Input On Steel chassis w/wood inset

[Henry_Mareck]

yes, the kit frame is a very solid start. My statement that we would use it if it got better was misplaced, it is definitley a robust frame.
However, i think that we can put in the extra effort to create a personalized base that meets all the specifications we want it to.
I don't think the kit frame is low enough to the ground for my liking. does anyone know how much the kit frame weighs, anyway?

Edit: if i remember correctly, we were allied with 456 in the finals. Too bad we lost, though. unfortunatley, i do not remember you robot very well

Edit #2 : i need to learn to read, eh?

guess what? another edit! : i should have said we will not use the default kit frame

[Andrew Blair]

I don't know exactly how much it weighs, but it's comparable to an extruded frame of it's size. Under 10 lbs. The idea of the kit frame is that even if you didn't like to default setup, you could modify as you liked. We put blocks inside the rails and constructed our drivetrain from there, much lower to the ground.

[Karthik]

Originally Posted by Henry_Mareck

I don't think the kit frame is low enough to the ground for my liking.

It's all in how you use it. 121 used the kit frame in a "low rider" conifguration with much success.

[greencactus3]

Originally Posted by Karthik

It's all in how you use it. 121 used the kit frame in a "low rider" conifguration with much success.

slightly offtopic but while we're on rideheight, what is the minimum ground clearance most people would attempt. assuming the playing field is a completely flat surface or carpet. and using pretty solid tires not spongy ones or pneumatic ones. ones with very little give.

[Cory]

Originally Posted by greencactus3

slightly offtopic but while we're on rideheight, what is the minimum ground clearance most people would attempt. assuming the playing field is a completely flat surface or carpet. and using pretty solid tires not spongy ones or pneumatic ones. ones with very little give.

I'd say probably at least 3/4 to 1", given that the floor might not be completely level, and you might encounter other unexpected obstacles.

For instance, you could have bottomed out on the HDPE triangles in the loading zones last year, without a bit of clearance.

[evolution]

Still somewhat off-topic, but a quick technical question -- what are the wheels that 121 used made of?

[ChuckDickerson]

Originally Posted by evolution

Still somewhat off-topic, but a quick technical question -- what are the wheels that 121 used made of?

They look like they may be Colson wheels.

[Ellery]

We've used wood bases on all our bots prior to 2002 and they're been pretty durable and very convenient when mounting anything. But I decided to step away from wood if necessary to reduce weight.

As far as Aluminum Welding - We just had a complimentary TIG welding Class organized by Team 340 and it was an experience. It was alot harder than it looks.
Has anyone tried using this DuraFix stuff seen on TV and at trad shows? It's Aluminum brazing. I tried it on some easy butt welds and it seemed to hold up somewhat and can possibly used for small pieces with lower loads but I really had to crank on it to really break the first time weld I made.

This does require some practice with proper material heating and prepping but it may be an alternative if you don't have access to a TIG welder.

Just something to throw out there... It's a lot cheaper $40/lb of brazing rods from Durafix and only $8/ packet at harborfreight for about 8 -10 rods.


Let me know if you've tried this before.
Ellery

[Not2B]

Originally Posted by Ellery

Has anyone tried using this DuraFix stuff seen on TV and at trad shows? It's Aluminum brazing. I tried it on some easy butt welds and it seemed to hold up somewhat and can possibly used for small pieces with lower loads but I really had to crank on it to really break the first time weld I made.

This does require some practice with proper material heating and prepping but it may be an alternative if you don't have access to a TIG welder.

Just something to throw out there... It's a lot cheaper $40/lb of brazing rods from Durafix and only $8/ packet at harborfreight for about 8 -10 rods.


Let me know if you've tried this before.
Ellery

Yeah, I wondered about that stuff. It's not great. I could break all the joint I made with some good impacts and twisting.

HOWEVER...

Real Al brazing (with the correct flux) is easy enough to do with tools you can pick up at Home Depo (or others). The joints I made a few years ago are still together, and that's after I asked the team to try to tear it apart (with no tools.)

But you'll want to practice, practice, practice... I also like to rivit joints as a back up - belt AND suspenders approach.

[gburlison]

Originally Posted by greencactus3

slightly offtopic but while we're on rideheight, what is the minimum ground clearance most people would attempt. assuming the playing field is a completely flat surface or carpet. and using pretty solid tires not spongy ones or pneumatic ones. ones with very little give.

Last year we designed for 1\2" and ended up with 3/8" since the tread compressed more than we expected. Anytime you have to reach high, you need a low center of gravity. On the otherhand, for 'First Frenzy-Raising the Bar' we had more than 6" of ground clearance, but placing the battery below the axle, helped lower the center of gravity.

[John Simons]

I think that you have an excellent idea with useing a steel frame, as long as you select the proper grade. Our team has been using a 4130 chromoly frame for the past few years and it has worked extremely well for us. First of all, it has a much higher modulus of elasticity than aluminum and therefore will deflect less in an impact let's face it that just tends to happen in these games. Secondly, it's fairly lightweight. I know that you thinking this probably can't be true, but it is. One inch square tubing with a 0.049" wall thickness is only about 18% heavier than 1" sq. aluminum tubing with a 0.125" wall thickness and has about 3 times the strength. Third, this will allow you to weld more easily. It can be welded with a standard MIG, although I do recommend TIG. Or if you're in a pinch or have electronics mounted on the frame it can easily be gas welded. If you want a real world example of where this material is used look no further than autoracing. Most roll cages are built out of this strong material and some vehicle frame are built with nothing but.

If you do decide to use this material you will have to do at least two things to ensure the longevity of the frame. Firstly, you have to paint or clear coat it because 4130 is highly susceptible to corrosion. And secondly I would recommend annealing the frame to reduce stresses that may have been introduced during welding.

[sanddrag]

Chromoly is a bit expensive though and not every metal store stocks it.

Aluminum seems to be the material of choice for FRC robot frames. I don't like hearing "we don't have a TIG so we can't have a welded frame" I hear this far too often. What you should be saying is "we want a welded frame so we're going to find ourselves a sponsor or volunteer with a TIG" Don't say "we can't do it so we won't" say "we can't right now but we sure want to so we will find a way" We don't have a TIG welder, heck, we don't have any welder, but for the last two years we have had a beautifully TIG welded frame and we didn't pay a dime to get it done. There are people out there who can help you out, you just have to let them know your situation.

If you try to make a welded aluminum frame happen and you just can't find anyone willing to help you out with the TIGing, then try to design a bolted or riveted together frame. I bet it will work better than you may think.

[lukevanoort]

Also, for any type of tube or sort of tubish frame, you can stiffen it with structural foam. Just spray it in and let it dry, and you have rigidity, however, I have no idea how much it costs/weighs. For other methods, look at the tuner aftermarket for sport compacts. A Civic or Lancer is about as stiff as tissue paper, but with proper chassis braces they can be stiffer than most sports cars. If you're dead set on saying "we have steel" then a steel tube or bar hammered flat at the ends with threaded holes drilled in and bolted to the kit frame can greatly stregnthen your chassis. Mind you, if you want shock factor I'd advise the material on page 3361 of the McMaster catalog, a bit hard to work with, and it can be hazardous sometimes, but it'll definatly get noticed.

[Danny Diaz]

Originally Posted by lukevanoort

Also, for any type of tube or sort of tubish frame, you can stiffen it with structural foam.

Oh yeah, structural foam is the bomb. We also put wooden dowels inside tubes - the REALLY SMALL bit of added weight is nothing compared to the massively increased structural stability; I swear RaPHael (our robot last year) would have had its tube-based arm destroyed many times over if it wasn't for the wooden inserts!

And Henry, unless you know something I don't know (I won't discount it, I didn't go to the drive train meeting), we've always had our aluminum frames TIG welded by Randy Baden - remember "Randy the Welder"?

Also I want to give a shout-out to team 456, it's always a joy to see what you guys come up with every year - so far "Captain Hook" has been my favorite. Can't wait to see you again at Lone Star!

-Danny

[ChuckDickerson]

Originally Posted by texasdiaz

Also I want to give a shout-out to team 456, it's always a joy to see what you guys come up with every year - so far "Captain Hook" has been my favorite. Can't wait to see you again at Lone Star!

-Danny

Hey Danny, a big shout-out back to 418! Unfortunately, we are going to miss you guys and everyone else at Lone Star this year. We let the team vote on what regional they would like to attend and we decided to try somewhere new this year just for fun. We are heading to DENVER! I have a feeling it may be a bit colder than Houston. We will miss everyone at Lone Star but are looking forward to meeting some new faces in Denver. Best of luck to you guys in Houston! Your bot ROCKED last year!

-Chuck