A message from REV Robotics

[FTC5110]

Originally Posted by Greg Needel

They are not available yet, but will be available at either AndyMark and/or our new Amazon store front when it launches.

If international teams need parts we are also willing to work directly with you to find the most cost effective way of delivering them.

Excellent and glad to hear you're thinking beyond the US.

But wait just a sec. 8mm hex doesn't seem to be very common. Were you planning on releasing any 8mm hubs because without them I'm afraid there's little purpose for an 8mm hex output shaft. The plastic gear kits look interesting but to be honest without being able to couple metal sprockets and gears to the motor it's pretty limiting.
Shame it's not 0.375" hex because that's off the shelf already https://www.servocity.com/html/hex_b...ping_hubs.html
http://www.andymark.com/product-p/am-2231a.htm

[Greg Needel]

Originally Posted by FTC5110

Excellent and glad to hear you're thinking beyond the US.

But wait just a sec. 8mm hex doesn't seem to be very common. Were you planning on releasing any 8mm hubs because without them I'm afraid there's little purpose for an 8mm hex output shaft. The plastic gear kits look interesting but to be honest without being able to couple metal sprockets and gears to the motor it's pretty limiting.
Shame it's not 0.375" hex because that's off the shelf already https://www.servocity.com/html/hex_b...ping_hubs.html
http://www.andymark.com/product-p/am-2231a.htm

The decision to go with 8mm hex was actually a long and complex one. I am happy to share our thinking.

• Metric parts - thinking about the system we thought about it from a global perspective, and while some parts may be a bit less convenient for standard teams/countries it is far more accessible than teams metric base countries.

• Resolution of 3D printers - even with the lowest price 3D printer you can print the 8mm hex hole with enough accuracy to make functional parts. This would have been possible with 3/8 or 1/2 also.

• Compatibility with existing parts - Most teams that compete in FTC use and have Tetrix parts. All Tetrix wheels and gears have an 8mm round hole in them and then you use adapters to connect them to either 6mm (motors) or 4.7mm shafts. Since an 8mm round shaft will pilot inside an 8mm hex it makes it easy for teams to use their existing adapters, shafts, gears, and wheels in conjunction with our system. Additionally if teams want, they can get an 8mm hex broach and convert their old parts without a problem.

• Sleeve adapters - most of the motors that are already in the hands of teams have a 6mm output shaft. One of the products we will be offering is a metal sleeve adapter that goes from 6mm D to 8mm hex, allowing teams to convert their existing motors

• Common stock - 8mm hex is a common size in both aluminum and steel in most places around the world.
  

We know that it won't be perfect for everyone, but we did our best to try and consider that the majority of existing teams re-use their parts every year, and we didn't want to force anyone into another closed system. For new teams we will have many adapters and hubs available (either for sale or download) to help make using any existing parts work. Our system will stand on it's own where we will have everything that a team will need but we also make it a priority to play nice with others


Greg

[Richard Wallace]

Originally Posted by Greg Needel

The decision to go with 8mm hex was actually a long and complex one. I am happy to share our thinking.

• Compatibility with existing parts - Most teams that compete in FTC use and have Tetrix parts. All Tetrix wheels and gears have an 8mm round hole in them and then you use adapters to connect them to either 6mm (motors) or 4.7mm shafts. Since an 8mm round shaft will pilot inside an 8mm hex it makes it easy for teams to use their existing adapters, shafts, gears, and wheels in conjunction with our system. Additionally if teams want, they can get an 8mm hex broach and convert their old parts without a problem.

Greg

I don't see the detailed specs for REV's 8mm hex -- maybe I have not looked hard enough yet?

Anyway, a quick search indicates that 5/16" (0.3135" finished dimension) hex broaches are available from popular distributors MSC Direct and McMaster-Carr at about one-third the price of an 8mm (0.3154" finished dimension) hex broach. About $130 for 5/16" vs. about $400 for 8mm.

What is the actual size of REV's 8mm hex shaft? Will 5/16" work?

[jman4747]

Originally Posted by Richard Wallace

I don't see the detailed specs for REV's 8mm hex -- maybe I have not looked hard enough yet?

Anyway, a quick search indicates that 5/16" (0.3135" finished dimension) hex broaches are available from popular distributors MSC Direct and McMaster-Carr at about one-third the price of an 8mm (0.3154" finished dimension) hex broach. About $130 for 5/16" vs. about $400 for 8mm.

What is the actual size of REV's 8mm hex shaft? Will 5/16" work?

Aluminum 8mm hex shaft on MMC has a tolerance of +/- .23mm. That would be .3059in - .3240in. Steel 8mm hex has a tolerance of -0.05mm. Thus 8 - 7.95mm or in inches that's .315 - .313.

[Richard Wallace]

Originally Posted by jman4747

Aluminum 8mm hex shaft on MMC has a tolerance of +/- .23mm. That would be .3059in - .3240in. Steel 8mm hex has a tolerance of -0.05mm. Thus 8 - 7.95mm or in inches that's .315 - .313.

Yes. So if REV gets their 8mm hex shaft stock from MMC it will not fit in a hole made using a 5/16" broach.

However, MMC is not the only source for hex shaft stock -- for example, FRC teams generally have a much easier time fitting hex shafts into broached holes if they buy their shaft stock from VEXPro.

So again, what is the actual size of REV's 8mm hex shaft?

[Greg Needel]

Originally Posted by Richard Wallace

Yes. So if REV gets their 8mm hex shaft stock from MMC it will not fit in a hole made using a 5/16" broach.

However, MMC is not the only source for hex shaft stock -- for example, FRC teams generally have a much easier time fitting hex shafts into broached holes if they buy their shaft stock from VEXPro.

So again, what is the actual size of REV's 8mm hex shaft?

Let me start out by saying that tolerance stackups are a challenging kind of fun, especially when you are dealing with different manufacturing methods, materials, and suppliers.

When we chose 8mm we were aware of how close 5/16 was to 8mm and did consider that teams might want to use that instead. From the cost of the broach perspective we actually have sourced 8mm broaches that are much lower cost and may start to sell them if it seems like there is a demand.

The answer to the question at hand is actually in 2 parts. The size of our standard holes and the size of our shafts (motor and axle).

Our basic aluminum axle (made by extrusion) is dimensioned as 7.95mm +0/-.15 (or in inches .307 - .313)

Our basic hex hole (which is mostly used in plastic) is dimentioned as 8mm +.25/-0 (or in inches .315 - .325

This means our minimum fit tolerance is .05mm (.002 in) and our max range is .45mm (.018 in). The max range is kind of deceiving, because of some of the tuning we will do in our plastic gears to get a good fit.

With these tolerances the 5/16 broach from mcmaster will be fine, along with the steel shafts at both 8mm and 5/16. The Aluminum 5/16 shaft from mcmaster will most likely work most of the time (but not guaranteed) and the aluminum 8mm shaft is to wide of a tolerance range to actually predict, but the ones that came when I bought some measured at 7.93mm

All of the gears and shafts are still about 6 weeks from launch (as we are going to launch them all at once) so there is still the possibility of some of this changing, although I doubt it.

[Richard Wallace]

Originally Posted by Greg Needel

Let me start out by saying that tolerance stackups are a challenging kind of fun, especially when you are dealing with different manufacturing methods, materials, and suppliers. ...

Thanks, Greg. This is what I was looking for.

Will watch your site and AM for launch, and order some parts to play with.

[Richard Wallace]

Originally Posted by Greg Needel

All of the gears and shafts are still about 6 weeks from launch (as we are going to launch them all at once) so there is still the possibility of some of this changing, although I doubt it.

How are preparations for this launch progressing? I don't see the gears and shafts on your site now.

[Greg Needel]

Originally Posted by Richard Wallace

How are preparations for this launch progressing? I don't see the gears and shafts on your site now.

These things are still in progress, we were not happy with some of our preliminary outcomes so we are working through some technical difficulties. That being said, we had to shift some of our resources both mental and financial to some of our FRC products (namely the SPARK motor controller), which has put some of them in a holding pattern waiting for some attention.

At this point I can't give an exact date for the release of these products, and would not hold out for them for this FTC season. We have always had the date of April 2016 in our books for a full kit release, which includes all of these parts & more. That is still our main target date, but we were hoping to release some for early adopters sooner, like what we have done for the brackets, linear motion parts, and extrusion.

If there is anything specific you are looking for I may be able to provide you with some pre-production samples to evaluate but we are still quite away from a full product launch. I am really sorry about this, and hope that no teams were waiting directly for these products. We wish we were farther along than we are, but also wont sacrifice quality for speed in this case.


Greg

[Greg Needel]

Originally Posted by Gdeaver

The programmable servo is listed under FRC. I believe those specs are over the FRC limit of 4 watts. I get 10.68 watts. Until there is a season that FRC changes the 4 watt limit, Maybe it should be listed under FTC only.

By now you guys may have noticed that FIRST has changed the ruling on servo legality (allowing any COTS servo) so the REV Servo is now legal for use on FRC bots.

From the blue box for R29

For servos, note that the roboRIO is limited to a max current output
of 2.2A on the 6V rail (12.4W of electrical input power). Teams should
make sure that their total servo power usage remains below this limit at
all times.
This is the total number of each motor a Team may use on their
ROBOT, not the quantity per part number. For example, each team
may use up to six (6) CIM motors on their ROBOT, regardless of the
quantity or combination of each individual part number used.
Given the extensive amount of motors allowed on the ROBOT,
Teams are encouraged to consider the total power available from the
ROBOT battery during the design and build of the ROBOT. Drawing
large amounts of current from many motors at the same time could
lead to drops in ROBOT battery voltage that may result in tripping
the main breaker or trigger the brownout protection of the roboRIO.
For more information about the roboRIO brownout protection and
measuring current draw using the PDP, see RoboRIO Brownout and
Understanding Current Draw.

So when choosing servos (including the REV one) just make sure you understand the power consumption involved.

[FTC5110]

Hey Greg, When do you anticipate having the REV-41-1097 Servo back in stock? Asking here on CD so others see the response and don't eat up your time enquiring directly.

[Greg Needel]

Originally Posted by FTC5110

Hey Greg, When do you anticipate having the REV-41-1097 Servo back in stock? Asking here on CD so others see the response and don't eat up your time enquiring directly.

There has been a huge demand on these servos in the past two weeks and have wiped us out. We have more on order, but it won't be for a few weeks until they arrive. I will post an exact date when we know for sure, but I am trying for the end of the month, but it likely will be the first week in April.

[ehochstein]

Originally Posted by Greg Needel

There has been a huge demand on these servos in the past two weeks and have wiped us out. We have more on order, but it won't be for a few weeks until they arrive. I will post an exact date when we know for sure, but I am trying for the end of the month, but it likely will be the first week in April.

Hard to imagine why there is such a high demand for this AWESOME product. Thanks for everything you do to get these to teams, Greg!