pack size is probably fine but with 5 motors in your setup you will probably need more then 30c rating
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pack size is probably fine but with 5 motors in your setup you will probably need more then 30c rating
http://www.hobbyking.co.uk/hobbyking...arehouse_.html
http://www.hobbyking.co.uk/hobbyking...arehouse_.html
these would deliver much more punch but the cost goes up
Ah, sorry, I completely forgot about C rating - not used to LiPos. Well, looking at HobbyKing, it seems the best solution is this: http://www.hobbyking.co.uk/hobbyking...dproduct=34854
with a 65C constant output.
-Edit- You sniped me. :P I'll get one of those.
Ok, almost everything's in place now. I'm aiming to get a final CAD diagram down by sometime this weekend. I do have a conundrum however: how do I mount the wheels? So I'm using 18v drill motors (should be simple enough). They have a 12mm outer (right handed) thread, which appears to be M9, and an inner left-handed M5 thread, and the screw protrudes by about 9mm when fully inserted. The screw head is 9mm in diameter. So basically my motor shaft has a 21mm (25mm at a push) length.
My wheels, however, which I suppose I could've been a little more selective with, are around 34mm width including the hub, with a 13mm diameter hole in the middle. The full wheel diameter is 100mm.
I thought about putting a coupling nut in the middle (I've seen a video where they heat them up and drive them into the centre of the wheel, melting the plastic around) but I can't for the life of me find an M9 coupler. I still have the chucks from all the drills, but they don't seem to look hackable enough after taking one apart today. I also thought about getting a new, longer screw and just clamping the wheel on with some washers, but M5 reverse-threaded bar or screws seem very rare, and even more so for locking nuts if I'm using bar. Is it worth getting new, thinner wheels (it would be a bit of a waste of these)?
TL;DR: My wheel holes are too wide and my motor shaft won't reach through, what do?
Thought you'd ordered a track setup...
The thread is 3/8" UNF.
The thread on the drill shaft is very unlikely to be M9; after M5, metric thread diameters are all even numbers. Almost all Chinese drill threads are good old imperial (also known as UNF) 3/8 - 24 threads, which should be fairly easy to find.
Well, I did, but it turned out the sprockets were nowhere near large enough for what I need. I'm gonna end up selling the Heng Long treads, but I'm still making tracks that will fit around the wheels, though the robot will run without them. You'll see when I make the final CAD. Sorry for the confusion.Quote:
Originally Posted by daveimi
Quote:
Originally Posted by harry hills
Thanks guys, I didn't realize imperial measured thread was that commonly used. Nice one.Quote:
Originally Posted by overkill
-EDIT- Ok, after a good amount of searching, (while I did find the nuts) it looks like it'll be cheaper and less bother to just get some better wheels that are thinner and have a hole I can just drill out to screw onto the shaft. I've found some, but I'm gonna make the CAD before I order them, just in case anything needs changing. I feel stupid that this is the third time I'm buying locomotion for this thing, but I guess I had to make at least some noob mistakes. The current wheels I bought were only £6 for all 4 anyway. They're gonna have to hang around until I figure out what to do with them. :P Next time, I'm making my own wheels, or following this guide if I have a drill press: http://www.windisch.co.uk/robots/archives/170
Alright, we're on CAD revision what, 50 now? xD Anyway, I spent a good amount of time on this one, so hopefully I've thought everything through. Everything I've modelled is either from measurements of components or material I'm going to cut to size and shape. I've got just about all of the electronics together now, and some of the other bits. The linac I'm using shouldn't be too hard to modify with the Turnigy SK3 brushless I've got, but I'll have to work out the exact placement for gears etc by eye when I get round to building it. For the lifting arm, I'm looking at getting some 10mm and 5mm steel pieces cut, which I can countersink, hacksaw or drill as needed. I'm planning for the scoop to be 4mm steel, but I really don't know if it'll be too heavy. Titanium's as possibility I guess, but I don't know if I can get a piece big enough, and I don't really want to go importing anything if I can help it. The linac can shift 300N as it is, so hopefully I'll have plenty of power and speed with the new motor. The scoop might need more than the four screws I've shown here. Also, I realize when fully extended, the linac motor hits the rear lifter axle, I might move the axle back a bit more to fix it, otherwise I'll just have to not push it back that far, or add some kind of limiter switch. The motor and the top of the lifter will have additional thin steel/HDPE armour too, but I'll look at just adding that on later.
The axles for the shovel mech are all 10mm diameter, and I'll be using nylock nuts and washers to keep everything nicely in place. The sides should be about 3mm steel too, but I think I'll go thicker if I've got the weight to play with. The rest will be 20mm HDPE (main frame) and 10mm HDPE (top and bottom). The top isn't really transparent, I just did that so the components are visible. On that note, as you can see, the LiPo is in one of the sides. It's about 500g, so I'm hoping it won't drag the centre of mass too far off, but I'll put something in the other side to compensate if it really becomes a problem. The side compartment was the only place it'd really sit comfortably, because I obviously want to get some foam padding in there too. You can see I'm sort of making the drive motor mounts integral to the chassis, which should hopefully screw together nicely with some barrel nuts. With regard to the wheels; they seem to fit well enough, and give enough clearance from the body to propel the robot without tracks, but I'm adding some tracks made out of some light bike chains I have with 3mm HDPE plates screwed on. The plates will have adhesive neoprene pads stuck on to give extra traction, and I might modify the wheels slightly to help them grip the tracks, but that remains to be seen, since the robot will run fine without them. You can see a breakdown of a section of track in the pictures, but I was too lazy to model it really intricately, much less bend it round the wheels in CAD. Long story short, the chains and screws will sit either side of the wheels, with the connecting plates contacting the outer face of the rubber tyres.
One thing I'm still a little unsure about is how easily the side armour will get chewed off by horizontal spinners. I can't support it through the wheel hubs because the screws won't reach, so it's just attached by two big HDPE blocks in the middle. Should I aim to make it thicker, or try and curve it back round to screw onto the front and back of the body? This'd be tricky with the tracks, but if it's necessary, I should be able to find a way to do it. Anyway, I'll be setting up the electronics tomorrow, getting all the connectors soldered on and testing everything, etc, so at least I'm making some progress. :P
FRONT:
http://i.imgur.com/4tbv2U1.jpg
BACK:
http://i.imgur.com/iLhKPgS.jpg
TOP:
http://i.imgur.com/x25VPps.jpg
SIDE:
http://i.imgur.com/DtiygNd.jpg
ISOMETRIC-ISH VIEW:
http://i.imgur.com/TgAgTSn.jpg
I would definitely try to attach the side armour at the back & front - it will get damaged or ripped off if it is just attached with four screws in the middle. The rest of the CAD design look great.
Thanks. :D Yeah I'll try and bend the armour round the front of the tracks there. Should be possible.Quote:
Originally Posted by overkill
Just a thought - if you add an extension to those plastic spacers between the wheels, it will help to keep the treads on and improve grip.
I actually have some little 40mm castors which I might add to help track tension. They should hopefully offer lower rolling resistance.
Just changed the shape of the steel lifter mounting bracket (shown on its own in the top right) to move the lifter axle well clear of the brushless motor at full extension. Should be fine now.
http://i.imgur.com/hetwxg1.jpg
Moving the pivot pion that far back makes it vulnerable to vertical disk spinners - it might be safer to limit the movement of the arm.
How about moving it forward again slightly? How close to the edge is too close? That bracket should be 5mm steel btw.Quote:
Originally Posted by overkill
Most vertical spinner disks are 16" or less in diameter, so draw a circle that diameter in your CAD and see if it touches any lifter parts before it touches the armour - it could be that you don't have to move anything.
Ok, sorry though, what are the " marks for? Surely you don't mean 16 inches.
I think the largest vertical disk I ever saw was about 16 inches in diameter. Nowadays builders are using smaller, thicker disks so if a 16" disk misses you lifter, you will be safe from the smaller ones too - its always good to plan for the worst case scenario.
I've moved the axle 7mm back in, and a 16" circle just hits the protruding lifter arms before hitting the edge of the armour. Can't really hit the main axle though. I might just end up armouring the back end a little more if I can't get the mech any closer in. I don't want to have to mess about with the limiter switches inside the barrel of the linac.
That sounds like a good compromise - altering the limit switches would be a major PITA.
Thanks so much for all your advice by the way, I have a feeling it'll really pay off having asked these questions down the line. I really appreciate your patience answering my noob questions. :P
I have an ulterior motive - having just ordered almost the same linac as you, I get to see how your design pans out before I have to get mine built :). I'm also interested to see how your tracks work out.
Me too. :D
Alrighty, so I got around to starting on my electronics today (waiting for armour and other bits to arrive before I can start on the body). One thing I've learned is that EC3 connectors are the bane of my existence, it took me a good two hours to figure them out and get a few of them soldered. Before I start modifying TZ85s into brushed variants, I decided to test my third TZ85 (which will stay brushless) with my Turnigy Helidrive SK3 Motor. It works great on the throttle slot. However, it only spins one way. I've tried connecting it to other receiver slots, and the receiver refuses to start and just beeps if I don't hold the stick down at 0.
So this is a problem: I need to get my motor to be stationary when the stick is in the middle, turn one way when it's at the bottom, and the other when it's at the top. I think this is an ESC issue, having poked around on various RC forums to try and get the transmitter to tell the receiver to run backwards. Now I'm sure it'll be fine on the brushed modified TZ85s given that they've been set up especially for this situation, but what do I do with this one? Do I look for some other brushless ESC whose zero point is at 50% throttle? Or is there some way to modify a brushless TZ85 to run forwards and backwards?
Anyway, here's a quick vid of me testing the SK3, sadly with no sound because I forgot to unmute my mic. :/ Next time I'll remember. :P
https://www.youtube.com/watch?v=D88F...ature=youtu.be
Ok, some research later, it would appear that TZ85s are unidirectional ESCs. I didn't realize some ESCs were only one-way. Obviously they have been made reversible by the BotBitz hack, but that's for brushed motors. Does anyone know how to program them to be reversible, or could you suggest an appropriate reversible brushless ESC for the motor if this isn't possible? Would something like this be appropriate?: http://www.ebay.co.uk/itm/EZRUN-120A...IAAOSwwPhWil9e
You can get a new firmware for the TZ85a that makes it reversible with a brushless motor. Search for 'SimonK tz85a reverse' but be careful, there several versions with different functions.
Ah yeah, thanks! I've found a big zip file with hex files for loads of different ESCs. Looking at the list though (cross-referencing with the github page), there doesn't seem to be one for the TZ85. Although, there are a few videos of people who have done it.
-Edit- Never mind! According to shakrenaaj (Shakey, I think)'s youtube, it's the BlueSeries version I need.
-Edit 2- Yep! It works! So for anyone who comes across this thread later, here's how you change a brushless TZ85A ESC from unidirectional to bi-directional (reversible), so you don't have to wade through the internet maze I did:
-Get the KKMulticopter Flash Tool from here.
You can use some other flashing tool if you want, like Atmel Studio, but I found this easier.
-Open up your TZ85 to reveal the board inside (you may need to 'convert' some of the 2mm-headed hex screws like I did with a junior hacksaw. Two of them went bald on top straight away, so I had to make a groove in which I could use my small flat-bladed screwdriver.
-Make sure you have the USBasp programming device, and either solder on programming wires (as in the brushed hack post) or use a socket flashing tool like I did. Also make sure you have your USBasp drivers installed (you may need to turn off driver signature verification on Windows).
-Download the SimonK hex files from here. For the TZ85, you'll be wanting the 'bs.hex' (BlueSeries) hex file. Just put it somewhere where you can get to it in a second. There's more information about the hex files in the README file in that Github directory.
-Open up your KKMulticopter Flash Tool (use the 64-bit or 32-bit exe, whichever's appropriate for your system). Make sure the options are set as in the image below. Basically though, just make sure the USBasp device is selected (make sure you've got it plugged in too) and click on the 'File' tab as seen below. You'll need to click the floppy disk button to browse for your bs.hex file now.
-Now just hold your flashing tool (if you're using it) onto the ESC's chip with the red dot on the tool aligned with the small dot on the chip, and click the green flash button. Provided you've got the drivers installed and everything's done right, the software should print out that it flashed successfully. Then just reassemble your ESC, and you're ready to go! Once you hook your receiver, motor and battery back up, the motor should run forwards or backwards, depending on which way you push the stick.
http://i.imgur.com/Be5KjkU.png
Thanks again for your help, overkill. This weapon is gonna be good.
excellent info on here for the hack on the tz85's
will that bs.hex also work for the hack to brushed ?
I'm pretty sure it won't, but all you need to do to hack for brushed is follow this same method with the hex file from the brushed hack post I linked up there. You'll probably want to check out the videos on that post too, as they show a similar process. But yeah, if you follow these instructions but with the hex file from there, you should get forwards and reverse brushed ESCs. :) I'll be doing it today.Quote:
Originally Posted by cnc_machinist_andy
Oki doki let me know what mods u do to urs and what the hex file is :)
Edit1 those are the videos i seen but im guessing you only need to solder the join across the switch at the end.
Oh and snip off the 3rd motor wire if u flash the chip using the piggy back connector?
Yeah, if you're using the connector, you don't really need to modify any hardware - you can bridge the switch for convenience and robustness, and snip off the third wire if you want, but I'd only do that when you've checked everything's working. Now I still haven't done the brushed hack yet, but this is the hex file I'll be using. I'll tell you how it turns out.
Brushless hack worked like a charm! Many thanks to the guys at BotBitz for making the software available, and Danjr1 for modifying it for use with the DX6i's mixing.
https://www.youtube.com/watch?v=7Mqvagi-mms&feature=youtu.be
Looking good. Quick question. Thats for the dx6i control. Is there a library for controllers?
Depends on brand and even on reciever .
It's all about the data transfer from the reciever to the servo or ESC.
Spectrum is known for the small width of the signal used.
Electronics are almost done, finally received all my HDPE, and got me a jigsaw today. I've read up a bit on cutting HDPE, and apparently it's best to spray it with water as you're cutting, to stop it melting. Does anyone have any other tips or suggestions on cutting 20mm HDPE before I start?
we cut hdpe on machines using high speed steel cutters and also carbide cutters so we just blitz it, but i reckon that you should go with a coarse blade run slow rather than a fine blade run fast. dont let the blade dwell too long on the cut or it will heat up and blunt too quickly.
as for water, be wary when using electric tools ....
i'm sure others who've manually worked hdpe will chip in also :)
Yeah, I had a quick go just now at cutting one of the side panels (I have more HDPE than I need thanks to the standard sizes sold) and I didn't really see any sign of melting. I'll have to practice at cutting straighter, but I don't think I need the water here.
If you use any kind of coolant/cutting oil for HDPE, life will be easier.
It's only annoying if you want to weld it after the cutting. Then you'll have to get rid of any residue. Aceton is one of the better cleaners for this purpose.
I successfully cut 20mm HDPE with a standard coarse wood cutting blade in my circular saw
Just be wary of HDPE swarf - gets everywhere