If you want nice smooth edges after cutting, use a sharp block plane to get a glassy smooth finish.
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If you want nice smooth edges after cutting, use a sharp block plane to get a glassy smooth finish.
After having looked into a name-clash with one of dragonzrmetal's bots, I'm changing this robot's name to Rampart. That had better not be taken by someone too. :P
Hardox parts arrived today from Kcut! Super pleased with the quality, but I do need to order again, since I meant to get a pair of two of the parts, but I don't think I made it clear enough. Also, some filing shall have to be done to remove a couple of the burrs and make the holes a little bigger. I'm gonna try and get the HDPE chassis done soon, but I'm still waiting on T-nuts I ordered about three weeks ago that were just sent. :I Anyway, I'm most impressed with the look of this shovel. It's gonna give me plenty of much-needed protection up-front. :>
Attachment 5824
Looks really good! Are you using an actuator for the arm :)
I am indeed, that part in the bottom-right is the new mounting bracket for it. Into that will fit the brushless motor and the linac (minus its original gearing and motor), and I'll drill some holes and add some of these new gears in, which are a decent amount bigger. I'm planning on having another plate on top to sandwich them in, but that can just be cut out of the same steel sheet I'll be using for my side armour.
That's really impressive. Is the actuator going to push directly on the arm itself or through an axle like biohazard?
It's pretty much direct - you can see how it works here, and probably spot the parts:
http://i.imgur.com/hetwxg1.jpg
Oh wow. Which software n file types did u use to get the bits cut? Did u just email them the stuff etc.
I made the parts in Sketchup, and then converted them to .DXF files with a plugin. If you have Sketchup Pro, you don't have to use a plugin, but you have to pay for pro. I put the files in my Dropbox and emailed links to Kcut, along with some extra screenshots and information on where to fold the bits that needed to be folded, and that's about it.
thanks, wondering that myself
From experience, Kcut will work from Paint pictures and even vague hand gestures if you can't CAD!
I've been trying to disassemble my linac so that I can find some points to screw it onto the new mounting plate, but I can't seem to be able to get the old one off. I can take the bottom cover and the gears out, but the top half seems stuck to the main barrel of the actuator, almost as if it's glued there. I've taken out all the screws I can see, anyone know how these things come apart? The only other thing I can think of is the nut connected inside the barrel, visible if you unscrew the bar, but I can't get that out yet because I don't have the socket to reach inside.
This is about what mine looks like, and basically I just want to ditch the motor and the entire assembly attached to it, just leaving the main barrel:
https://www.apsoparts.com/ap/catalog...1787IM_tif.jpg
I have a very similar linac and the same goal. Here is a picture of my linac with the tube removed; it had three screws around the base of the tube and after they were removed, the tube was a tight fit on the base but could be pulled off.
http://www.nswrfc.org/Nick/P4140612.JPG
If your linac doesn't have any screws at the base of the tube then it probably IS glued in. The big problem in discarding the base is that it holds the thrust bearing that keeps the acme screw in place. If you ditch the base, you will have to make a new bearing housing and find some way to keep it centred in the end of the tube. That's not an easy task to do well and just bodging it will probably lead to a quick failure.
My plan so far is to keep most or all of the original base and attach a new aluminium plate to the back of it. The new mounting plate can be as large as needed to mount the motor.
Just thought I'd check in here. All the Hardox parts have now arrived, along with some cobalt drill bits and cutting paste for cleaning up the holes. Anyway, I've been working on cutting the HDPE. Progress is slow but steady, and these bits are a lot neater than the first test piece. I've got about 30-40% of the chassis done so far, and I think I have all the fixings I'll need. You were right about the block plane, Overkill, that does leave a nice finish. I've also bought a 35mm Forstner drill bit, to hopefully drill out some nice, clean holes for my motor mounts (which will be made out of parts of the chassis). However, I've found a decent way to make holes in the outer parts of the chassis, where the 'nose' of the motor gearbox has a resistance fit. That should hopefully stop them rotating even if the motor mounts do become loose on the inside. Plus, I can screw the old metal plates from the drills onto the other side to keep the motor in. Because I'm terrible at explaining things, just have a look at the image below. I've tried my best to take the linac apart again, and I just can't separate the main barrel, or even the outer tube from the base. I think I'd have to grind or hacksaw it off if I really wanted to. But I think given your advice, Overkill, I'm gonna try and just screw the slightly modified base onto my mounting bracket, and take it from there. But anyway, getting the main chassis and locomotion running first, still got to alter the wheels so that they sit nicely on the motor axles. More updates soon!
http://i.imgur.com/njKsN1D.jpg
http://i.imgur.com/YjkLccq.jpg
Ok, admittedly 'soon' should've come with a big disclaimer. Regardless, progress has been made, and here's a few photos. Hoping to get the (already completed) electronics inside and the wheels on in the next few days, then it's time to work on the weapon, but I'll post a video as soon as the base is mobile. No promises when this time though. :P
Attachment 5994
Attachment 5995
Aha! And today, the promised update! The base of the robot is now fully functional, and could just about qualify as a rambot. That said, it's by no means complete. The body itself will be rounded out, tracks will be added, and most importantly the lifter weapon will be assembled. Obviously plenty of cable management inside still needs to be done, and I still need to add in a removable link and a switch for convenience. That said, what I currently have will drive around just fine and is quite nippy, despite looking like a bad version of King B. I filmed a very short demo, sorry it's poor quality and I even get my feet in the shot at one point. :I But yeah, I'll film some more when I'm at a further stage of development with it. I didn't have the mixing quite fully figured out until after I filmed this, hence why the driving is a little wonky.
https://youtu.be/cxqU0nFmEeE
And here's an image of it as of right now:
Attachment 6015
By the way, anyone got any tips for removable links? How do I make it accessible while not really easy to knock out? And what should I use for it?
Did u melt nuts into the wheels?
That's my backup plan, but for the moment I just drilled out and tapped them with a 3/8 UNF thread, and I'm keeping them on with the screw from the drill motors and a washer. It works quite well. If the plastic in these goes threadbare, I'll just have to press the nuts into them, but honestly I might get some better wheels if that happens.
Looking really cool, man! :) Interested to see how your tracks will turn out. Haha, you're still making much quicker progress than I did - went about a year without posting anything on my thread!
Maybe it's just me, but I thought it was awesome to use these badass looking controllers that looked so complicated on TV when I was a kid... and then only use like 2 functions on it. :p
Thanks dude, I hope we get to fight some day! And yeah, it is a bit odd using so few functions on the transmitter, although I imagine machines like Pressure use a fair few more. :)
No notable progress since last update, but I have been thinking. As you might know, I'm converting an already-existing linear actuator for my lifter, and I'll be using a brushless motor. One of the problems I'm facing however, is limit switches. I'm pretty sure the way the current limit switches in the linac work is that when depressed, they divert the current through a diode, meaning the motor can only run the opposite way until the switch is released again. This is obviously fine for a brushed motor, but since a brushless motor has three leads which require the timed input from the ESC, I can't use that. Basically I want it so that when the linac reaches its limit, the motor stops, and can only run in the opposite direction.
Now the idea I came up with today was to create a separate little board which switches two of the input wires to the motor (with a FET or something) when either switch is pressed. As far as I know, this should make the motor run in the opposite direction until the switch is released, and then switch back. I'm unsure about this for a couple of reasons though. One is that this will probably make the linac jitter at its limits, depending on the switching frequency, positioning of the switch, etc. This wouldn't be so bad on its own, because all I really need the switches for is stopping the gear system or motor from being damaged, they'd just be a safety measure in case I didn't take my hand off the transmitter in time. But the other thing is, when this 'jittering' is happening, would the quickly changing current fry the board and/or my motor? Otherwise, does anyone know how to integrate this kind of one-way limit switch behaviour for a brushless motor? I don't quite want to go to the lengths of making a custom ESC just yet, this is still my first robot after all. I also don't want to have my actual ESC turn off at any point, since there's a startup time in which the weapon would be inoperable. Has anyone got any ideas?
Cheers guys.
I'm sure I researched this very thing, and what I discovered was that reversing two of a brushless motor's wires while it was spinning wouldn't change much; it would just keep spinning in the same direction until it stopped. As far as I'm aware there's no way to do it outside of using a separate microcontroller board (such as an Arduino) to modify the RC signal sent to the ESC when the limit switches are depressed. I had also considered that if the microcontroller on your ESC has unused pins, you could probably program some new firmware to accept the limit switch inputs on these pins and react accordingly. I would definitely be interested to hear if there's a simpler option, though.
Edit: Found the source of what I wrote above: http://www.robowars.org/forum/viewto...dc16f453#88220
Another option is to turn the system into a giant servo by adding an Arduino and a potentiometer as discussed here: http://www.robowars.org/forum/viewtopic.php?t=2215. In this thread we are talking about using a brushed winch motor but it will work just a well with a brushless motor. You can alter the code to work with limit switches without too much trouble.
Thanks for the advice guys. It doesn't sound easy, but I do like the idea of using an arduino to intercept the RC signal. Looks like I'll need to do some research. As for the 'unused pins' idea, I have the stuff to program ESCs, but I have no real idea how hex files work. I could give it a try though. I guess there's always the alternative of adding some sort of slip clutch in the gearing, but I can just imagine that breaking and rendering the weapon useless in the middle of a fight.
-Edit:
Found some resources, I'll put them here for later and anyone else that reads this in future. Looks like this isn't as difficult as I thought.
https://www.sparkfun.com/tutorials/348
http://rcarduino.blogspot.co.uk/2012...iver-with.html
Been working on the arduino stuff, getting there. It's easy enough to read the input and print it out to serial, but I'm still struggling to output and make the ESC act on that. Regardless however, more importantly is that I sort out the actual connection between the new motor and the linac. I'm not sure how I'm gonna do it. The brushless motor I have is STUPIDLY fast at full tilt, so I need some heavy gear reduction. The current linac gearbox has plenty of gearing which I think should stand up to the force from the motor, provided I get the limit switches working, however I'm going to need some spare gears if I'm going to even start connecting it. I've measured the gears inside, and on one with a 1 and 1/8th inch diameter and 50 teeth, I've calculated a pitch of 44-ish, so a modulus of 14. Does that sound correct? Thing is I can't seem to find any 44 pitch gears online - am I doing this wrong somehow? I thought about using a belt which would hopefully reduce damage if the motor is still running at the linac's limit, but I wouldn't get the reduction ratio I need to decrease the speed sufficiently in any kind of reasonable space. A really solid and compact option would be a worm gear, but the motor's kinda at the wrong angle for that. If I can finally work out a gear arrangement I can get a gearbox/mounting plate cut out of aluminium, but I'm struggling to even find gears that fit - any ideas? Am I doing something wrong?
I can't make head nor tails from your description of the gears you meassured.
It's the Imperial DP (how many teeth on pitch of 1" diameter.) or DIN standard module.
Ok, sorry let me try to be clearer. I measured the diameter of a 50-tooth gear (excluding the teeth) to be approximately 1 and 1/8th of an inch. So to find out how many teeth on one inch, I divided 50 by 1 and 1/8. This gave me around 44 for the pitch. Is that correct? Sorry if I sound clueless, this is the first time I've worked with this kind of mechanical engineering.
I'm baffled how expertly you can convey confusion in this. :)
Lets start.
You need a gear with 50 teeth, and with an outside diameter of about 29mm .
The 2 common "types" of gears are Imperial DP or Metric Module.
if I use the WAG methode, I get these results.
Metric
Mod 0.5 Z50= OD of 26mm
Mod 0.6 Z50= OD of 31mm
DP 44, that's a non excisting size. It jumps from 32 to 48.
2 possibilities.
1) meassure again to get better values.
2) it's a custom size gear.
Is it not just easier to buy a bigger lin ac?
Daveimi:
No. Way back when I was searching for linacs, I couldn't find one that gave enough force and moved fast enough. So I bought the one I have now, which can lift about 20 kg, but is slow, and then I built the robot around that. The distances between the end of the arm and the brackets I had cut are all set to fit the linac I have.
Maddox:
I was using this to calculate DP: http://www.robotpark.com/academy/LR/..._ROBOTPARK.png
I'll try measuring again, honestly the most important piece of information there is that DP 44 doesn't exist. But if I'm working out the pitch correctly, I don't understand why I seem confused to you. A 'yes' or a 'no' to that would've been most helpful. :P
Edit-
I measure approximately 29mm/50 = 0.6 metric module (rounding here) for the gear. This sounds more likely. I suppose I'll try buying a cheap 0.6 mod gear to see if it meshes, just to make sure.
http://i.imgur.com/cp2ZCnd.jpg
http://i.imgur.com/MTpPsSX.jpg
Hi Rory, just reading up on your build to get some ideas for mine (which even start until after xmas at this rate) and its good stuff.
For your linac problems - I'm not sure I understand the whole situation but, and shoot me down if I've got the wrong stick here, could you not employ a simple lever mechanism on the flipper/lift to give the desired speed/strength ratio instead of mesing with different gears motor side? It's a lot easier and cheaper to make some levers and pivots than it is to change gearbox ratios.
Hi Will, cheers. It's a fair idea to use some sort of leverage mechanism, but the problem is that I'm past that point. The whole design has been based around this linear actuator, and redesigning would be difficult and costly at this point, especially since I have basically all my parts ready. The other thing is that using a lever to increase the speed of the lifter would put extra force on the linac. Not only will a new motor increase the speed of the linac, it will also give increased torque (and thus force), so there doesn't have to be a tradeoff between the two. I've been looking into brushless motors with a similar diameter (and shaft diameter) to the current one today, if I could get sufficient speed and power from one of those then I'd just be able to straight-up replace the old brushed motor, no custom gearbox required. It's just a little difficult finding a brushless motor of the right dimensions that will run on a 5s lipo.
I re read your thread n I get now that it's speed your after not so much push.
Fair enough if you're that far down the line. I was suggesting not messing with the gearbox and just coupling the new motor directly to the one you have and using a lever linkage to get the speed right, much simpler if all you need is a 1:1 connection for the motor, could be done with a simple coupler.
Progress has been made! The linear actuator fiasco has finally been solved (or at least, most of it). I have upgraded the linac with a Leopard LBH3650 with a KV of 1185 (that's a measure of RPM per volt supplied in case anyone who doesn't know reads this - not kilovolts. I was originally going to get the original helical pinion off the old brushed motor and somehow 'cabbage' it onto the new motor's shaft, but it really didn't want to come off. I'm sort of glad too, because I think that would've been a lot more work. Instead, I removed the old motor AND another two gears in the train, because I'd ordered a mod 0.6, 25-tooth gear for testing anyway that happened to line up almost perfectly with the next gear in the chain and the shaft-hole. You can see what I mean in the pics linked below. All I had to do then was drill some new holes to match the motor's mounting holes, which are closer together than the old one's. I messed this up a bit the first time as you can see in the pictures, but it's not really a problem and when I basically drilled holes in-line with the existing ones, it just took a little bit of adjustment to get the gears to mesh. The result is a faster linac. Much faster than before, though I'm not sure about the power since I've dropped a part of the gearbox. However, I purposely ordered a higher-power, low KV motor, so it should hold up. Here's hoping it works when I test it in anger! Next step is to finish making the limit switches with the Arduino (which I think is mostly a matter of software) and then finally do a bit of metalworking to make the Hardox parts fit into the chassis.
Little imgur album of the linac images:
http://imgur.com/a/4VD9X
Test video:
https://youtu.be/W_P-0U14Q4U
Looking good, man! :) Glad to see you've managed to find a solution!
Thanks! I was pretty lucky the gear I bought was just the right size. :) It's definitely very gratifying now to see it running so fast after the speed it crawled at before.Quote:
Originally Posted by dotDominic
Good to know that most of those industrial standard thingies use Mod 0.6
One reason more to buy a set of gear-cutters of that size.
Yo yo yo, it's update time. I've been working hard, and I finally got the linac limit switches working. More to come, but for now I'll leave you with this video explaining how it works:
https://youtu.be/KXR07KbvTKc
Nicely done :)
Any worries about the brushless being too powerful for the actuator? Having destroyed a few of these that had the stock brushed motor replaced with an RS-550 one fitted without limit switches, and hearing how quickly the actuator nut moves from top to bottom in yours, that would be my concern, primarily either gears stripping or the plastic nut inside failing. They're of a pretty lightweight construction, even for feathers, though as long as it's not overstressed (i.e used as a crusher or a lifter trying to lift excessive weight) it should survive. Either way, good work and thanks for the info video.