Structural Foam used in 1993 FIRST competition

[InnovationFirst]

Can anyone remember, way back in FIRST 1993, what the structural foam was called that FIRST privided in the kit of parts. The material was white, about 1" thick, and extremely strong.

Bob Mimlitch

[dlavery]

Originally Posted by InnovationFirst

Can anyone remember, way back in FIRST 1993, what the structural foam was called that FIRST privided in the kit of parts. The material was white, about 1" thick, and extremely strong.

Bob Mimlitch

Bob -

It was "Rohacell" structural foam, made by Performance Plastics Corporation.

-dave

[Richard Wallace]

I did not start doing FIRST until 1996. Rohacell was included in the kit that year and again in 1997. The kit quantity in 1997 was one 1" thick sheet, 24" x 49", of Rohacell P170 structural foam. The 1997 KOP listed Richmond Aircraft Products as the supplier.

[sanddrag]

Now if we could only get our hands on some Aerogel we could make robots as large as the whole field and still be under 130 lbs! That stuff weighs virtually nothing! A little crumbly though. Still very very cool.

[Mike Betts]

Originally Posted by InnovationFirst

Can anyone remember, way back in FIRST 1993, what the structural foam was called that FIRST privided in the kit of parts. The material was white, about 1" thick, and extremely strong...

Bob,

I have the technical info included in the 1996 manual. If you want, I can scan it for you...

As I remember, Rohacel had a huge lead time (9+ months) and we were always afraid to commit to a design using it as we could not get more...

However, it was very impressive stuff. we did incorporate it into one robot as a laminate between two sheets of .032 T6 aluminum and the resulting sandwich was strong as Hades...

The problem was that you needed a large, flat press to make the laminate work. This was possible because we had a large (10 sq ft) press at work (fuel cells) but this was not an option for most teams.

Let us know if you have any more questions...

Regards,

Mike

[InnovationFirst]

To all,

Thanks for all the info. I knew someone would remember.

Bob

[Gdeaver]

A lot of the R/C airplane distributors sell small thin sheets for making wings. A couple layers of fiberglass can make a very tough structure. Unlike regular building foam, this foam can withstand moderate vacuum bagging.

[ChrisCook]

I Think its called Lexan, and its not a foam its a poly carbonite we used the clear stuff this year on our robot.

Lexan Poly carbonite

Team 670
team 1458

[Andy Baker]

Originally Posted by ChrisCook

I Think its called Lexan, and its not a foam its a poly carbonite we used the clear stuff this year on our robot.
Lexan Poly carbonite

Team 670
team 1458

No, it is not. These people who posted before you need to be trusted that they are right. They are talking about a foam that was used on FIRST robots in '93. This is an example of how mentors can teach by showing their experience and knowledge.

Polycarbonate is a very durable plastic, which sells under various trade names. LEXAN was the first polycarbonate, as it was invented by Dr. Dan Fox at General Electric in 1953. Since GE's patent protection ran out, there are many brands of polycarbonate for sale now.

Rohacell is a very different material.

Andy B.

[ChrisH]

Originally Posted by Andy Baker

Rohacell is a very different material.

Andy B.

I never knew that FIRST issued Rohacell in the kits, ( before my time) but it is an aerospace material. I've used it at work on and off since the mid 80's. If you get the proper grade and heat treat it properly it can be formed and bent. You can also use it in the autoclave under pressure when making composite sandwich structures.

But the storage conditions and heat treatment are critical to making it work. Do it wrong and it will just crush on you. It is fun stuff to play with.

ChrisH

[Joe Johnson]

This foam WAS a great material but probably not for robots used in FIRST.

It was light and pretty tough but it really didn't like impact loads.

We used it on our arm in 1997. It was the best choice given the legal material selections available that year, but it was a constant source of worry and concern.

I think it totally exploded a round in NJ. I was not there, but the movie is impressive. We were fighting for position over the goal with another robot and then BAM! Catastrophic Failure and a shower of white foam rained down on the field. There is probably some pictures in the ChiefDelphi archive somewhere of that event. It was a spectacular failure.

At least it glued well ;-)

Bottom line: I was glad that it was taken out of the kit.

Joe J.

[ChrisH]

Originally Posted by Joe Johnson

This foam WAS a great material but probably not for robots used in FIRST.

It was light and pretty tough but it really didn't like impact loads.

We used it on our arm in 1997. It was the best choice given the legal material selections available that year, but it was a constant source of worry and concern.

I think it totally exploded a round in NJ. I was not there, but the movie is impressive. We were fighting for position over the goal with another robot and then BAM! Catastrophic Failure and a shower of white foam rained down on the field. There is probably some pictures in the ChiefDelphi archive somewhere of that event. It was a spectacular failure.

At least it glued well ;-)

Bottom line: I was glad that it was taken out of the kit.

Joe J.

Actually rhoacell still is a great material, but you're right it probably doesn't belong on FIRST robots. It takes a bit of knowledge and experience to use composites of any kind properly. The failure you experienced sounds pretty typical of a composite structure. They tend to build up load and store energy with out a lot of deflection, until it is too much, then it all comes out at once, in a variety of directions

There is a reason this composite fabrication engineer built this year's arm out of PVC.

[RogerR]

Originally Posted by Joe Johnson

This foam WAS a great material but probably not for robots used in FIRST.

It was light and pretty tough but it really didn't like impact loads.

We used it on our arm in 1997. It was the best choice given the legal material selections available that year, but it was a constant source of worry and concern.

I think it totally exploded a round in NJ. I was not there, but the movie is impressive. We were fighting for position over the goal with another robot and then BAM! Catastrophic Failure and a shower of white foam rained down on the field. There is probably some pictures in the ChiefDelphi archive somewhere of that event. It was a spectacular failure.

At least it glued well ;-)

Bottom line: I was glad that it was taken out of the kit.

Joe J.

did you use the foam itself as a structural material? or was it the core to a composite shell? and what'd other teams use the stuff for?

[dlavery]

I remember the Rohacell with somewhat mixed emotions. Our very first year (1996) we ended up using the entire available sheet of Rohacell as the major structural component for the entire robot. The base of the robot was a flat piece of plywood, and all the vertical components were cut from simple rectangular sections of Rohacell. We used the material as-is, as we did not have the ability to treat the material to sandwich it with other composites (actually, if I recall, that wouldn't have been legal under the 1996 rules anyway) or bend/form it. It was very easy to cut, pin, and glue together. That made it very nice for a rookie team to work with. But that year we had an special "no corners left square, no edges left straight, and cover everything with gaudy poster paints" philosophy* So the robot, Rohacell included, was not exactly a thing of great beauty. We tried to move on from that experience as quickly as we could.

-dave

* also known as "we are making this up as we go along - please don't confuse us by telling us the way that it really should be done"