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[brennerator]

See below. Combined duplicate posts from separate threads into a single thread.

-Madison

[Joel J]

Don't make the mistake of leaving your cantilevered wheels out in the open. It cost 60 in 2004, and every "too exposed" cantilevered robot at least once in 2006. At the least, make it so that bumpers can be attached to the robot, to sort of "protect" the wheels.

Moderator note: This is relevant to the posts below it and was taken from another thread. I can't change the timestamp.

[Jonathan Norris]

Originally Posted by Joel J.

Don't make the mistake of leaving your cantilevered wheels out in the open. It cost 60 in 2004, and every "too exposed" cantilevered robot at least once in 2006. At the least, make it so that bumpers can be attached to the robot, to sort of "protect" the wheels.

I remember a match against 254 in 2005 at the Sacramento regional where we were playing defense against them and damaged a few of their exposed wheels. Its definitely a design choice when using live axles like that. I would also recommend that you design for the use of bumpers with exposed wheels like that.

[brennerator]

I apologize,
A different team member wrote up the first post.
Thanks for all the help!

I especially liked the idea of inverting the pillowblock bearing.

If theres anything else you see please dont hesitate to critique us! Its a lot better now than after we CNC the thing.

[EricH]

This is a good start, but I have two questions.
1) Isn't it better to wait and see what the GDC throws at us before designing something? Admittedly, this is easy to change now, but nobody knows what's coming.
2) Will the area with no gearboxes be strong enough? I'm not sure that the side rails will stay straight in that configuration.

[Dick Linn]

What are the dimensions of the rectangular tubing? Is it aluminum? We did a chassis awhile back with cantilevered wheels using a 2" x 4" aluminum frame member (a kit part at the time). Can you say "flexible"? Beware. I vastly prefer axles supported on two sides by frame rails. I am somewhat cautious, but in 5 years, we've had ZERO drivetrain failures, and very little maintenance. When you can't afford spare parts, you tend to do it right the first time.

[Lil' Lavery]

I'd be afraid of using hollow wheels, such as the IFI wheels, in an exposed position like that. Something like the AndyMark performance wheels, AndyMark traction wheels, or some variety of colson wheels may be a better option. Regardless of wheel choice, I would also advise having plenty of spares (even if they don't break, if one tread gets worn out etc., due to the ease of switching live axle wheels, spares are often advantageous). If possible, you're going to want some form of exterior protection (typically a bumper), and not just for the safety of your wheels. 254 had trouble last year when teams discovered that if they hit 254 at high speed, they could often "hop" on top of 254's wheels, making it next to impossible for 254 to move effectively. A good example of this can be found in Newton Quarter-final 2-2.

[EricH]

Originally Posted by Lil' Lavery

If possible, you're going to want some form of exterior protection (typically a bumper), and not just for the safety of your wheels. 254 had trouble last year when teams discovered that if they hit 254 at high speed, they could often "hop" on top of 254's wheels, making it next to impossible for 254 to move effectively. A good example of this can be found in Newton Quarter-final 2-2.

968 had the same problem at LA. Their only loss was when a team somehow got on top of their back frame and slowed them down, to say the least. They later added a bumper, IIRC.

[GMAdan]

Even though you may not want to use a bumper/outside rail. I would extremely recommend it. My team uses ifi tract. wheels and without proper protection they are easily bent/broken, last thing you want is a smashed wheel out on the field. Besides that i like the concept. Though adding an outside rail would also provide a place to mount the other end of the axle, thus making it stronger and lessing the need for such big bearing blocks.

[Cory]

I can't speak for the new IFI traction wheels, but if you were to run last year's version outside the frame like that, they'd last maybe 3-4 matches. You definitely want to protect them somehow.

As to snaprings, you can use them to space your sprockets and such. Make sure you leave yourself some wiggle room between the groove and the sprocket, or else the snapring will not properly seat itself. In the past we've just machined nylon/aluminum tube to the proper length and slid it over the shaft.

[Protronie]

Its a good start but... I think you would be happier with a couple more cross frames to help keep things straight. Just my 2 cents worth....

[Viper37]

Originally Posted by EricH

968 had the same problem at LA. Their only loss was when a team somehow got on top of their back frame and slowed them down, to say the least. They later added a bumper, IIRC.

I witnessed this, and it was particularly nasty. Im not claiming to know the workings of their robot, however simply put, if they shortened the width of the chasis by about 2 inches, they would have room to put stock across the axles as a sort of guard.

But after seeing how succesful that chassis was, it is only a small detail.


To address the poster, you have a good chasis on your hands. However have you considered some sort of shifting tranny? If you use them, they can give you a big advantage as far as driving goes.

[EricH]

Originally Posted by Viper37

I witnessed this, and it was particularly nasty. Im not claiming to know the workings of their robot, however simply put, if they shortened the width of the chasis by about 2 inches, they would have room to put stock across the axles as a sort of guard.

Why shorten the width? You can get stock up to at least 10' and cut it to length.

[Viper37]

Originally Posted by EricH

Why shorten the width? You can get stock up to at least 10' and cut it to length.

Like I said, I dont know their robot. Im just assuming it was already at max witdh.

[Lil' Lavery]

Originally Posted by Viper37

I witnessed this, and it was particularly nasty. Im not claiming to know the workings of their robot, however simply put, if they shortened the width of the chasis by about 2 inches, they would have room to put stock across the axles as a sort of guard.

But after seeing how succesful that chassis was, it is only a small detail.

One of the big advantages to having exposed wheels (such as also in the design central to this thread) is the ability to quickly replace your wheels. This is especially true on live axles (as also in this frame design). Reportedly 968 could switch an individual wheel in around 1 minute (or less) with their exposed, cantilevered, live axle design last year. Whether some sort of guard or bumper mount that is quickly and easily removable (or doesn't inhibit replacing wheels) can be added is a challenge left up to the individual team.