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Looks good. Regarding your actuator dilemma, have you looked at the GLA200 from Gimson? https://gimsonrobotics.co.uk/categor...inear-actuator It's only a little over 100mm long when retracted so with a 100mm stroke would be a little over 200mm. I use one on my bot Neophyte which has a grabber configuration & although you won't be crushing anything it does have enough force to keep a hold of bots. They also do the GLA750 version which is a little slower but has much more force behind it.
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Unless I'm misunderstanding the drawing on the Gimson website, that actuator is [stroke length plus 105] mm long when retracted. That means 205 mm for a 100 mm stroke, or 305 when extended, which is still a bit on the long side to fit. We could probably bodge it in somehow but it feels... suboptimal.Comment
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Personally, I think the method you suggested would work as per the CAD diagram you posted You'd want a multi-stage spur gearbox to make it work rather than a planetary if horiztonal space is an issue.Comment
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That is correct, 205mm for a 100mm stroke. However the actuator will stop itself if it is unable to move to it's maximum extension, so you wouldn't need to worry about making the full 305mm fit. Alternatively if it's the body that's too big, you could get an actuator with a smaller stroke & attach an extra piece to the mechanism to make up the rest of the distance.Comment
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Unless I'm missing something, there's no stopping mechanism in the actuators apart from the limit switches at the end. So if the actuator is not at the end of its travel and power is still applied, the actuator will try to force itself onwards, possibly damaging itself and/or the robot.However the actuator will stop itself if it is unable to move to it's maximum extension, so you wouldn't need to worry about making the full 305mm fitComment
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As far as I'm aware, you're right about there not being a specific stopping mechanism Jamie. When I've tested Neophyte in the past with the locking bar in the actuator has simply stopped, which I presumed was what was supposed to happen when the actuator couldn't move. After the test the actuator has always worked perfectly fine (although at 200N it is a relatively low powered actuator). All this is just my personal experience with my actuator, if you or anyone else knows something I don't or has their own experiences by all means let me know, thanks.Comment
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Ahh yeah, 200N is only about 20kg so it's more a lack of power that'll be stopping it. The ones I've had in those situations have been 75kg and above, and that's when things can start to get unhappy
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Thanks for all your thoughts folks!
The problem with the Gimson linac is that either the retracted length is too much, or the stroke too small. So either the butt end of it sticks out of the back of the robot, or it doesn't move enough to close the jaws with any real force. Still, I might try a rough attempt incorporating the Gimson one into the CAD model just to see if I can make it work. Always nice to use something off the shelf if possible.
@Ocracoke - the drill gearmotor isn't too long with the planetary box - about 130 mm from end to end which fits in the space fine. The leadscrew + associated gubbins will be about the same size so it's not a problem as long as they're on top of each other.Comment
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Hmm... if the jaw is for clamping, I guess using a drill motor would be enough but won't have much in the way of crushing effectiveness though I guess that isn't what you are going for. The threaded screw will increase torque anyway. I can see this working. :PComment
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Hi all! I've been meaning to update here for a while and keep getting distracted. Seems I'm more organised when it comes to building the robot than I am at writing posts about it. Sadly that does NOT mean I'm very organised at building.
Since Robodojo is in less than a week, however, we've had to actually start doing some work on Wedgeley. We decided to go down the home-made linac route because really, how hard can that be? [Narrator's voice: actually quite hard].
This was a very rough mock up of the whole mechanism:
Or, in animated form:
https://www.youtube.com/watch?v=27WsDYoeOP4
https://www.youtube.com/watch?v=zjIAeJ4qRhg
(links because the forum still seems to be borked...)
The next step was to transfer this to a more substantial material. With that in mind, I tried my hand at CNC'ing a few parts:
This was reasonably successful although it took a while as I didn't really have a clue at the start. The key bit was getting the Argos motor to fit right, and that was OK:
If there's one thing I've learned from repeatedly binge-watching Scrapheap challenge, it's to NEVER EVER use chain drives for anything when you're bodging, so with that in mind here's the chain drive from the motor to the leadscrew for the linac:
Meanwhile, in a curious form of progress, Becky and Simon stripped down Wedgeley Mk I to the bare bones, to replace most of the panels, motor restraints, etc.. I am looking forward to a future where we make robots with MORE SPACE IN THEM.
Various internal changes have been made, slightly less badly fitted panels have been produced, and we now have some steel to clad the front of the wedge. The linac is mostly assembled now, so we just have to cobble together an upper jaw mechanism and the crusher (which will undoubtedly destroy exclusively itself if ever called upon to crush anything more substantial than a coke can) will be complete:
Thankfully I've got Friday off work next week, so we have TWO WHOLE DAYS LEFT to do that.
Cheers!Comment
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Neat write up, looking forwards to potentially seeing this at RoboDojo one day.
Did you use a chain drive as a defined weak spot in the mechanism in case the stresses are too much and/or for weight saving purposes?If there's one thing I've learned from repeatedly binge-watching Scrapheap challenge, it's to NEVER EVER use chain drives for anything when you're bodging, so with that in mind here's the chain drive from the motor to the leadscrew for the linac:
Hahahahaa, I know the pain of building inside very tight spaces with quite thick wires. Right faff to get all the wiring into Jibril (and Azriel on the evidence of what I have put together so far) with all the cables everywhere.Meanwhile, in a curious form of progress, Becky and Simon stripped down Wedgeley Mk I to the bare bones, to replace most of the panels, motor restraints, etc.. I am looking forward to a future where we make robots with MORE SPACE IN THEM.Comment
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This is looking really great! I am especially excited to see how your custom linac turns out - my design was absolutely too complicated for its own good. You say bodging it with chains can lead to problems, but I found making a compact, custom gearbox for a linac to be an absolute nightmare. I think you are much better going this route.
I also love all the linkages involved in your weapon mechanism. Looks too cool when it's in motion like that. Good luck for Robodojo!
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Oooh yeah that's actually a plausible excuse, I will keep that in mind when it falls to piecesDid you use a chain drive as a defined weak spot in the mechanism in case the stresses are too much and/or for weight saving purposes?
The wiring is the worst part, yes. I am used to using at most 20 or maybe 18 AWG wire at work and it's not the same at all... Next time however we will at least make space to accommodate the actual components (it was a close thing getting the ESC and battery into Wedgeley due to the not-very-thorough planning).Hahahahaa, I know the pain of building inside very tight spaces with quite thick wires. Right faff to get all the wiring into Jibril (and Azriel on the evidence of what I have put together so far) with all the cables everywhere.
Thanks! I did toy with the idea of extra gearing to connect to the drill motor, then direct drive the grabby jaw from that with a chain or something. I quickly abandoned that as soon as I realised how many holes would have to be drilled in the right place....This is looking really great! I am especially excited to see how your custom linac turns out - my design was absolutely too complicated for its own good. You say bodging it with chains can lead to problems, but I found making a compact, custom gearbox for a linac to be an absolute nightmare. I think you are much better going this route.
I also love all the linkages involved in your weapon mechanism. Looks too cool when it's in motion like that. Good luck for Robodojo!
Hopefully by the weekend we'll have a video of the actual thing moving and made of metal...
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Quick question of anyone has any thoughts... I'm not sure what would be the best way to implement a locking bar for this weapon, is it won't have a default position where you can slide something in to stop it deploying unlike an axe or a flipper, say. That means it would have to be actuated to the picking position at the end of each fight to line up the locking system, which may not always be possible. Anyone have any tips for locking a slow-moving weapon like this?Comment
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Ugh, sorry for the many typos, which I now can't correct as the forum won't let me edit....Comment
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