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The bumper brackets are awesome Greg! Very similar to how Celt-X does ours. One tip - we found that these âpeel rivetsâ work a bit better than wood screws to attach the bracket to the plywood (less risk of over-tightening and stripping). Theyâre faster too!
Have you checked to see how these brackets fit on MaxSwerve and other swerve module frames?
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Have you thought about using T-nuts installed on the outside of the plywood and then using flathead bolts threaded into the T-nuts? We used this method for our in-house mounting brackets and it was very robust. Looking at your picture, a #10 T-nut would have a lot more pull-out area compared with those peel rivets.
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The reason thatâs worse is that you have to line up the holes for the tee nuts before stapling the fabric, but the fabric will change the alignment. Even worse, itâs pretty easy to push the tee nuts out of their holes if youâre not careful installing the bolts.
The nice thing about wood screws or peel rivets is that they can be attached after the upholstery is done
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Yeah, true. We did have to get everything lined up with just the bare wood. We used washers to create a small gap to simulate the fabric thickness. And then we needed to find the holes again after we put the fabric on (we were using Dacron sail cloth at the time so once we felt the hole with our fingers, we could use a soldering iron to melt the hole to match the drilled hole size in the wood). It seems like with these corner brackets you are going to need to get the location pretty precise anyway to get it to line up with the frame. So those aspects of the fit up seemed like they would be equally tricky whether you did it before or after fabric. But I do see the value of being able to do the work blind after the fabric goes on.
REVâs instructions for these actually recommend mounting the bumper brackets to your chassis first, lowering your mostly assembled bumpers over the chassis/brackets next, and then match drill/screw the bracket into the bumpers while everything is in place.
This is similar to how we installed our bumper brackets the last 2 years, and makes things pretty easy to ensure everything will line up when youâre done.
This is pretty dangerous advice to hand out without cautioning that these rivets have essentially no impact strength compared to an alloy bolt.
If teams are making good bumpers that rely on full face support of the wood, thatâs not a problem⌠but most teams are hanging their bumpers off mounts and their fasteners are quite stressed. Iâve repaired bumper attachments on partners in just about every elims run recently.
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We normally do all our bracketing before the upholstery, doesnât feel like a big deal.
If we needed to work blind, I can see how the t-rivets might be stronger than wood screws - do you think they would hold in a location where a woodscrew has already spun out, in a repair context?
We do all the bracketing before upholstery so we can test fit the frames and find problems before the fabric and staples. We also use zinc or steel threaded inserts in the wood so that we can replace brackets easily, but the hold is much better than wood screws.
The comparison was with a wood screw, which only has a moderate grip strength itself. If the issue is weaker fasteners (like rivets or screws), the answer is use many of them. Revâs brackets use 14 per corner, which is plenty.
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Ah, you confused me with tee nuts. I wasnât familiar with tee nuts that wood screws screw into.
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Could you offer a way to buy just a Ultraplanetary gearbox? Currently the only options are buying individual cartridges or also getting the HD hex motor. Thank you!
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I mean, while I understand the frustration of having a bunch of extra HD Hex motors around, the $45 bundle is still a great value. The cost individually for parts in the kit minus the motor is like ~$60 (~$80 if you include the motor), meaning the motor is effectively free, and the gearbox is still like $15 cheaper than buying the parts ala carte.
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Sure, but itâs a real pain to extract the pinion and use it on another motor. I would love to have a similar kit pre-built with Neo 550s.
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Perhaps they could just include an extra pinion or two in the kit? I canât imagine those are terribly expensive to make.
They do include extra pinions.
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When the Flex Dock comes out will the counts / rev be different when connecting a regular NEO or 550 to the Spark Flex (7168 / rev) or will it still be 42?
Hello REV! This year we did a ZebraPower style battery with 2awg cables with SB120 connectors. The PDH currently only supports up to 4awg connectors (and trying to stuff a 2awg wire into a 4awg sized slot is not the most fun thing to do), and would love to see 2awg (900, us, and many more teams) or even 1awg support natively (for teams like 401).
We currently run 2awg cables going from the battery into the main breaker and then 4awg from the main breaker into the PDH. This is leaving some battery performance on the table.
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REV most likely wonât be able to accommodate anything bigger than 4awg due to the WAGO 2616 connector. The 2616 connector is rated for 18 - 4 awg. I donât think WAGO has anything that can support 2awg. If they did, REV would need to redesign the PDH slightly to be able accommodate the bigger size of the connector.
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There really isnât much âbattery performance left on the tableâ.
- The best lead acid batteries have internal resistances above 12 milliohms.
- The resistance per thousand feet of copper wire is listed here. Lets say you went crazy and put 8 feet of battery lead on your robot, that amounts to 0.0032 ohms for 6ga, 0.0020 ohms for 4ga, and 0.0013 ohms for 2ga. (an order of magnitude smaller than the battery)
- That means the best case current you can draw out of the battery before brownout is (12.7v - 6.3v) / (0.012 ohm + wire resistance + connector resistance):
- with 2 gauge wire thatâs ~= 481 amps.
- with 4 gauge wire thatâs ~= 457 amps (5% less)
- with 6 guage wire thatâs ~= 421 amps (12% less)
Those are really marginal gains, in very optimistic scenarios. In reality youâll probably want to be current limiting your robot to (much) less than 300A to prevent brownout at the end of the match (when the battery voltage drops below 12v) and at the end of the season (when the battery resistance creeps above 20 milliohms).
Furthermore, most teams will use far less than 8 feet of battery lead wire, which means itâs even less important relative to the battery internal resistance. Note that 8 feet of 2 gauge wire weighs 1.6 lb, compared to 0.6 lb for 6 gauge wire. Since acceleration is proportional to weight, the 2ga wire would cause a 0.7% (1 lb/150 lb) decrease in acceleration performance right there 
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