Pneumatic Wheels!

[Massako]

Originally Posted by Kevin Sevcik

Perhaps you could buy just the hubs from andymark? The tires themselves are 200x50 wheel chair tires with matching tubes. There's several options for those on amazon, and a local scooter or mobility store would probably have them as well.

were trying not to purchase anything from andymark and all from Canadian retailers just cause of the exchange rate and shipping costs associated with ordering from the usa

[ebarker]

try Harbor Freight equiv..

http://www.princessauto.com/en/detai...ly/A-p8442410e

[Joe Johnson]

You can optimize whatever Performance Index you want (e.g. buying as little as possible from AM or VP) but I suggest you think hard about what your real goal is because there are really great solutions you are passing up. It is inspiring to have a "we built this" mentality but it is also pretty inspire-sucking (insucking?) to have a chassis that doesn't drive reliably.

Okay. I'm off my soap box. Now let me help.

Before AndyMark came out with those great hubs, Chief Delphi (the team) used to buy so called "Mountain Board" wheels and find ways to get sprockets attached to them (our Stack Attack chassis was bad @ss largely because those wheels -- almost nobody had pneumatic wheels back then).

SO... there was one brand in particular that had a flat disc hub rather than a spoked wheel hub and this lent itself to getting a sprocket attached. They were bright orange* and I think they were on Mongoose brand mountain boards.

Good Googling.

Dr. Joe J.

*which was AWESOME for a CD Robot -- "What's your favorite color, baby?" "ORANGE! AND! BLACK!" (nostalgic tear forms in corner of eye of typist as screen fades to memorirs of stands packed with crazed CD students doing their second favor cheer...)

[cmrnpizzo14]

There are a lot of great Canadian teams out there. Maybe message 610,1241,1114,2056, 4334 (I know there are more of you I just wanted to hit a few of them) and see what they do?

[philso]

You may want to consider the tradeoffs. You will pay more (shipping and exchange rate) for the AndyMark parts. How much will this be compared to what you will be paying to attend one tournament? How much would you save if you use other wheels? How much is your time worth? Does your team have the ability to modify the other wheels in an effective way that will stand up to the rigors of competition? How much weight would you save by using the plastic AndyMark hubs?

Note: we will be trying out some of the AndyMark hubs this evening to see if it can be used to replace the steel hub that comes with the wheel we bought from Harbor Freight.

[Massako]

Originally Posted by philso

You may want to consider the tradeoffs. You will pay more (shipping and exchange rate) for the AndyMark parts. How much will this be compared to what you will be paying to attend one tournament? How much would you save if you use other wheels? How much is your time worth? Does your team have the ability to modify the other wheels in an effective way that will stand up to the rigors of competition? How much weight would you save by using the plastic AndyMark hubs?

Note: we will be trying out some of the AndyMark hubs this evening to see if it can be used to replace the steel hub that comes with the wheel we bought from Harbor Freight.

Yea we are looking at a few that could work pretty well and also just considering purchasing the anymark wheels just for peace of mine knowing that they will work.

[joelg236]

You may also want to consider the delay in getting them from AndyMark now. Not knowing if your drivetrain will work before week 4-5 is a risk not many teams (especially new ones) should take. I would strongly advise trying to find a temporary solution that acts as a PoC in your robot design.

We're up in Calgary, and might have 12 extra wheels on their way to us soon. No guarantees, and certainly don't plan to get them from us, but it's a possibility.

[Massako]

Originally Posted by Joe Johnson

You can optimize whatever Performance Index you want (e.g. buying as little as possible from AM or VP) but I suggest you think hard about what your real goal is because there are really great solutions you are passing up. It is inspiring to have a "we built this" mentality but it is also pretty inspire-sucking (insucking?) to have a chassis that doesn't drive reliably.

Okay. I'm off my soap box. Now let me help.

Before AndyMark came out with those great hubs, Chief Delphi (the team) used to buy so called "Mountain Board" wheels and find ways to get sprockets attached to them (our Stack Attack chassis was bad @ss largely because those wheels -- almost nobody had pneumatic wheels back then).

SO... there was one brand in particular that had a flat disc hub rather than a spoked wheel hub and this lent itself to getting a sprocket attached. They were bright orange* and I think they were on Mongoose brand mountain boards.

Good Googling.

Dr. Joe J.

*which was AWESOME for a CD Robot -- "What's your favorite color, baby?" "ORANGE! AND! BLACK!" (nostalgic tear forms in corner of eye of typist as screen fades to memorirs of stands packed with crazed CD students doing their second favor cheer...)

Awesome thanks we will look into mountain board wheels. we are also thinking about just biting the bullet and going with the andymark wheels as we know this will work for sure. we are using vexpro single reduction clamping gearboxes with a 72:11 gear reduction and just trying to mount a wheel to the 72T gear using a hex hub. Thanks for the Suggestion.

[Kevin Sevcik]

Originally Posted by Massako

Awesome thanks we will look into mountain board wheels. we are also thinking about just biting the bullet and going with the andymark wheels as we know this will work for sure. we are using vexpro single reduction clamping gearboxes with a 72:11 gear reduction and just trying to mount a wheel to the 72T gear using a hex hub. Thanks for the Suggestion.

Wait. Wait, wait, wait. Did I miss something, or are you trying to come straight out of the 11:72 gearbox and into the wheel? Is 11:72 the only reduction you have, or is there another stage of belt reduction in there?

FYI, single CIM into 11:72 into an 8" wheel is something like 24 fps top speed. That's insane and will work horribly for you.

[Massako]

Originally Posted by Kevin Sevcik

Wait. Wait, wait, wait. Did I miss something, or are you trying to come straight out of the 11:72 gearbox and into the wheel? Is 11:72 the only reduction you have, or is there another stage of belt reduction in there?

FYI, single CIM into 11:72 into an 8" wheel is something like 24 fps top speed. That's insane and will work horribly for you.

We are planning to use a 6 cim drive train and we only calculated the speed to be around 18 feet per second and since were using a 6 cim drive train we chose to have as little compromises as possible between speed and strength and we plan to use bag and mini cims for in taking and everything else. if i am completely wrong please let me know as this can all change but this was the design my team decided on so i can bring them up on it. i will also talk to our lead metor and get his opinion on it as his first thoughts when we told him the gear reduction and what we were planning on doing was quite reasonable.

Thanks

[Oblarg]

Originally Posted by Massako

We are planning to use a 6 cim drive train and we only calculated the speed to be around 18 feet per second and since were using a 6 cim drive train we chose to have as little compromises as possible between speed and strength and we plan to use bag and mini cims for in taking and everything else. if i am completely wrong please let me know as this can all change but this was the design my team decided on so i can bring them up on it. i will also talk to our lead metor and get his opinion on it as his first thoughts when we told him the gear reduction and what we were planning on doing was quite reasonable.

Thanks

A 6-CIM drive geared for 18fps (theoretical or actual) is not going to be able to push without running into main breaker trouble, unless your wheels have a very low COF. Something to keep in mind.

It's tempting to think of a 6-CIM drive as a way to gear your drive to move fast and be able to push, but it's not really so simple - in reality, you can easily just end up moving your problems from the 60A breakers to the main breaker.

There can be a "sweet spot" for single-speed 6-CIM drives where you'll be able to push constantly without blowing the main breaker and still move pretty fast (~14 fps with a 110lb robot and AndyMark HiGrip wheels has worked for me in the past), but it depends critically on robot weight, wheel COF, wire lengths, and god knows what else. It doesn't take much to make it go wrong (e.g. compressor turning on at the wrong time), so trying that is "living dangerously" and you should be careful about it. Remember: A blown main breaker is usually a lost match.

So, my advice is this: if you really want to push and move fast, get a two-speed gearbox. 6 CIM drives are great if you want some extra acceleration, but using 6 CIMs alone will not solve that problem for you.

[Massako]

Originally Posted by Oblarg

A 6-CIM drive geared for 18fps (theoretical or actual) is not going to be able to push without running into main breaker trouble, unless your wheels have a very low COF. Something to keep in mind.

It's tempting to think of a 6-CIM drive as a way to gear your drive to move fast and be able to push, but it's not really so simple - in reality, you can easily just end up moving your problems from the 60A breakers to the main breaker.

There can be a "sweet spot" for single-speed 6-CIM drives where you'll be able to push constantly without blowing the main breaker and still move pretty fast (~14 fps with a 110lb robot and AndyMark HiGrip wheels has worked for me in the past), but it depends critically on robot weight, wheel COF, wire lengths, and god knows what else. It doesn't take much to make it go wrong (e.g. compressor turning on at the wrong time), so trying that is "living dangerously" and you should be careful about it. Remember: A blown main breaker is usually a lost match.

So, my advice is this: if you really want to push and move fast, get a two-speed gearbox. 6 CIM drives are great if you want some extra acceleration, but using 6 CIMs alone will not solve that problem for you.

Thanks a lot without this we probably would have done terribly. I'm going to propose we get some clamping gearbox and also ad a 24:72 gear reduction on top of the 11:72 gear reduction lowering the fps to around 10 feet per second.

[Oblarg]

Originally Posted by Massako

Thanks a lot without this we probably would have done terribly. I'm going to propose we get some clamping gearbox and also ad a 24:72 gear reduction on top of the 11:72 gear reduction lowering the fps to around 10 feet per second.

I'd slow both of those down a fair bit.

You're likely never actually going to hit the top speed of an 11:72 gearing on this year's field. Acceleration takes time and space, and the game this year is pretty clearly going to be much more about covering short distances quickly, not long ones.

Moreover, a 10 fps gearing may be safe for constant pushing, but is still potentially problematic pending how grippy your wheels are (if you're using the andymark pneumatic wheels, the answer to this is "very") and how heavy your robot is. ~6-8 FPS should be much safer.

In summary: a top speed of 12-16 FPS and a low speed of 6-8 FPS (theoretical) should serve you a lot better.

[Joe Johnson]

While it is safer to go with higher ratios (slower speeds), and teams will get themselves in trouble a lot faster by having too low of a ratio (i.e. too high of a top speed). It is not risk free to go with a slow robot.

There will be matches where you will need to go end to end to get boulders and weaken the tower over and over.

At 10fps it is going to take what will seem like forever to cycle.

Also, playing defense will require some speed at least. If The Poofs* fake left and then go right, you won't even be in the same county as them when they shoot if you can only go 10fps .

So... ...like almost all things in FIRST, the safest choice is not always the competitive one.

YMMV.

Dr. Joe J.

*to pick a team that is might be fast at random

[Roscoe Plowbots]

Team 3366, Roscoe Plowbots here, we have tried this conversion kit; however, we could not find the order to assemble it. We finally discovered that it requires some self manufacturing. Here is what we did:

Main Hub: hub ground down 3/8'- pulley - wheel, - pulley spacer w/ pulley end cap - hex nut

Right Wheel: small white spacer - large white spacer - inset pulley spacer - pulley - wheel - 34mm custom spacer

Left Wheel: small white spacer - large white spacer - wheel - 34mm custom spacer.

This is for the pneumatic 8' square drive train with 6 wheels. We used a small pvc pipe for the 34 mm custom spacer. Note: on left wheel you do not use the inset pulley spacer, if you do your bolts will get caught on the frame of the robot.