Standard vs. Custom Frame

[Cody Carey]

Originally Posted by Viper37

Disingenuous from your point of view, not my own. Save the rhetoric.

The kit bot material is weak. Wack 2 pieces togeather and note the fat chunk of aluminum missing. That is what happens to low quality aluminum stock such as what we are provided with.

On another note, last year bumpers were few and far between, seeing as just about everyone couldnt make it up the ramp with bumpers.

Im not saying this on baseless grounds. Pleanty of people agree with me.

Ok... The Idea of the kitbot frame being weak is something that I had to batter out of my teammates' collective heads when it first came out. The arguments came up of weight, strength, and versatility in designing additional components. Weight was no problem, we just took a 2' length of extruded and a 2' length of kitbot rail and weighed them... even though the kitbot was slightly heavier, the difference was so slight that it didn't matter. Strength was a little harder, and after thinking it over, we decided to test this by smashing samples of both materials in an Arbor press. The Kitbot rail performed exceedingly well. After a little discussion about the ease of adding functional modules to the evenly spaced holes in the kitbot frame, we decided to go for it. We liked the way it held up the first year, and decided to use it again last year.

Last year, we were one of the most physical teams on the field, and the kitbot frame stood up to everything we could throw at it: High speed collisions, 5 robot pile-ups, everything. All with no bumpers and a removed front rail... with the default configuration. The frame is still as structurally sound as the day we shipped it.

The only problem we've had so far, is that the middle axle hole in the frame oblongs and causes drive-chain issues. We only noticed this last year, after two regionals (one of which we won), championships, and an off-season comp.
I believe that signs of wear can and should be expected after the battering we put it through in those four competitions.

And as for This comment:

Originally Posted by Viper37

You must not get very far then.

2 years running we have used the kitbot frame. 2 years running the front and rear are badly smashed in.


Time to get our brand new TIG/CNC Aluminum frame from HP's machine shop!

We won the Philly regional last year.



I did not write this post on baseless grounds, either. I wrote it on two years of experience with the kitbot frame.

[Viper37]

So my reply was deleted...

Ok then.

Ill just retype it.

Im speaking from 2 years of using the basic kit as well.

[=Martin=Taylor=]

Instead of guessing at whether the kit bot is "strong" or "weak" maybe its time we actually did some tests and found out...

These are stress analysis tests my team did with inventor 10. All peices are the same length, and subject to the same variables, so it should give you a pretty acurate comparison.

Kit Bot Side Rail:


10-10 80/20:


Al Tube Stock:


These are all deformation tests. You may be suprised to find that the kit-bot rails are the strongest (which makes sense considering their profile).

I have only the vaguest understanding of how these tests are done. One of our mentors did them.

Despite these tests my team has decided to use 80/20 in our drivetrain b/c it will make chain tensioning easier (we had more problems with chains then frame breaks).

[Madison]

Originally Posted by Viper37

So my reply was deleted...

Ok then.

Ill just retype it.

Im speaking from 2 years of using the basic kit as well.

Your reply consisted of nothing but a smiley face. If contributions aren't relevant to the thread or forum, they'll be deleted.

[Andy Baker]

Originally Posted by Viper37

I never said there was anything wrong with the kit frame, simply that it was weak.

Originally Posted by Viper37

The kit bot material is weak. Wack 2 pieces togeather and note the fat chunk of aluminum missing. That is what happens to low quality aluminum stock such as what we are provided with.

On another note, last year bumpers were few and far between, seeing as just about everyone couldnt make it up the ramp with bumpers.

Im not saying this on baseless grounds. Pleanty of people agree with me.

Weak is a relative term. Whether a person thinks something is weak is their opinion. One thing I have learned in FIRST is that everyone has their own opinions with regard to designing robots.

If someone designs their robot so that 90% of their weight is in the structure of their drive base, then the kitbot chassis is probably not for them. Also, if a team uses their robot as a rolling brick without any regard to scoring the game object, then again the kitbot chassis is again maybe not for them.

The kitbot chassis is not "low quality aluminum stock", if I recall correctly. It is 5052 H32 aluminum.

It may not be for all teams. If a team wants to have some weight left over to have an arm, a lift, a shooter or a latching system and they don't want to spend much time on their drive base, then the kitbot chassis is a perfectly fine structure to use.

Also, many teams got on the ramp while using bumpers. The teams who did not succeed in this either chose the ramp to be a low priority or they did not design their drivebase well.

Andy B.

[ChrisH]

Originally Posted by Andy Baker

Weak is a relative term.

Reminds me of talking about "cool air" - with the Engine (jet) Group. You can roast a turkey in air they think of as cool.

One of the best things you can do for the kitbot is to fill the center bay with a plywood sheet and fasten it to the rails. This will drastically increase the strength of the frame. If you do this and still think the kitbot is "weak" then I suggest you plan on your next robot weighing about 200lbs with a "structurally adequate" frame.

On the other hand I can readily see how somebody who did not do this and just mounted their controls on the cross plate that goes over the kit trannys would regard the frame as weak.

That is because tying the front and back pieces together with a piece of plywood creates what is known as a shear web. Those front and back pieces are effectively turned into an I-beam 36" deep. It will be far stronger than required for FIRST. The key is proper reinforcement in the proper place.

[brennerator]

Also, I'd like to thank everybody for all the great advice they've given us over the last few days. I appreciate it a lot. You guys really have put in a lot of thought into this, and it's been interesting watching this exchange of ideas.

[Gary Dillard]

Originally Posted by Viper37

The kit bot material is weak. Wack 2 pieces togeather and note the fat chunk of aluminum missing. That is what happens to low quality aluminum stock such as what we are provided with.

On another note, last year bumpers were few and far between, seeing as just about everyone couldnt make it up the ramp with bumpers.

Im not saying this on baseless grounds. Pleanty of people agree with me.

??? What competition were YOU involved in? I would say most of the teams we competed with (through 2 regionals and the championship) had bumpers, and I don't recall seeing ANY team that couldn't make it up the ramp because of them. In fact, being traction limited on the diamond plate ramp probably made the bumpers an asset because of the added weight.

Andy already commented on the "low quality aluminum" - 'nuf said.

Time to take a breath and get ready for next season. I recommend you do some detailed research and not make such quick judgments about major components. Most of these decisions are not black and white, they are shades of grey, so making such generalized statements about these are all good or these are all bad is pretty much "baseless".

[Billfred]

Originally Posted by Gary Dillard

Time to take a breath and get ready for next season. I recommend you do some detailed research and not make such quick judgments about major components. Most of these decisions are not black and white, they are shades of grey, so making such generalized statements about these are all good or these are all bad is pretty much "baseless".

You must spread some Reputation around before giving it to Gary Dillard again.

[carbuff]

custom frame is much better but it also has more work that needs to be done:

[Joel J]

Custom frame is better, if you can make a custom frame that's of a higher quality than the kitBot, AND you think its worth the time.

A custom frame may be your only option, if you're doing treads, or something, and value your time.

I don't even think about questions like these.

Are you asking if the KitBot is any good? If so, then yea, its not bad.

[Kellen Hill]

Just a correction but team 1625 has used a custom chassis for both years of its exsistance. Here's the link to the picture our 05 chassis http://www.chiefdelphi.com/media/photos/20834

and there is no good picture of our 06 chassis

I would like to add that custom chassis take a lot longer than kit chassis but our 05 chassis gave us a really really low center of gravity and that helped a lot. This past year it was made to fit what we needed and it worked excellently. Lucky for our team we have an amazing ex-engineer who can aluminum weld very well. Without him we would have probably used the kit chassis. We also have some pretty nice prototype drivetrains that have really nice chassis.

[Dick Linn]

Folks,

The frame is just what holds the all important drivetrain to the rest of the 'bot that does the work. As long as the frame holds it all together and isn't a source of problems, then why worry about it? Our first year robot had a plywood & pine frame. The drive wheels were made from laminated 1 x 4 pine boards with rubber tread glued and stapled on. It did the job, and we had no failures in two competitions.

[Donut]

For those of you looking for good chain tensioning for the kitbot, I finally got pictures up of what we've used the past 2 years.

http://www.chiefdelphi.com/media/photos/26057?
http://www.chiefdelphi.com/media/photos/26058?

With them we've only lost 1 chain the past 2 years (and this was due to another robot hitting our sprocket, bending it at a 90 degree angle, and thus popping the chain off). They are relatively easy to add and can be attached pretty much anyway along the length of the wheel track.

[Dick Linn]

My son made some great chain tensioners out of old skateboard wheels. Cut the groove on a wood lathe at the school shop with a sharp cutoff chisel...