with our light weight) but we were being cautious because we knew it was a rough game. This design philosophy will be easy to adapt in future seasons to design needs.

The drive tubes were tied together by a riveted octagonal top pan. This was a mistake, as replacing the chains (which happened a lot early on--remember those half links?) called for faster removal than drilling out and replacing that many rivets. Not having the outboard chassis supports would make it a little easier to service without removing ev-er-y-thing, but a better method is necessary for future years.

We played with softer air pressure in the corner wheels to create more rock and be more compliant on the defenses. Only popped one tube in two regionals, on Friday in Orlando (our second). We drove at least two matches on it before replacing it due to time constraints and never had a problem.

All in all? I give this drivetrain a B. For as many new things as we tried, I'm satisfied.

Re: Stronghold Drivetrain Review
 

This year really helped out with breaking us out of our losing routine of trying to deal with a stock chassis, as I got a 64", 4 road wheel, track system drawn up on CAD.
The only real issues we had with this chassis were tensioning problems.
At our first competition, week 1, the track came off several times throughout the competition, mostly when we pulled a hard turn.

But after fixing that in time for our second, week 6 competition, the chassis worked extremely well, getting a LOT of traction on the carpet, while still retaining it's turning radius.

But if I could change one thing on that drive system, it would be adding active suspension to each road wheel. Making it possible to keep the chassis from bouncing around so much on the defenses, whilst stabilizing the central boulder launcher.

Re: Stronghold Drivetrain Review
 

5940 Used the AMU14 Chassis with the 8 in. Pneumatic wheel upgrade kit. We were lucky to be able to get an upgrade kit before they sold out, and it worked like a dream. Four 6 inch pneu. wheels would probably be better, considering we sheared 4 gears, but the kit was super easy.

Re: Stronghold Drivetrain Review
 

We used 6wd with a setup that mimicked the rocker bogie system on the Mars rovers, and could lock into a normal dropped center 6wd configuration. Vexpro ball shifters and 15mm wide belts, with 36 tooth pulleys, WCD setup with Versablocks.

Once the system was setup correctly and all of the belts tensioned properly, we had zero issues through Vegas and the championship. The drivetrain absorbed shock well and didn't have any issues going over defenses.

If we were to do it all over again, we might just do the standard 6wd pneumatic setup that lots of teams used. It would have saved lots of time during build season.

Re: Stronghold Drivetrain Review
 

We built a full Brecoflex base with the pulleys cantilevered WCD style before the team really inderstood how bad this idea was. We redesigned at the end of week four, with 10wd that looked slightly like the MCC robot, as it used the wcp wheels I had strategically purchased just in case. The four corners were fully independent suspension on coil springs with about 1 1/2" of travel. It ended up being the right choice to redo the bot that late in the season, but our students will not forget the lessons they learned about the design process for next year.

Re: Stronghold Drivetrain Review
 

Your robot was so dope. I enjoyed seeing it in AZ. It was the dopest.

Re: Stronghold Drivetrain Review
 

We decided to use 4 10" pneumatic balloon wheels, thus we needed a custom made frame (out of c-channel), custom belts (not too hard to find) and figure out a way to mount the hubs on them (this took us a whole Saturday because we had it right, then decided it was wrong and redid it, then found that that was wrong and reverted back to the original mount, which has worked perfectly), etc. The wheels helped us literally bounce over the defenses (we did have them slightly overinflated, the max psi they're supposed to have is 2.5 psi, but it's more fun with it bouncing :) ). I have only found one other team that used them, and they used 6 of them.

Re: Stronghold Drivetrain Review
 

I saw your drivetrain at 10k and at the week 0. It looked awesome! Did you guys ever have trouble in pushing matches, with the wheels having no treads?

Re: Stronghold Drivetrain Review
 

We sheared all the teeth off of the 14t gear in the WCP 3-CIM SS. Did some naive load analysis, found that using that gearbox with 8'' wheels is really pushing the strength of the gears. Replaced the 14t gears with steel ones, did not see any more failures.

The WCP gearboxes seem to be designed primarily for 4''/6'' wheels, and using them with larger wheels is marginal. Definitely something to keep in mind for future years.

We originally had 9mm belts, and found that those ratcheted with wheels this big (FRC drive trains usually run them slightly out-of-spec even with 4'' wheels, though the specs given by Gates are for designed lifespans much longer than what anyone expects out of an FRC robot). Swapped to 35 chain, no problems there. WCP cams work like a charm.

Re: Stronghold Drivetrain Review
 

We did a 6WD WCD with 8" Pneumatic tires on custom hubs, Vex Pro 2-CIM ball-shifters, and Vex Pro 15mm belts. The ball-shifters performed flawlessly other than some wear on the 3rd stage pinion gear. I wasn't perfectly happy with the belts. We calculated, designed, and manufactured for perfect center to center distance and they were very loose, and needed significant tensioning. After tensioning, they still ratcheted quite a bit when going from forward to reverse, but we never broke, threw, or wore out one. Also, the robot drove very smooth and quiet with them, which I cannot necessarily say about chains.

We used thunderhex shaft and bearings, which both worked great, except for the thunderhex shaft needing some sanding down. We also made copious use of the Vex molded plastic hex spacers, which are perhaps one of my favorite products they offer entirely.

We used West Coast Products bearing blocks, which really can't be beat for the price. We could easily make ones, but we were not just buying bearing blocks, we were buying time. One thing about these bearing blocks that absolutely drives me nuts is that when used on a 1" wide tube, there is no screw that fits it perfect. The overall width when assembled is something like 1 5/16. As a result, you have to go with 1 3/8 screws, which stick out 1/16. Either the 3/16 thick block should be redesigned to 1/8 or the 1/8 thick block should be redesigned to be 3/16 thick. You just cannot easily get 1 5/16 flat head cap screws. It's an odd design.

Re: Stronghold Drivetrain Review
 

This year was our first year modifying the KOP chassis and we did a combination of the square and long configurations. We also used 8" pneumatics, but only used 6 of them. We barely skated by with a perimeter of 119.5", what dimensions did you guys use? Do you have any pictures of your chassis? I would love to see the wheel spacing.

Re: Stronghold Drivetrain Review
 

6WD with 8" pneumatic wheels. Black. Very cool.
2 3CIM WCP SS gearboxes running the 14/60 gears with 14 tooth pinions 24T sprockets running #35 chain, with an outer plate to hold the shafts in place.

Tensioned chain a couple times and topped off tire pressure. Nothing went wrong besides that, which was real nice. About 10 f/s with good pushing power, could even shove around our 2014 robot ;)

Re: Stronghold Drivetrain Review
 

Team 3072 went with pneumatic tires in the center, with omnis on the corners in a 6wd configuration. We also used Bimba pistons and custom designed plates to give our omni wheels suspension. We can raise and lower the wheels to give us better angles at things, and to help with shooting. We decided that this would give our robot an advantage, considering how high the RW is, not getting stuck in the moat, and helping absorb impact when ramming into things.

Re: Stronghold Drivetrain Review
 

Our unique butterfly module drivetrain really showed it's strength on the rock wall and ramparts compared to other robots in our tier. I really like it but feel like over-engineering our drive train left the rest of the bot really weak and it really showed when we got demolished in the Las Vegas playoffs.

Edit: Here is the max speed it could cross the rock wall: https://www.youtube.com/watch?v=ovvr1kig3ls

I'm a huge fan of 1671's drivetrain this year, that thing is a monster and comparable to 254's.

Re: Stronghold Drivetrain Review
 

6 wheel center drop live axle custom sheet metal chassis (AL 5052 .090") with 10" pneumatic tires from Harbor Freight ($4.99 each). :) We had custom hubs turned by a sponsor. #35 chain with axles placed with specific c-c distance so we didn't need tensioners. AndyMark Cimple Gearbox with 4 Cims geared for a free speed of 8.8 ft/sec.

No issues doing defenses as we could easily go over defenses. No observed damage on the chassis. Even survived a 3 foot fall off of our robot cart at one competition.

We went with 10" pneumatics given our experience in 2012 with the 4" tall center divider. That year we used 8" pneumatics and essentially couldn't get over the center divider or could with extreme difficultly. I am surprised that most 8" wheels had no issues going over the rock wall. I think the ramps had something to do with that which is something we didn't have on the center divider in 2012.

The team initially decided to go with a track drive. Luckily everyone was sold out in the first few days. We have never done a track drive and I wasn't too keen on doing our first one during build season.

Overall, a very good choice for us. Got us our first trip to Champs.

- Tom

Re: Stronghold Drivetrain Review
 

Great thread! Some information on our drivetrain:

-6 wheel tank drivetrain, .25" center drop, 4 CIMs
-10" Harbor Freight pneumatic wheels on laser-cut plywood hubs (for reduced weight, integrated VersaKey pattern and bearing bore)
-32x23" to fit on a single batter segment but accommodate 6 10"wheels and electronics. A cutout at the front provides clearance for the shooter
-Removable panels compactly mount electronic components
-Integrated (but removable) 11:72 single-speed gearboxes with encoder mounts
-4.25" ground clearance, 6" high center of mass
-#35 Chain, 12:36 reduction from gearbox output to middle and front wheels, 30:30 chain between middle and back wheels. CNC-routed HDPE cam chain tensioners are adjusted by tightening screws on the top plate
-Dead axles made from 1/2" Vex tube stock, 1/4" 5052 axle supports laser-cut by sponsor
-Superstructure mounts to 1x1x1/16" square aluminum tubes and can easily be tilted up for access or removed.
-Drivetrain including all electronics except battery weighs ~50 lbs. Wood chassis weighs ~9 lbs

For the second year, the structure was made from 1/4" baltic birch plywood laser-cut in-house on our Trotec Speedy 300 laser. Several refinements were made to our design and manufacturing process, including bolting the plywood to a flat MDF table in the laser to eliminate warping and improve accuracy and using only square nuts pressed flush with one side of the plywood for easier assembly than the centered nuts in last year's robot. The biggest improvement was development of a workflow for production of parts of up to 29x34" on our 29x17" laser cutter by flipping and realigning the plywood. By engraving markers for alignment on the wood, we were able to maintain <~.01" offsets between the two rounds of cutting.

The drivetrain performed essentially flawlessly through the season, allowing quick maneuvering around the field and crossing of all the defenses. No damage was sustained through three events. The only maintenance required was occasional chain tensioner adjustment, chain lubrication and the addition of small aluminum plates to retain improperly installed bearings in the gearboxes.

Some more information can be found in our engineering journal.

Re: Stronghold Drivetrain Review
 

6 pneumatic wheel (AndyMark tires and hubs), drop center, dead axle, #35 chain driven.

Our biggest issue this year is that we went wide instead of long. It made navigating the defenses more difficult than it needed to be. We thought we were being clever by designing our drivetrain so that the wheels would be closer together, but what we didn't factor into our design in our engineer lizardbrains is that we'd be hitting the defenses at high speed. Having some span between the wheels wouldn't have hurt us TOO much and we would have had an easier time of driving quickly. Good thing our driver is pretty flexible :P

https://drive.google.com/open?id=0B4...TgwWEl5ZzlFZ28
Early picture.

EDIT: Definitely used way too many bearings per axle. Next time, not so many.

Re: Stronghold Drivetrain Review
 

We never actually got into any real pushing matches. I think that if we were to get into one, the belts would probably just skip.

On the topic of skipping, we only had major trouble with belts skipping at two points: when the gearboxes were loose, and when some of the c-channel between the frame and the c-channel holding the wheels collapsed in on itself (the second one at the week zero event, which is why we spent about 2-2.5 hours in your shop around lunch instead of competing). We found solutions for both, the first one being to tighten the bolts holding the gearboxes to the frame, and to add a churro shaft holding the gearboxes together so they didn't bounce around so much. The solution for the second one was to bend back the c-channel (using bolts with two nuts on them and tightening them in opposite directions) and to add a 1" piece of o-channel to the middle of the c-channel to prevent bending there.

Another thing we heard from a few people was "You put a boulder in there as a wheel?:ahh: Oh, that's an actual wheel." They did look similar to a boulder, especially when they were new.

Those wheels were very fun to watch on the field. I'm currently putting together a montage of all of our bot's jumps over defenses. Not sure when it will be done, but hopefully before state (no promises though).

Re: Stronghold Drivetrain Review
 

We were the first team to come up with Mecatankanum. It was four mecanum wheels with pulleys on the axles with tank treads attached. This allowed us to fly over all of the drivable obstacles easily. The reason we went with this design was because of the size of the goal compared to the ball as well as we always use mecanums because we love them. The whole robot ended up weighing in at 108 pounds! The guy who came up with the design of the rhino drive design said he loved our design and said it was the coolest drivetrain ever!

Also, we plan on making some improvements like drop down treads and maybe version 2.

Re: Stronghold Drivetrain Review
 

Modified AM14U3 with the gear boxes changed to 12.71:1. We modified the chassis to accept the AM 8 inch pneumatic wheels. The wheels were tapped to take 1/4-20 screws instead of the #10-32 screws it is designed for. We theorize that this will help prevent the shearing of the bolts that secure the drive pulleys to the wheels. We also used 1/8" wall 1x2 tubing to space the frame rails and a single piece of heat formed polycarbonate belly pan that wraps around the entire bottom of the frame to help prevent getting stuck on hard edges.

Re: Stronghold Drivetrain Review
 

We did a 10WD with all 6" Colsons. The center wheel was dropped 1/8" and the outer wheels were raised 1". The center wheel probably should not have been dropped as our wheelbase was too short and we turned too easily. This drivetrain easily handled all of the defenses, except for the moat - sometime between concept and detailed design, the drivetrain got two inches longer, and too much space was left between the drive wheels. This was my only complaint with the drive, other than weight of course.

We did not run into any issues by not using pneumatic wheels, and we enjoyed the greater traction of Colsons. We may have changed the outer wheels to pneumatic if we had to do it again though, just to be safe.

We used 25 chain with 22T sprockets, and it stretched a lot more than it normally did, but we had no issues with throwing chains or damaging sprockets.

Re: Stronghold Drivetrain Review
 

Biggest obstacle for Stronghold drivetrains=bumpers and bumper rules. We went with a custom tank tread system with suspension although it wasn't as advantageous as we hoped the team was happy with its performance.

Re: Stronghold Drivetrain Review
 

Our redesigned chassis held up very well, it consisted of the following:
-8WD with .160 drop centers
-6061 2x1x.125 Tubing except for over wheel rail mounts (1.5x1x.125 Tubing)
-WCP SS 6CIM Gearbox modified for #35 chain, non-direct drive, and spacers to solid aluminum/solid delrin with 1/4-20s
-WCP Bearing blocks with 1/2" Round Bearings
-4140 1/2" steel hex stock turned round through bearings, keyed for sprockets
-6" Pneumatic WCP hubs with diamond tread
-#35 Chain running on 12T sprockets
-Full Wrap Belly Pan

Built it once, only maintenance was checking tire pressure.
It's safe to say that our first time with our modified WCD was a success and the teams new baseline.

Re: Stronghold Drivetrain Review
 

Custom designed Nanotube Modeled off of the Andymark one. 6 9.5" Harbor Freight Wheels. All the wheels were independently driven by a CIM. We never stalled out and we rarely ever got stuck on the moat. It was a rugged and reliable drivetrain and one that we may end using again in the future.

Re: Stronghold Drivetrain Review
 

I'm almost scared to say it but.......swerve:ahh:

We did swerve, because our strategy was not to focus on crossing defences, although the drive train did work well against most in practice. Our strategy was to cycle through the low bar and shoot boulders in the high goal and be quick and efficient with that.

Our drive train had 4 in diameter wheels (custom made), with a 2 speed transmission reaching very fast speeds in high gear. It worked well for our strategy, it helped deter defenders, and in eliminations at Rocket City, helped play defense like no other. We tried to prove that, in objection to popular opinion, swerve would work great for this game, which it did. I can post pictures and designs if there's interest

Re: Stronghold Drivetrain Review
 

We used a West Coast Drive. 6 andymark Pneumatic wheels, 3 stage WCP ball shifter with 4 cims , 1/8 inch drop center with WCP bearing blocks on each end, 35 chain with 12 tooth sprockets. The only problem we ever had was getting stuck on the moat but I think that was a battery issue since it only happened twice during all of our matches.Normally we would just power out if we were hung up. I would have to go back to watch the video to make sure that that was the issue

Re: Stronghold Drivetrain Review
 

We tried to be as COTS as possible this year and it worked great for us. We went with the AndyMark KOP chassis, ran WCP 14:60 single speed gearboxes direct driving the center wheel and used 8" pneumatic tires in a 6WD configuration. #35 chain powered the outer wheels. Our acceleration was fantastic and our top speed was controllable. The drive easily handled every static defense and could push people around as needed. We didn't throw a chain all year and didn't have any chain tensioners.

The only problem we really ran into was maintenance on the drive gearboxes. We killed an 14T aluminum gear at Midwest and spent an hour taking off our drive side and removing the gearbox. It was definitely not designed for maintenance and we are going to take that into account for next year. Usually we wouldn't use 8" wheels in a game though so the bolts used to face mount the gearbox would normally be accessible.

Re: Stronghold Drivetrain Review
 

We used the AM14U3 KoP chassis with 12.7:1 2 CIM gearboxes. For wheels, we ended up getting tires from Princess Auto (Canadian Harbour Freight). We 3d printed a set of 2 piece inner wheels that the inner tube sat on. We then used aluminum plates that sandwiched the tire together after we had problems with breakages on the lamination lines of the 3d printed parts after pressurizing the tires (think of a beadlock tire/wheel). It probably would have been easier to cut down the stems on the steel rims that came with the wheels and then drill a bolt pattern to hold on the hex hubs and pulleys.

Re: Stronghold Drivetrain Review
 

I really want to see someone from 2220 post here-- their drive train was one of a few that I hadn't seen before this year.

As for 2667, we were terribly vanilla. We did pretty much what the OP did, but got wider wheels from Fleet Farm and used some 3D-printed parts to hold the pulleys to the wheels. Surprisingly we had zero failures at our regional and on our practice bot, even though we were using PLA at like 40% fill.

Re: Stronghold Drivetrain Review
 

Can confirm, 558's drivetrain was good this year ::ouch:: :D

Re: Stronghold Drivetrain Review
 

As a rookie team we went with the KOP chassis with 6wd 8" pneumatic wheel upgrade kit. A lot of teams had some crazy complex drivetrains, but I'm really proud of our simple design, which must have been one of the lighter designs. We never got stuck on any defenses, and we could cross at almost full speed with the tires absorbing most of the impact of landing. As a driver, sometimes I wished we had some kind of transmission to have more power for pushing other robots and accelerating quicker, but I can't complain. I always was surprised when I saw teams with tons of experience and complex drivetrains getting hung up on the ramparts or moat.

Re: Stronghold Drivetrain Review
 

100% agree. We modified our AM14U3 to have gear shifting and 8" pneumatic wheels. The gear shifting was totally pointless, but our drive train was able to go over all the terrain defenses, as well as outmanuever any defensive bots that tried to stop us. The one downside we had was that our drivetrain was very wide, making it difficult to line up with the defenses (particularly the freaking sally door).

We got to einstein with that drive train so I would say it has an amazing complexity to effectiveness ratio.

Re: Stronghold Drivetrain Review
 

Yes please do. Im very interested to see how you guys designed you swerve drive to fit this year's game.

Re: Stronghold Drivetrain Review
 

Basic:

• West Coast Drive, 6 tires
• WCP DS - 2 CIM - 14:60 & 24:50 reductions
• Random Amazon tires, 4.15" from middle axle center to floor @ 35 PSI with full robot weight (8.3" diameter wheel for calculations)
• VP Aluminum clamping bearing blocks
• 6WD Drop Center, using the WCP offsets to raise outer/front and lower middle - total drop = 1/8"
• VP Aluminum Hex shaft for wheel axles

Advanced:

• Tire pressures (F/M/R) were 30/35/35
• On the floor, the wheel raise is more like 3/16" due to the tire pressures
• Track Width = 24"
• Wheel Base = 10.5"
• Extra 18T -> 38T sprocket reduction after the gearbox, iirc maximum theoretical speed was 14 ft/s
• Eventually settled on VEX Pro #25 HD chain with VP HD master links (don't use normal master links!), and once we got them everywhere we had no chains come off

Control:

• Standard tank-steering with 2 joysticks
• Optional "Drive Straight" arcade mode, legacy carryover from 2012
• Talon SRX "Speed PID" mapped joystick input to a speed, where maximum joystick input = maximum speed limit set via a constant. Set limit to 9 ft/s early in the season, incrementally raised to 12.5 ft/s by the end of WCMPs.
• Not sure if the kids put in a conversion of ticks/s -> ft/s, or if the SRX has it. Nice feature though.
• Testing showed peak of 12.1 ft/s as read by the SRX's. (Who needs a simulator any more? ;))
• NavX to detect defense crossing - though rough terrain didn't register too well...

Maintenance:

• Check tire pressures 2x a day
• Turns out the middle wheel blocks were 'floating' on one side and therefore would put excess tension on the chain leading to the front wheels. This wasn't a problem once we switched everything to VP HD chain. Probably should have gone #35 in design though.
• There was no metal fatigue on any of the sprockets, but some of the black anodization came off of each sprocket
• Bent one of the rear axles, but since it's WCD it was crazy-easy to replace
• Had a CIM wobble loose at WCMPs. Found it during one of our half-day full robot inspections, so it didn't cause much wear on the gearbox.
• Lightly re-grease gearboxes at start of event and at start of elims

Re: Stronghold Drivetrain Review
 

Team 3026 Orange Crush is proud to present MecaTrak.


MecaTrak is a revolutionary and never before seen dual drive train that gives us the agility of mecanum wheels but by deploying two air cylinders it drops a set of custom made tracks to give us the needed power and traction for defenses and robot to robot challenges. The tracks are made of #35 attachment chain with riveted pads attached to the chain.

We started development in October 2015 and went through several iterations of prototypes before the final product made its way onto the competition bot.

Link to October 2015 Prototype
https://www.youtube.com/watch?v=2JImlM7Ed-Y

Youtube Video of MecaTrak
https://www.youtube.com/watch?v=z2TWEV4n0wQ

MecaTrak Specs

Mecanum

• 6 inch Andy Mark mecanum wheels
• Speed - 15 feet per second

Tracks

• Lifts the robot .5 inches off of the mecanum wheels
• #35 attachment chain with riveted pads
• Pads can hold a box at 25 degrees
• Speed – 8 feet per second

Re: Stronghold Drivetrain Review
 

on 1625 we used tank treads with a twist, we added omni wheels in the front by raising the tread, this allowed us to tighten the turning radius. Only the back pulley and omni made contact while on flat ground although when crossing a defense the tread would contact making it so we had little to no issues crossing. We had originally started with Brecoflex treads although after our first comp we opted to change to our Andymark treads due to wear. The only significant wear we encountered after that was damage to our omnis, they would "jam" and not allow a roller to move after repeated massive impacts. Our whole drivetrain was ran by Vex 775Pros, 2 powered each tank tread (4 total) and 1 for each omni (2 total) Overall we are quite pleased with our choices

Re: Stronghold Drivetrain Review
 

We used Andymark pneumatic tires and didn't have any problems with air pressure. In fact, I'm pretty sure I can count on one hand the number of times we checked them throughout the season. Did you guys have to top yours off frequently?

Re: Stronghold Drivetrain Review
 

We used 8 inch pneumatic wheel in a 6 wheel drive train, using the belts from the Kit of Parts. It worked amazing for breaching the defenses, we never got stuck on anything! Tire pressure was never a problem, we maybe checked it once or twice.

Re: Stronghold Drivetrain Review
 

What did you use for a chassis? Did you use AM wheels? The KoP belts worked very nice for us as well.

Re: Stronghold Drivetrain Review
 

I never thought I'd see the day that we'd use a treaded drive, but this was the year.

Basic:
Waterjetted, folded aluminum drive pods with custom pulley layout
AM Rhino Belts
Rhino pulleys (replaced due to cracking during build season)
Custom single reduction, single speed gearbox ~6:1
2 cims and 1 mini cim per side
static belt tensioner per side

Advanced:
3 pulleys at "ground level" center ~1/8" lower
2 pulleys at "frame level"
Bevel at each end to allow crossing in either direction
~26" Width (outside to outside)
~30" length (outside to outside at frame level pulleys)
~20" of floor contact per side
Belt tension was entirely subjective, but we never threw a belt

Control:
3 Talon SRX motor controllers per side
split stick arcade drive scheme on a game pad

Maintenance:
gearboxes regreased at each competition
pulleys inspected for cracking (none observed through competition season)
belt tension verified
belts never replaced

Observations:
Despite my aversion to treaded drives, I'm very pleased with the behavior and performance of our drive train this season. If the game required it, I think we'd certainly dust this one off and use it again.

Power availability is going to drive our design and gearing decisions in the future. The brown out situation lost us some matches we really should have won, or at a minimum cost us some time because of added difficulty in executing crossings.

If we were approaching this problem again, I firmly believe the choice to neglect to add suspension is the right one. Yes, it would have reduced the wear and tear on the robot from hard impacts, but from observing behavior of other treaded drives that incorporate suspension it would appear that the issue of appropriate spring rates and damping aren't trivial and can lead to really problematic behavior through defense crossings.

Re: Stronghold Drivetrain Review
 

This is what my team used for our drive train. We though it worked really well for breaching and we didn't have to check the tires that much either. Boulders were a problem for my team when we ran over them but I'm not blaming that on the drive train we chose. We also modified it to were it was tank drive which is what our robot last year used so we had more experience driving it like that.

Re: Stronghold Drivetrain Review
 

We went with treads. This is what we did. Over all happy with the results.
http://wiki.team1640.com/index.php?t...II_Drive-Train

Re: Stronghold Drivetrain Review
 

That looks really cool! I know you guys have been developing an amazing swerve drive for the past few years. Were there any thoughts of modifying it to work with 8" pneumatic wheels?

Re: Stronghold Drivetrain Review
 

We went with 6 8" pneumatic wheels and single-speed 3-CIM WC gearboxes. Front and back wheels were mounted in Versablocks, with 1/8" drop centers. Our team has been using 9mm belts for the past couple of years, but we used #35 chain and WCP cam tensioners this year due to space constraints, as we needed much larger belt pulleys than would fit.