what type of wheel where you using compliant wheels are awesome on intakes for this very reason
We’re using 1.5” of compression on the front roller of the intake, and 1” for the upper rollers, with ThriftyBot compliant wheels. Our prototypes still had some problems with the ball pushing the intake upwards, so we designed our linkage to mitigate that by pulling the roller back as it moves up. If that doesn’t quite make sense, feel free to check out our CAD for more details, as well as our Open Alliance build thread.
Our Google Photos Album also has several videos of the intake in action.
Hope this helps!
We are using 2" stealth wheels
Looks like a good design. What thickness poly are you using for your intake arms? Also, would you recommend we go with less compression since we are using pneumatics and stealth wheels?
We’re using 1/4" polycarbonate for impact resistance. I’d say 1" to 1.25" of compression should be fine for stealth wheels, and I don’t think pneumatics make much of a difference in terms of compression.
How much have you run this intake? How many cargo through it? See this thread.
We have already run over 500 game pieces through our intakes and what we have seen is that there is severe degradation of the intake and handoffs over a few short cycles. The ThriftyBot Squish Wheels are great - until they aren’t with this game piece.
Also, if you are feeding the balls (not off of the official carpet), it will give you false data. Get the robot on the carpet and attack the cargo. Don’t start by chasing cargo - start with cargo in stasis. That will give you a good benchmark. Then chase the cargo and see how it operates.
It is amazing how different your intake will work in the first few cycles vs. cycles after running for 10-100 times. 4607 has been running ‘driver practice’ for over a week now and we have seen some very unhappy results with many different wheels, compression, diameters, spacing, etc. And depending on the wheels, there has been some siginificant degradation/damage to the cargo. I would expect that Inspectors will be on the prowl for teams that are damaging the game piece. We ‘think’ we have found some of the culprits, but we have not fully negated any one wheel type (but mecanums with too much compression seem to be culprits).
This is all great information. We’ve practiced with our intake for a good few hours now, almost entirely on field carpet, with balls both static and moving. We started noticing some fuzz buildup on the wheels after tonight’s practice but didn’t think too much of it. We aren’t using mecanums anywhere at the moment but we were thinking of adding them to the outside edges of the roller. Probably won’t be doing that anymore after seeing what they do to the cargo.
Overall since our compression is fairly low (1" throughout most of the intake) I’m not as worried about the compliant wheels, but I’ll be sure keep an eye on the wheels after each practice.
What issue are you seeing the mecanum wheels cause? We have mecanum but haven’t noticed any markings, but we’ve probably only ran it 20-30 times.
For the pneumatics I was more wondering about spring/give in the system when intaking. I know they will give a little but wasn’t sure how much
Also, we have some poly that is around 1/8 (.107 maybe?) would doubling it be sufficient or is it bad to double the sheets?
For the intake speed I understand you want to be about 1.5 x faster than drive speed. Is that based on loaded speed or unloaded speed for the intake?
It’s generally best to look at free/unloaded speed - loaded speed is highly dependent on the way you build it.
Also, it might be helpful to you to intentionally gear it a bit faster than you think you’ll need (~1.75-2x robot speed). That way, it gives you some overhead to adjust the intake speed using programming; if you gear your intake fast and find that it’s a bit too fast, you can just slow the motor down in code (and the small loss in motor power isn’t critical for an intake). If you gear the intake too slow, however, and want it to go faster, you’ve got to rebuild it with a different gear ratio.
makes sense. In the JVN calculator with 10lbs of drag we are seeing a 276.0 in/sec (23 ft/sec) unloaded at 10:1 and 690.1 in/sec (57.5 ft/sec)at 4:1. I feel like the 4:1 is overkill, but not sure. Would you recommend the 10:1 or 4:1 in this case?
Ha of course it would be a ratio we don’t have! Closest we could get would be 9:1
Definitely not the 4:1. Again, the sweet spot for intakes is generally somewhere between 1.5x - 2x your robot speed. Assuming you’re geared for ~13 ft/s, both the 9:1 and 10:1 get you decently close to that range.
I suspect you’re using a VersaPlanetary though - in that case, just chuck a ratio on and test it. If you try it out and want to change the ratio, you won’t need to remanufacture anything.
Yeah we are using the versa. We just got them in today so we will try them out. We just wanted to get a good idea of a starting point before we built one. Do you know what a good drag load is for an intake to base our calculations on?
If you’re using the intake free/unloaded speed to get your starting values, drag load doesn’t matter. Again, it’s usually not worthwhile to estimate drag load before building your intake… or after.
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