Register To Comment
Page 5 of 7 FirstFirst ... 34567 LastLast
Results 41 to 50 of 63

Thread: Experience needed regarding FW Beater and Armor

  1. #41
    overkill's Avatar
    Member

    Status
    Offline
    Name
    Nick Martin
    Robots
    Mr Mangle - Australian 2015 Featherweight Champion 2016 UK Gladiator Shiny Scissorhands Decimator
    Location
    Sydney Australia
    Posts
    875
    Post Thanks / Like
    I could be cheeky and suggest this motor:





    It definitely has enough power and it is only 53mm without the shaft.

    Using a bar is fine, just try to get as much weight out at the tip as possible for more KE.

  2. #42
    Member

    Status
    Offline
    Name
    Jan
    Location
    Bad Oldesloe, Germany
    Posts
    94
    Post Thanks / Like
    thought so, but well, would be a shame if it was possible somehow (maybe by synching both motors or stuff like that), povide a somewhat "easy" solution and i won't use it just because i didn't think someone could find a way to make things work i can't. that would be stupid.

    Would it also be a problem if i would use two ESCs, two Motors, and one Pulley on either side?
    Just found out i'll get a space just big enough for the ESC right next to my weapon motor in the front part that's now angled. So won't be a problem to do this on both sides.

    While the NeuMotor looks great, it is specificated for much more than 5s, and honestly... getting my current motor/ESC-setup twice would be cheaper. But i bookmarked it, so it definitly is an option, and if not for this build maybe for a later one. Always could use flat, powerful motors, to find long ones is way less trouble.
    Also, with only 5S i don't know if the kv isn't too low on that one, would maybe even need a smaller pulley on the weapon than on the motor to get a good speed.


    Got on with the weapon design, did a spoked disc inspired a bit by Valkiri, i have to admit. Diameter 250mm, at 24mm thickness, with the outer ring as well as the spokes (four of them) being about 20mm wide (a bit more for the ring on the tooth and counterweight), coming in at about 3000g if made from Hardox.

    That's looking quiet doable, also having no problem to get it fit into the rest of the build. Motor and pulley on one side of the disc in this version, the axis will stay static and only disc/pulley on it will rotate (allowing some big bushings). Static axis is put between two 10mm Ali bulkheads, supported from the outer sides by 2cm HDPE coming at about 43-45° at it (have to fine-tune there a bit, depending on the actual motor i will use this angle will change a bit).
    Motor will also be mounted on the same bulkheads (on one side of them), the shaft going through the bulkhead and then the pulley on it. got about 3mm clearance between pulley and disc as well as pulley and bulkhead, just gonna need a longer weapon shaft, i fear. the original one is just 20mm long, and would only stick out 10mm from the bulkhead. not a good thing to mount a 14mm pulley on to, even less with the clearance. (and i'd have to figure out how to put the pulley on that, without making everything wider. maybe just put holes through the hole diameter of the pulley, make them threaded and bolt that thing on the flat part of the shaft.

    Would that be possible, or again put too much stress on the Motor?

  3. #43
    overkill's Avatar
    Member

    Status
    Offline
    Name
    Nick Martin
    Robots
    Mr Mangle - Australian 2015 Featherweight Champion 2016 UK Gladiator Shiny Scissorhands Decimator
    Location
    Sydney Australia
    Posts
    875
    Post Thanks / Like
    I was just joking about the Neu motor when I noticed that it fitted the space you had - its more at home in a heavyweight .

    Running two brushless motors on one shaft is fine, its just the ESCs that have to be separate for the reasons Mario mentioned.

    The disk design sounds fine, you could probably thin the spokes a bit as they are quite short, or even go down to three spokes to get more weight on the rim. If you can spin that up to a high RPM, it will be very effective.

    You can replace the shaft in an outrunner motor fairly easily. There is usually a circlip on the shaft at the bottom of the motor; popping this off with a small screwdriver lets you pull the entire endbell off the motor. The shaft is held in the endbell with two tiny grub screws. Loosen them with an allen key and then gently tap out the shaft with a punch and a hammer ( I usually end up using a long screw as a punch). Buy a length of silver steel the same diameter as the original shaft , cut it to length and do the reverse of the disassembly procedure. You are better of without the circlip groove in the new shaft, its a weak point where the shaft snaps.

    If you are mounting the motor on an aluminium bulkhead, there is a great opportunity to add a support bearing to the shaft. Here is a photo of a motor mount I made with an extra support bearing:



    The motor mounting holes limit the size of the bearing you can fit, but I discovered that a needle roller bearing is perfect for the job; it takes high side loads and has a small diameter. If that sounds useful, we can work out exactly what bearing to get.

  4. #44
    Member

    Status
    Offline
    Name
    Jan
    Location
    Bad Oldesloe, Germany
    Posts
    94
    Post Thanks / Like
    It indeed sounds useful, and i already had the idea of the extra bearing. just dropped it, because the original shaft of the motor is flatted at exactly that point, so a bearing there would possibly cause problems.
    But with a new shaft anyway, that's looking really good what you have there.

    What is the "flattest" way you know to mount a pulley onto said shaft?
    Was thinking about just thin holes from the outside through the complete radius, put a thread in, and bolt a... let's say M3 straight through that onto the shaft. Maybe two, one from each side, and flatten out the shaft there just a tiny bit or drill tiny crater (or what is a good word for it?) in it to give the screws something to hold onto.

    An additional hub would really widen the construction quiet a lot.
    I will try to get my drawings done the next 1-2 days and post them here, so it's easier to communicate everything (and maybe you'll spot something else i did wrong).

    Also need to think of a way to put the two pulleys and the disc onto a tube, without needed wielding (i just can't do it, and would prefer to make as much as possible on this bot myself and with tools and equipment so i can repair it myself if needed). Possibly screw the pulleys sideways in the disc (so better not thin out the spokes, at least not there^^), and do with those pulleys the same as with the small ones to connect them to a tube connecting them all. Only more sturdy, since there will be more energy involved.

  5. #45
    overkill's Avatar
    Member

    Status
    Offline
    Name
    Nick Martin
    Robots
    Mr Mangle - Australian 2015 Featherweight Champion 2016 UK Gladiator Shiny Scissorhands Decimator
    Location
    Sydney Australia
    Posts
    875
    Post Thanks / Like
    If you need to save space with pulley mounting, about the only possibility is grub screws at the bottom of the V. "Grub screws suck" is a bot building truism but sometimes there are no alternatives. You can improve their reliability by grinding flats on the shaft, using Loktite on the threads and using the largest possible grub screw. Drilling a recess for the point of the grub screw is another option but harder to do with a silver steel shaft.

    I am not sure about how your hub arrangement looks, but its really hard to put screw threads into Hardox. Its not totally impossible but will need a specialised tap, ultra-heavy cutting oil and a precisely sized hole. Most builders use an aluminium tube or block and tap into that. By coincidence Ellis just posted some inspiring examples:





    You probably won't need quite as many bolts as Ellis used

  6. #46
    Member

    Status
    Offline
    Name
    Jan
    Location
    Bad Oldesloe, Germany
    Posts
    94
    Post Thanks / Like
    New Pulsar looks so good...

    the design is now more or less inverted to what Ellis did.
    Disc in the middle, and an (aluminium?) pulley on each side of it, with a small distance (maybe just a washer, planning with 2mm here) between so the motor pulley will have some clearance to the disc, too.
    Now i'd put holes into the spokes of the disc, and put bolts from one pulley through the spokes of the disc into the other pulley.
    One of the reasons i want to go with four spokes, so i can use at least four (or maybe, depending on pulley size eight) bolts to hold everything together. Not the ten bolts Ellis used, but i'd hope enough. maybe i should put a smaller inner ring into that design of the disc, so i could bolt through that instead of just the spokes.

    Drilling recess points won't be that big of a problem for me, i'm a dental technician and used to work with small, but really hard stuff precisely. those are seldom round, but i think that should be achievable for me.

    But why is it that grub screws suck?
    hard to repair/get out once damaged? not strong/reliable enough?

    One more question:
    Why silver steel for the shaft? Does it have any special properties, or is it just the cheapest stuff you could use without problem?


    About mounting the motor:
    there are 4 screws M4 to hold the motor, distance from middle of one hole to the middle of the opposite hole 25mm.
    shaft is 6mm in the middle of those, but having this ringy thing at it right where it comes out of the motor.
    you said i could just not have the circlip on the new shaft, but wouldn't the endbell come off then? how would that hold? Just by the pulley not getting pulled through the bearing? That feels so wrong...
    Last edited by Runsler; 23rd February 2017 at 03:42.

  7. #47
    overkill's Avatar
    Member

    Status
    Offline
    Name
    Nick Martin
    Robots
    Mr Mangle - Australian 2015 Featherweight Champion 2016 UK Gladiator Shiny Scissorhands Decimator
    Location
    Sydney Australia
    Posts
    875
    Post Thanks / Like
    Silver steel is a generic name for tool steel that is usually hardened and precision ground. I can't buy it in Australia so I might have the details wrong. It will be much tougher than mild steel and a precise diameter.

    Almost all disks have a hub that the pulleys are bolted to rather than bolts through the spokes themselves. It doesn't have to be done like that but it helps with keeping everything aligned and strong.

  8. #48
    maddox10's Avatar
    Member

    Status
    Offline
    Posts
    2,294
    Post Thanks / Like
    Silver steel shafts are , in most cases, precision ground and polished, easy to harden steel.

    Not tool steel in itself, but used to make tools. It's "just" a good grade of steel. 2 kinds are common.
    1.1541 and the alloyed 1.2210

    This stuff is normaly sold unhardened.

    The other alternative is axle steel, as used for lineair guides. 1.7225, case hardened , precicion ground and polished.

  9. #49
    Member

    Status
    Offline
    Name
    Jan
    Location
    Bad Oldesloe, Germany
    Posts
    94
    Post Thanks / Like
    Only experimented with hardening a bit while smithing, and these experiments were... well, not quiet what we expected.

    But i guess it's way easier with just a short rod of steal than with those big chunks we used. (Might also help to watch a tutorial or anything before, and not just throwing hot metal into some cold water or oil^^).

    Will see what i can get here and what to do with it, but should be a smaller problem if at all.

    Also... i did some drawings.
    All as much to scale as i can do, and original size (didn't write all the numbers there, want to keep these sketches somewhat clean and only write the weight in the parts (didn't do all the math yet, hopefully get to finish that tomorrow).

    Also, the disc is a little bit smaller now, only 22,4mm ring with one about 1cm tooth and mass to counter that (drawing that by hand would have been awful, so just the ring to visualize the dimensions). So effectively 24,4mm weapon diameter. Had to reduce it a bit since i have miscalculated something, and either my wheels would have to stick out a bit too much (and be excellent spinner targets), or wouldn't touch the ground at all plus: gives me a more comfortable 5mm clearance to the "machine room" of the bot. also didn't draw the spokes to the inside, and an inner ring to get the pulleys bolted to. just seems to be fitting better here, since i have no ideas of hubs, too, and this seems pretty straight forward.
    Plus i was thinking of just letting the desc end at the inner ring and only connect it to the axle by the pulleys to get more weight from the mid to the outside. But i guess that would be way too much stress to those, even more if i want them to be just Ali.

    All in all: it includes more the idea of the disc than the actual disc, because i want to try and get most other things done before to calculate the weight as precise as possible and put as much as possible into the disc.
    Also doesn't include any wiring, bolts or the removable link yet, since i still ahve to figure out a few things about that. Mostly what screws/bolts and how many plus where it would be best to put the link.

    Mostly using HDPE in 20 or 10mm here for side Armor and some internal stuff, only the bulkheads where weapon and weapon motors as well as pulleys get mounted on are made from 10mm Ali.
    Top and bottom armour might have to be titanium to stay in weight limit (3mm), which is a bit weak for a wedgy thing. Not sure yet if i could possibly upgrade to 3,2mm Hardox, have to weit for how heavy the screws and bolts are and decide then. Could be i just use 3mm Ali first, just to see how it works, and upgrade later on. Will most likely just use ali for the front part, since i don't believe that would have to withstand much. Nothing inside there to keep save, even thought about just letting that part open. But looks do count, too, and it helps at least not to get grabbed or hooked in that easy. and possibly gives a bit sturdyness to sideway forces in the front. And i could put goggly eyes on that.
    As seen in side perspective, the wall between "drive unit" and "weapon part" is drawn in both parts, causing them to overlap a bit.


    Rest_k.jpgFront_k.jpgSeite_k.jpg


    Known possible issues:
    -Driving will be really hard. i expect a lot of gyro forces. Plus the wheels are almost completely concealed, so... only really slow turning once the weapon is powered up. And the wheels are far, far away from the center of gravity. At least in that direction this bot will be anything, but not pushy. on reverse (so wedge first) it might be different, if i can get under the other bot. with the enemys weight on the wheels, too it might work.
    -Due to those small wheels and a reduction of 28.4 to 1 on them, i will be very slow. So... doesn't matter gyros would make me turn slow, i am slow anyway. Not good considering the wedge, but anyway... if this actually is the biggest problem, i am happy. faster motors are one of the easiest things to change, but first need to learn how to drive at all.
    -Did a mistake on the brushed ESC: it fits perfectly in the space. But only without wires. So will have to carve out "canals" for the cables from the 10mm HDPE-wall next to the ESC. not a nice thing to do, but on the other side is just a weapon motor/esc, not the actual weapon. won't need the full 10mm there anyway.
    -The belts are longer than needed, so could be they might come off. but i got two of them, so it won't be as bad as for most other bots, and i'd rather have weapon motors and theirs ESCs a bit further in the back. both to save them from possible spinner-vs-spinner contacts as well as trying to get a bit more weight to the tires. If this is actually a problem, it won't be too big of a problem to move the motors further to the weapon and use shorter belts.
    -if i can't make the weight for 3.2mm hardox, top/bottom armor is rather weak, considering it is also a wedge. So... no wedge-first attacks vs. other spinners. Anyway, not that big problem vs. hammers/axes/crushers, since (except for the gearboxes) most internals got a bit of air between them and the top/bottom. you'd have to punch a rather deep hole before hitting anything important, hopefully that'll save me a few times.
    -still have to build an adapter to make the gearboxes connect to the top/bottom plates. If my current idea doesn't work i might have to turn the gearboxes 45°,too and bolt one side directly into the top plate, and put a small piece of HDPE at the bottom side so i can bolt gearbox and bottom into that thing. But this would make me build another way of fixing the battery/ESC, and not just shoving a sheet of 3mm lexan under the gearboxes and fix it to the wall on the other side.

    Well... still, i kinda like the design, and even have a nice paintjob in mind for it if i finish in time to do it.
    But would be great if you find any other possible flaws in this, i'd rather spend a few hours more thinking and drawing than wasting materials and ordering wrong things.

    Oh, and do you know a good way to bend 20mm hdpe to about 45°?
    would love to make the sides from one piece instead of bolting three together, but "just put it in the oven for how long and hot you feel is right and bend it" doesn't feel right.
    If i had to, i will use bolts there, too... but bending would look nicer, and save some weight on bolts again i'd rather use somewhere else.
    Last edited by Runsler; 23rd February 2017 at 20:04.

  10. #50
    Andy's Avatar
    Member

    Status
    Offline
    Name
    Andy Russell
    Robots
    Pendulum, Telekinesis, Push 'n' Shove, Ion
    Location
    Birmingham
    Posts
    256
    Post Thanks / Like
    I think driving will be a real issue, as there will be hardly any weight over the wheels, you might find the wheels just spin and the thing hardly moves, one thing I would say you could add to fix this but not change the overall design is using pulleys from the back wheels to another set, nearer the front, either side, so youll have three wheels each side powered by the one motor each side, this way itll drive far nicer, even though it adds a bit of extra complication, room and weight.

Register To Comment

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •