pic: REV Robotics building system

[Greg Needel]

[cdm-description=photo]40958[/cdm-description]

[mman1506]

Is the linear motion system supported by ball bearings or bushings?

[Greg Needel]

Is the linear motion system supported by ball bearings or bushings?

The linear motion system uses v-groove ball bearings.


https://photos-6.dropbox.com/t/1/AADnG23nZ7ZWdWm12IlcrEUh1_yAyY6bKSBz570zMPS-Vg/12/68314270/jpeg/1024x768/3/1416016800/0/2/extrusionbearings.jpg/mKqgSLOEXoQbHP-8DXtZQiSLeR2Hy6moji6ylF7anQA

[orangemoore]

Do you have any idea when "very soon" is?

This looks cool.

[mman1506]

The linear motion system uses v-groove ball bearings.


https://lh4.googleusercontent.com/Nhnx5SJlQyufLVL6-sHOD5iUKTFZFoX4Egvr_6BvlA7Bm2ApEqbGwKT295J-_CI6_rF-V6NwOoc=w1373-h807

Awesome! (image seems to be broken BTW)

[cgmv123]

This looks suspiciously similar to a certain Industrial Erector Set.

[tim-tim]

This looks suspiciously similar to a certain Industrial Erector Set.

...but way more suited for the FIRST community.

Greg, any way to get strengths/specs? I am really looking forward to the products REV Robotics are releasing.

[Mike Marandola]

I love the fact that you can use standard hardware with this. I might be missing something obvious, but what are the grooves in the corners meant for.

[Richard Wallace]

I love the fact that you can use standard hardware with this. I might be missing something obvious, but what are the grooves in the corners meant for.
Looks like you could tap them.

[mman1506]

I love the fact that you can use standard hardware with this. I might be missing something obvious, but what are the grooves in the corners meant for.

According to their FB All 5 holes on the end of each profile are designed to be tapped the same thread pitch as the hardware used in the slot. 10-32 for the 1" and M3 for the 15mm profile.

One of the reasons for the extra end tap holes is so your cross members wont have the ability rotate when you use the extrusion as a spanner between 2 plates.

[Mike Marandola]

According to their FB

That makes sense. I was just confuse by the openings. I guess it just makes it easier to manufacture.

[Greg Needel]

This looks suspiciously similar to a certain Industrial Erector Set.

I have used 80/20, Bosch, ITEM, Microrax, and probably a few others over the years and I have loved them and hated them at the same time. They made building and prototyping really easy, but all of them follow the Razer + Blades business model of selling the profile for a reasonable price, but all of the hardware and accessories are expensive. Since you are already in their system you are stuck. This problem is one of the 2 major driving factors in the design of our system.

1) standard hardware decreases the cost of every attachment point from $.40 per nut (.20 if you are lucky) down to .02 by using standard hardware. This gives you the build experience that is so awesome at a much more cost effective price for schools and teams.

2) Linear motion is normally hard or expensive. Over the past 13 seasons I have been involved in FIRST there have been many amazing products which have changed the game (things like the shifting transmission, systems of gearboxes, sprockets, and wheels that just work together). The one thing that has remained hard for teams is linear motion. There are low cost options like drawer slides and more pricey solutions like ground rods and linear bearings but up to this point nothing that was designed with building a robotics elevator in mind. The V groove bearings and integrated features in the 1 inch profile allow for super easy integration anywhere in your mechanism.

I love the fact that you can use standard hardware with this. I might be missing something obvious, but what are the grooves in the corners meant for.

Oh I forgot to mention this on Facebook, but you can also use a NYLOCK nut in our channel for added security.

As for the corners there are a few reasons (some more obvious than others).

When you design a part to be aluminum extruded it is in your best interest to keep a constant wall thickness through your part, this helps with the flow of the aluminum (similar things come into play when designing plastic parts also). Secondly the amount of closed profiles in your extrusion makes the dies more expensive and harder to get consistent results. Specifically speaking to the 15 mm profile it would have been almost impossible to do a closed hole in the corner.

As mentioned above all 5 of the holes can be tapped with allows for some interesting applications, one of which is mounting a hub to the end and driving it with a motor to turn our extrusions into a shaft that could be used for a pickup. Along that same lines the slot in the corner is specifically sized to accept a 1/6" piece of flat stock (lexan or other), I am sure you can probably think of a few times this would be useful :D

[BJC]

snip/

2) Linear motion is normally hard or expensive. Over the past 13 seasons I have been involved in FIRST there have been many amazing products which have changed the game (things like the shifting transmission, systems of gearboxes, sprockets, and wheels that just work together). The one thing that has remained hard for teams is linear motion. There are low cost options like drawer slides and more pricey solutions like ground rods and linear bearings but up to this point nothing that was designed with building a robotics elevator in mind. The V groove bearings and integrated features in the 1 inch profile allow for super easy integration anywhere in your mechanism.

/snip


It seems to me that the x shape and the very thin material that allow for the nut pockets on all four sides make this extrusion very susceptible to twisting loads. I noticed above you advocated using this for an elevator. Currently, many teams prefer 2x1 rectangular tubing for an FRC-type elevator because (among other reasons) its resistance to twisting is highly desirable to prevent binding. While it is probably serviceable in shorter/low loading situations, in a game such as 2011 Logomotion where elevators where the full 60" tall I don't think this extrusion would function very well in place of 2x1.

I do think that this is a really cool addition to teams' resources though. With the sliding nuts on each side it could especially have FRC applications in rapid prototyping.

Cheers, Bryan

[sanddrag]

Generally, with this type of profile available from other manufacturers, the purpose of the T-nut is to drop it in anywhere on the profile, and then it rotates into place before tightening. This allows for easy additions of brackets to the middle section of the beam, even if the end sections already have brackets and hardware installed.

How would this be accomplished with normal hexagonal nuts? Would you pre-load the profile with any and all hex nuts you ever intend on using, and let them float free until you do? Or would you need to disassemble bracketry on one end to add something more to the middle?

[JB987]

Generally, with this type of profile available from other manufacturers, the purpose of the T-nut is to drop it in anywhere on the profile, and then it rotates into place before tightening. This allows for easy additions of brackets to the middle section of the beam, even if the end sections already have brackets and hardware installed.

How would this be accomplished with normal hexagonal nuts? Would you pre-load the profile with any and all hex nuts you ever intend on using, and let them float free until you do? Or would you need to disassemble bracketry on one end to add something more to the middle?

Or perhaps an actual drop in t-nut would also work on this extrusion?

[Greg Needel]

It seems to me that the x shape and the very thin material that allow for the nut pockets on all four sides make this extrusion very susceptible to twisting loads. I noticed above you advocated using this for an elevator. Currently, many teams prefer 2x1 rectangular tubing for an FRC-type elevator because (among other reasons) its resistance to twisting is highly desirable to prevent binding. While it is probably serviceable in shorter/low loading situations, in a game such as 2011 Logomotion where elevators where the full 60" tall I don't think this extrusion would function very well in place of 2x1.

I do think that this is a really cool addition to teams' resources though. With the sliding nuts on each side it could especially have FRC applications in rapid prototyping.

Cheers, Bryan

The profile is actually much stiffer in torsion than what you would expect, but yes a 2x1 would be be stronger. You nailed it, as the implementation of the system is game specific, as some time a bit of twisting is acceptable (light game objects such as 2011). If people wanted to use this with heavier or more stout assemblies you can do a braced 2 post lift style (which I think is actually more common) and where the twisting on the individual member is less of a factor.

I agree about the prototyping, there have been many years when even if our extrusions don't end up on the robot the flexibility to prototype with them is huge.


How would this be accomplished with normal hexagonal nuts? Would you pre-load the profile with any and all hex nuts you ever intend on using, and let them float free until you do? Or would you need to disassemble bracketry on one end to add something more to the middle?


Generally speaking you would load the rails from either side with nuts, but another method I have tested is to cut a clearance hole (just over 3/8) in the channel where you just remove just the retaining flange and then you can drop them in. This almost has no strength loss (bending) and is easy to do with a cordless drill.

Or perhaps an actual drop in t-nut would also work on this extrusion?

I have tested a bunch of t-nuts with the system and some work and some don't. Most 1" profiles use 1/4-20 hardware, where this system uses 10-32 (or 24) so the nuts are bigger than the channel due to the corner holes in the profile. There are some smaller t-nuts designed for smaller profiles that do work with the system. We are not planning on selling t-nuts but if teams find ones that work we will be sure to link them from our product pages so a team can use them if they want that feature. In the future if people really want a drop in t-nut we can investigate making one specifically for this profile.


I love all of these questions! Right now REV is just a small start-up who wants to bring value products to the community. We will always be open to feedback from you all to help make our products better.

[aldaeron]

I know details are coming "very soon" but would you be willing to share the material, MOI, weight per foot and (approx) cost per foot of the two extrusion profiles now? I am sure there are lots of fancy add on plates and connectors that we will see soon on AM.

Thanks!

-matto-

[Chris_Elston]

Very happy to see something for FRC in linear rail. We've used some openbuild rails before with a V-Groove channel. Great stuff to work with. Easy to use. AFFORDABLE and not like 80/20 or Item, especially the PRICE. We live 20 miles from 80/20 and it still cost us alot of money to purchase 80/20 direct from them. We had over $1000 in 80/20 for our pit organizer "general store" we call it. Most of the time we try to have Neff Engineering donate what we need.

But for parts on the robot a v-slot linear rail like this is awesome to see, especially if it will be tailored toward FRC. Here is a sample of openbuild v-slot we've been toying with.

https://www.youtube.com/watch?v=584Z47gTBRY&list=UUw80fFdoAlQzERoYxWPeI1w

[JB987]

Very happy to see something for FRC in linear rail. We've used some openbuild rails before with a V-Groove channel. Great stuff to work with. Easy to use. AFFORDABLE and not like 80/20 or Item, especially the PRICE. We live 20 miles from 80/20 and it still cost us alot of money to purchase 80/20 direct from them. We had over $1000 in 80/20 for our pit organizer "general store" we call it. Most of the time we try to have Neff Engineering donate what we need.

But for parts on the robot a v-slot linear rail like this is awesome to see, especially if it will be tailored toward FRC. Here is a sample of openbuild v-slot we've been toying with.

https://www.youtube.com/watch?v=584Z47gTBRY&list=UUw80fFdoAlQzERoYxWPeI1w

Fantastic product with tons of great potential. Any idea of the per foot cost for rails and cost of some of the roller components? I wonder if they would offer any discount to FIRST teams.

[Monochron]

Our team has recently looked into OpenBeam (http://www.openbeamusa.com/) after having it recommended to us by a nearby team. OB also claims to be interfacable with common hardware and not specialized stuff, though it doesn't seem the have a good V channel like some others. Can't quite tell whether your offering is better just yet, though the fact that you are advertising it on CD is certainly a good sign. :D

[Tristan Lall]

Will you have datasheets with more detailed information like:

Fully dimensioned drawing of the profiles;
List of available lengths;
Tolerance information (whether complete as if for manufacturing, or limited to that which would be useful for interfacing), including some measure of twist per distance;
Standard structural constants (like section moduli) for quick comparison with other systems;
Alloy specifications including composition and temper;
Finish specifications including surface treatment (composition, thickness, hardness) and bulk material properties (hardness, roughness);
Recommended tooling; and
Warranty?

[Greg Needel]

Very happy to see something for FRC in linear rail. We've used some openbuild rails before with a V-Groove channel. Great stuff to work with. Easy to use. AFFORDABLE and not like 80/20 or Item, especially the PRICE. We live 20 miles from 80/20 and it still cost us alot of money to purchase 80/20 direct from them. We had over $1000 in 80/20 for our pit organizer "general store" we call it. Most of the time we try to have Neff Engineering donate what we need.

But for parts on the robot a v-slot linear rail like this is awesome to see, especially if it will be tailored toward FRC. Here is a sample of openbuild v-slot we've been toying with.

https://www.youtube.com/watch?v=584Z47gTBRY&list=UUw80fFdoAlQzERoYxWPeI1w


Our team has recently looked into OpenBeam (http://www.openbeamusa.com/) after having it recommended to us by a nearby team. OB also claims to be interfacable with common hardware and not specialized stuff, though it doesn't seem the have a good V channel like some others. Can't quite tell whether your offering is better just yet, though the fact that you are advertising it on CD is certainly a good sign. :D


I love some of the innovations that some other companies have been coming out with. Things like Open Beam, Maker Beam, Maker Slide, 80/20, ITEM, V-slot, etc. When we were designing these profiles we had to think carefully to optimize what FRC and FTC teams would want in their ideal profile. In keeping with this all of our designs will also be opened sourced so people can build on them and make new advances for their own specific applications.


Will you have datasheets with more detailed information like:

Fully dimensioned drawing of the profiles;
List of available lengths;
Tolerance information (whether complete as if for manufacturing, or limited to that which would be useful for interfacing), including some measure of twist per distance;
Standard structural constants (like section moduli) for quick comparison with other systems;
Alloy specifications including composition and temper;
Finish specifications including surface treatment (composition, thickness, hardness) and bulk material properties (hardness, roughness);
Recommended tooling; and
Warranty?


Yes, we will be releasing most of the information you requested. Here is some basic info now.

Both profiles are 6063-T5 clear Type II anodized. With 2 mm flatness and 3/4 a degree twist tolerances per meter of length.

The Extrusions will be sold in single length options (to reduce shipping costs)

6ft lengths of the 1inch
1 meter lengths of the 15mm

[Richard Wallace]

The Extrusions will be sold in single length options (to reduce shipping costs)

6ft lengths of the 1inch
1 meter lengths of the 15mmIf your choice of lengths is not final now, may I recommend a shorter length for the 1"?

72" (6ft) of this extrusion is too long for most uses on a FIRST (FRC or FTC) robot, and makes for awkward scrap. One meter would be more generally useful, IMO, and would allow you to standardize on packaging for both of your sizes.

[MrRiedemanJACC]

Do you have a Solidworks profile of the extrusion yet? :) Would love to have students start throwing into there and "playing" with it!

[ttldomination]

This is super intriguing. Even some of the other posts in this thread are pretty informative; I didn't know 80-20-esque solutions existed that were linear motion friendly.

I would be interested to see...

1) The final specs relative to 8020
2) The final price
3) How well this interfaces with the existing 8020 solutions.

I think (3) is of particular note. While this solution seems to "free" teams of some of the restraints of 8020, the same teams have often invested significant capital into 8020.

If your choice of lengths is not final now, may I recommend a shorter length for the 1"?

72" (6ft) of this extrusion is too long for most uses on a FIRST (FRC or FTC) robot, and makes for awkward scrap. One meter would be more generally useful, IMO, and would allow you to standardize on packaging for both of your sizes.

I believe the idea is to cut the larger pieces down to size. In the past, my teams have purchased 8020 in 10' lengths simply because it's a bulk purchase. Additionally, if the longest rails are ~3', then teams would probably look over this solution if the game involves reaching particularly high (don't get to maximize the presumed 60" height limit).

- Sunny G.

[Richard Wallace]

... While this solution seems to "free" teams of some of the restraints of 8020, the same teams have often invested significant capital into 8020.
...

I believe the idea is to cut the larger pieces down to size. In the past, my teams have purchased 8020 in 10' lengths simply because it's a bulk purchase. Additionally, if the longest rails are ~3', then teams would probably look over this solution if the game involves reaching particularly high (don't get to maximize the presumed 60" height limit).

- Sunny G.I think this material is more likely to be helpful for teams that do not already have significant capital into 8020.

And of course I understand the idea is to cut larger pieces down to size. I have been doing FRC (and engineering) for more than a few years!:) However, I do believe that 72" would be an awkward [read: potentially wasteful] bulk length if that is the only option, for a 1" extrusion.

[ttldomination]

And of course I understand the idea is to cut larger pieces down to size. I have been doing FRC (and engineering) for more than a few years!:) However, I do believe that 72" would be an awkward [read: potentially wasteful] bulk length if that is the only option, for a 1" extrusion.

Yeah, I've seen you around these parts for a while, which is why I was wondering where this specific concern is coming from.

I'm curious, what's your logic behind 72" being potentially wasteful?

- Sunny G.

[Greg Needel]

I think this material is more likely to be helpful for teams that do not already have significant capital into 8020.

And of course I understand the idea is to cut larger pieces down to size. I have been doing FRC (and engineering) for more than a few years!:) However, I do believe that 72" would be an awkward [read: potentially wasteful] bulk length if that is the only option, for a 1" extrusion.

The 72" length is already set. We chose it for 2 reasons 1) shipping costs for anything over 6ft are extremely high. 2) when teams build elevators, maximizing height is defiantly a factor, so we wanted the longest we could without making teams waste a bunch of money on shipping.

In the future we may offer shorter lengths, but right now we don't have the infrastructure to offer more than 1 length of material. Hopefully we will get feedback from teams who use it (or want to use it) this year and we will look at this for the future.


This is super intriguing. Even some of the other posts in this thread are pretty informative; I didn't know 80-20-esque solutions existed that were linear motion friendly.

I would be interested to see...

1) The final specs relative to 8020
2) The final price
3) How well this interfaces with the existing 8020 solutions.

I think (3) is of particular note. While this solution seems to "free" teams of some of the restraints of 8020, the same teams have often invested significant capital into 8020.

- Sunny G.

This will directly interface with 80/20. All of your existing brackets and gussets will work. The only thing you might need is a washer, as most of the 80/20 profiles are designed for 1/4-20 hardware and we use just slightly smaller 10-32 hardware.

[asid61]

This is great! 10-32 taps and the compatibility with 10-32 nuts should be great for many teams.

[SiliconKnight]

VERY Cool. (Have to dust off my old Chief Delphi account to comment on this)

I'm a former FIRST mentor (Team #824, Students Working Against Time), and the creator of OpenBeam. In the spirit of gracious professionalism, I wish you much luck in your endeavor. :-D

Feel free to get in touch via our contact form on OpenBeamUSA.com. We're always looking for compatible brackets to our ecosystem.

-=- Terence

[ttldomination]

I saw the extrusions are available on AM, and most of it looks decent.

I was wondering, in the images and documents that show the V-Bearing in use, the bearings are attached to a base plate of some sort. Are there plans to provide that base plate + V-Bearings as a kit?

- Sunny G.

[Greg Needel]

I saw the extrusions are available on AM, and most of it looks decent.

I was wondering, in the images and documents that show the V-Bearing in use, the bearings are attached to a base plate of some sort. Are there plans to provide that base plate + V-Bearings as a kit?

- Sunny G.


Yes, There will be a kit. The kit would include 2 bearings, the eccentric + concentric bushings, the mounting plate, and the 2 nuts/bolts you need.

The plates are in transit now from the machine shop, and will be available before kickoff. A late change was made to allow teams to use normal 3/8 bearings with the same plates and bushings to build a 254 style lift using regular 1x2 tubing as another option.

We are going to be posting a whole bunch of applications to www.revrobotics.com over the next couple days.

[ttldomination]

Sweet, looking forward to it.
- Sunny G.

[Greg Needel]

Now that we know what the game is, I thought I would highlight the linear motion capabilities of the REV extrusion.

We have posted some new guides to our website on using the building system, and plan on releasing some full plans for some basic elevators (not complete plans) in the next day or so.


Check out our guides here. http://www.revrobotics.com/building-system-overview/


All of the parts that are out of stock right now for the system, will be in stock early next week.

[Greg Needel]

REV extrusion is now in stock at AndyMark. http://www.andymark.com/product-p/am-2901.htm

all the other parts will be coming back in stock over the next few days.

[aldaeron]

all the other parts will be coming back in stock over the next few days.

The bearings show an ETA of 1/30 - is that still correct?

[Greg Needel]

The bearings show an ETA of 1/30 - is that still correct?

I think that is about right on the bearings, we shipped all of our inventory to AM last week, but it was sold out in less than an hour. We are waiting on fulfillment from our supplier.


In the meanwhile the bearing is a standard size (RM2ZZ) and there are lots of places you can get them now (if you don't mind paying a bit more for them)

VBX sells the most comparable to quality version http://www.vxb.com/page/bearings/PROD/V-Groove-Bearings/Kit8407

There are some lower cost options out there that are the right size, but I have not tested them to know the quality. Quality significantly varies bearing to bearing, so be warned. My gut says they will work just fine for FRC, but I can't guarantee it.

Here is one of those sources.
http://www.thebigbearingstore.com/servlet/the-3735/VW2-dsh-2RS-VW2-dsh-ZZ-VW2/Detail


Both bushings will be in stock in the next day or so.

[taichichuan]

Hey Gang,

What is the load bearing capability of the 1" extrusions? That is, how does it compare with 1" square 1/8" square 6061 aluminum tube? If I've done the math correctly, the Rev extrusion seems to be lighter than the 1" square aluminum tubing. So, I'm trying to determine if it's a better option than welding the 1" tube for a frame.

TIA,

Mike

[GeeTwo]

Loading in what direction?

For most deflection and torsional loading (including buckling), the stiffness depends on the moment of inertia of the cross section, which, for a given amount of material, increases as the square of the distance from the center. For a given amount of material and diameter, a hollow round tube will have the greatest moment of inertia (be strongest), with a hollow square tube being a little bit behind. Shapes like I-beams and rectangular tubes are designed to have a larger moment of inertia in one dimension (the longer dimension) than another to accommodate a larger load in that direction.

For tension loading, I understand that shape makes less difference unless your material forms fibers.

Shapes like the REV and 80/20 extrusion require more weight for the same strength; their purpose is in easy fabrication using tee nuts and similar fasteners.

[Lireal]

For most deflection and torsional loading (including buckling), the stiffness depends on the moment of inertia of the cross section, which, for a given amount of material, increases as the square of the distance from the center. For a given amount of material and diameter, a hollow round tube will have the greatest moment of inertia (be strongest), with a hollow square tube being a little bit behind. Shapes like I-beams and rectangular tubes are designed to have a larger moment of inertia in one dimension (the longer dimension) than another to accommodate a larger load in that direction.

Can you be a little more clear? Which has less deflection, the tubing or the extrusion?

[EricH]

Can you be a little more clear? Which has less deflection, the tubing or the extrusion?
Just to be a total annoyance (and to give you a taste of real engineering):

What's the load case, the size, and the wall thickness? Oh, and how is it supported? You see, the answer depends on knowing those... OK, OK, I'll go a little easier than that.

What he's saying is, essentially, more material at the outside of a piece of material will resist deflection better, given the same mass and size. BUT, extrusion may be tailored to resist deflection better in one direction. (I-beam being one example--it'll bend better if you're trying to bend it in the direction of the open sides than if you try to bend it towards the flanges.)



Moment of inertia (and in this case, that's MASS moment of inertia) is something you'll tend to hit somewhere around 2nd-year engineering coursework, possibly a hair sooner. It's not that hard in concept; the simple definition works out to how much torque it takes to rotate an object about a given axis. Now, the actual application of that definition, and the formulas to help determine it, are where that gets fun, as the shape of the object in question plays a role (which is why that was brought up in the explanation). If you're interested in running through some of the math, let someone know; that can be arranged...

[GeeTwo]

Can you be a little more clear? Which has less deflection, the tubing or the extrusion?

For a given amount of material and diameter, a hollow round tube will have the greatest moment of inertia (be strongest), with a hollow square tube being a little bit behind.

That is, tubing is the stiffest shape there is for loads which may be required in every direction sideways to the length.

[MechEng83]

Moment of inertia (and in this case, that's MASS moment of inertia) is something you'll tend to hit somewhere around 2nd-year engineering coursework, possibly a hair sooner. It's not that hard in concept; the simple definition works out to how much torque it takes to rotate an object about a given axis. Now, the actual application of that definition, and the formulas to help determine it, are where that gets fun, as the shape of the object in question plays a role (which is why that was brought up in the explanation). If you're interested in running through some of the math, let someone know; that can be arranged...

I'm pretty sure the discussion is about AREA moment of inertia (units of [length]^4). Though your description of mass moment of inertia (units of [mass]x[length]^2) is related to rotational inertia, it's not germane to this discussion.

Regarding OP's question:
We found the extrusion to be heavier than the thin-walled tubing we've previously used for frame elements. Are you possibly referencing 1/8" wall square tubing? If so, I'm fairly confident the tubing is stiffer in bending and torsion than the Rev Extrusion. As far as axial stiffness (along the length) it's going to be proportional to the cross sectional area, which is proportional to the weight/unit length for the same material.

[Greg Needel]

I'm pretty sure the discussion is about AREA moment of inertia (units of [length]^4). Though your description of mass moment of inertia (units of [mass]x[length]^2) is related to rotational inertia, it's not germane to this discussion.

Regarding OP's question:
We found the extrusion to be heavier than the thin-walled tubing we've previously used for frame elements. Are you possibly referencing 1/8" wall square tubing? If so, I'm fairly confident the tubing is stiffer in bending and torsion than the Rev Extrusion. As far as axial stiffness (along the length) it's going to be proportional to the cross sectional area, which is proportional to the weight/unit length for the same material.


FYI the for REV extrusion are as follows.

Cross Sectional Area: 0.38133 in^2
Moment of Inertia X: 0.03394 in^4
Moment of Inertia Y: 0.03394 in^4
Yield Strength: 21000 Lbs./ sq. in (psi)
Modulus of Elasticity: 10007000 Lbs./ sq. in (psi)


The debate as to which is stronger really does depend on your loading conditions and use case. If you are talking in the context of FRC style robots, I highly doubt you will see a notable difference in strength per piece (as small deflections) don't really effect much in this case.

Where you will see the difference is in how you join them. A welded 1x1 tube is going to be better than a piece of extrusion with nuts and gussets, but there again it depends on your use case and for FRC scale applications you can't go wrong with either.

[MechEng83]

FYI the for REV extrusion are as follows.

Cross Sectional Area: 0.38133 in^2 (FTFY)
Moment of Inertia X: 0.03394 in^4
Moment of Inertia Y: 0.03394 in^4
Yield Strength: 21000 Lbs./ sq. in (psi)
Modulus of Elasticity: 10007000 Lbs./ sq. in (psi)



Thanks Greg. Always good to hear specs from the figurative horse's mouth.
I'll file this info away for comparison discussions with my team.

[garyklein]

I will be ordering some of your extrusion and bearings for our team.

I have made a drilling tool for working with robotextrusions, and it has the 5 hole pattern to fit the end of your 1 inch shape incorporated so it will be easy for teams to use it.

You can see it at robotextrusions.com