15'000 RPM!!! That is completely insane :o How on earth will you combat that gyroscopic forces? I just cant see you you will keep it on the ground... super-strong neodymium magnets?
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15'000 RPM!!! That is completely insane :o How on earth will you combat that gyroscopic forces? I just cant see you you will keep it on the ground... super-strong neodymium magnets?
Just makes it more of a challenge to drive... Can't be any worse then 360 to control
that drum looks slick, what's the diameter? also are you not worried about engagement issues at such high rpm?
brushless inrunner.... intresting.
Good point :)Quote:
Originally Posted by mr_turbulence
Jonny - 95mm OD, don't really know about engagement.... Might be a bit crap.. But when it does grip it should be pretty impressive...
No idea on the KE it will deliver, but from what Gary has told me... It'll make bonner look like a toy :P
And yeah... In runner... Castle creations neu 2200kv... I used to be the only person using scorpion motors... Now everyone has them... So thought I'd try something else.
what kind of reduction are you running, you dont need as big a reduction with say a 120mm a drum as you do with 200mm disc? If they weigh the same... ummm I dont know...
Thats right yeah... using a scorpion hk4025 890kv on 6s in 540 proved that... the beater on that was close to 2kg and it span up to 8000rpm in 1 second on 2.5:1 and pulled like 40a....
Gone for around 2.9:1 in this one, with a higher KV (2200) depending on how charged the lipo is i guess it'll spin upto 14-15k in 3 seconds ish.
Drums and beaters are able to spin up far quicker simply because they have a lower moment of intertia (essentially more of the mass is closer to the center of rotation than a comparible weighted disc). This has advantages and disadvantages. Advantage is that it spins up quicker however you have to spin it to a higher speed to get the same kinetic energy as a comparible weighted disc.
Spinning at such a high RPM will be an interesting experiment certainly but you will have to be careful that bearings etc are rated for such speeds and whilst it won't be an issue for you Dave, the machining has to be top notch as any misalignment or friction in the system will cause a spectacular premature failure.
Yeah, we are going to have to be extremely careful that everything lines up properly!
What is the difference between the HK-40's and the HK-50's? [Besides 200g and $150!] I am guessing the 50's provide more torque but I know that you cant give a maximum torque for a brushless motor as the torque drops the faster it spin's.
Or could you drop to a 1100kV HK 30 to save some money and still be able to make an effective weapon out of it?
your going to have to be careful with your design.... my bulkheads are 20mm Alumec89, there not going anywhere :P Also the bearings im using are taper bearings rated to 18,000rpm...not cheapo ones.
With all scorpions the numbers dirrectly after the letters corrispond to the motors diamater... also... the bigger the motor, the more power it has generally... the data sheets for the motors are on the scorpion power site.
Sorry, forgive me for being thick but where are the data sheets on the website, I can only find the dimensions at the bottom of each motor page, and there doesn't seem to be anything in downloads
http://www.scorpionsystem.com/catalog/m ... 890-12N8P/
scroll down..same for all there motors...all the info you should need.
So there is no start up torque figures or acceleration graphs? We just have to guess our pulley ratios and disc/drum weights... I thought it would be more accurate than that but its obviously worked for everyone else.
Are these suitable bearings for the drum? http://uk.rs-online.com/web/p/roller-bearings/0514120/
And these as part of the tensioning system? http://uk.rs-online.com/web/p/roller-bearings/0513868/
I am looking at their oiled speeds and their dynamic loading numbers
edit: sorry for all the questions
There ok, but a 12mm shaft is a bit small...id go for 17mm minimum..
im using these (RS Number 506-236) as i wanted something to take exstreme loading- for instance if NST hits it side on....verticles are weak to a good horizontal, with one hit on 360 i hit a verticle once, ruined his 10mm solid aluminium bulkheads and bent his 12mm thick hardox disc, bent the axle and smashed his disc motor...totaled his disc setup due to the weakness in his bulkheads....which apeared strong enough.
Because of this ive gone for a small diamater (less leverage to smash the bearings/bulkheads) a thick shaft (20mm solid stainless) and beefy bulkheads (20mm solid alumec) my bearings will be compressed up to the bulkheads, so the drum and bearings will be a perfect fit in the chassis....
If you plan on using that honey comb ali for your bulkheads id strongly reccomend otherwise.
Will and jamie seem to do well with HDPE bulkheads as they flex quite well.
We were going to double it up to 26mm thick with 2mm ti on the outside, and then glue in an Alu insert to sit the bearing in but your method will be much more reliable. We might test the cellite bulkheads in a drum beetle but we are now going to go with the tried and tested methods
eugh, i typed out a long post about aluminium honeycomb but my net screwed up when i submitted it. Can't be bothered typing it all again. To summarise, it can't be used to directly insert bearings into however is very usable. If you want info on the best ways to use it, give me a shout.
Ed's done a great job of cncing my bulkheads so far at work;
Skimming down the alumec 89 to exactly 20mm;
http://i685.photobucket.com/albums/v...s/a4cd5731.jpg
bulkheads and back bolted up;
http://i685.photobucket.com/albums/v...s/d836dc90.jpg
Just needs a square hole in each for the motor gearbox to sit in, 2 slots in each and a pocket for the drum axle to sit in, then there done... might make up the devider plates in the chassis this week some time.
Aww Dave, you should've told me you were gonna rebuild Drumroll in ali for me :wink:
Just kidding, it's looking great. I'm really liking the increase in drumbot production at the moment, gives me motivation to keep Drumroll running well and improving any areas that need it.
In-runners seem to be popular with the US drumbots and worked well in Galactus so I'm sure it'll pack a punch. Timing pulley looks weird without the teeth but hey, it works... :)
Does the toothless timing pulley mean the belt can slip in impacts? Why not use a v belt or o belt if you want it to slip?
V belts dont like tight radius's such as the small pulley id want to use on the motor, and i dont trust the o belts to remain at a constant tension.
Timming belts (especially the HDT range) are very strong and flexible...
Jamie- yeah i know it looks like the love child of galactus /touro / drumroll but its kinda hard to make a drum robot that doesnt look like that while being invertible :P
Whats the length, diameter, weight and speed of drumrolls drum? Trying to work out if im going to actually be able to turn without flipping it lol.
It's gonna flip. Get some magnets in there
Yeah, trying to come up with something different looking is tricky. Mine is pretty much a Proteus/Reboot love child, figured the best way to make it look different was to lather it in metallic blue paint.Quote:
Originally Posted by mr_turbulence
Can't remember the exact stats off the top of my head but it's something like 180mm long, 76mm diameter tube (with 12mm deep teeth) and around 2.2kg spinning at - theoretically - 7000rpm, so minus a few hundred for losses.
To be honest, I find the gyro-dancing reasonably controllable. If I'm going in a straight line then turn, one side will lift up but it drops back down again by the time you've completed the turn. Actually helps to prevent over-steering to a degree. If I want to use the gyro to flip it, I usually have to crank the transmitter stick completely to the left or right to get it to turn itself over. So it may look wild and out-of-control, but I like to think I've got it obeying my commands :lol:
If your drum is heavier/faster I imagine the effects will be exacerbated, so you may well feel the need to add magnets. Best bet would be to just try it out once it's all running and see what you think.
Just think of it as a self righter for free!
Changed my mind on the gear ratio, decided to slow it down to 13,000rpm on paper due to strain on the motor etc... glad i did, as i tested it today and its a tad current hungry on spin up.... works ok though;
http://www.youtube.com/watch?v=F9EEOcTAvKA
http://i685.photobucket.com/albums/v...20drumtest.jpg
should be able to get the current draw down, belts slightly tight at the moment, and the timing on the motor wasnt set right.
Jesus Christ that's insane man, the noise! The RPM! The amps?!
Combat robot porn. :lol:
Scary sounding stuff. Will be interesting to see how effective it is at such high speed
I really appreciated the perfect spin up no wobble / vibration.
Yeah seems ok gabe, it was clamped in the vice for the test, but it would of shook the table a bit if it was out of balance... I'll try get the top and bottom wedge/feet bits made in the next few days so I can do a spin up and drive test.
I can't wait to see it drive, just to check out how the drum effects it. I must say that it's beautiful in its simplistic form. Will you be leaving the wheels unprotected? Could you give us some dimensions
280a!!!
What battery are you using? How do you fuse for that!?
Wheels will be protected, will have a Hardox ring around it when finnished.
Pj- I have a 100a auto fuse inline with the lipo, to blow that it'd prob take around 250a for 4 seconds at a guess... My lipo is a 5000mah thunder power 45/90c 5s... Meaning it can handle 225a continuous current draw, and upto 450a burst :)
Once I've sorted out the belt tension and changed the frequency the motor runs at in the software I should be able to get the spin up current below the 250a mark at a guess. Sounds a lot, but that's me hammering the throttle for a fast spin up.... Could possibly get it below 200a if I wanted.
Thats better;
http://i685.photobucket.com/albums/v...720spinup2.jpg
spins up to 12,912 RPM and draws 216amp.... was taking it a bit easier on the throttle... but i think the spin up is good enough now.
Think its the fastest spinning weapon on a featherweight in the UK so far now :).. if anyone knows the weight/OD/RPM Of touro feather in the US id like to know... as thats the kinda effect i was aiming for.
Only 12,912 rpm?!.......
What weight and OD are you running?
the drums 3kg, 95OD x 220mm wide
That's going to pack a serious punch!
If it can engage anything...Quote:
Originally Posted by PJ-27
I mean no disrespect to Dave at all by that remark (he can build darn better machines than me :)) but those teeth look far too small to make any meaningful engagement on another robot. I could well be wrong, but it just appears that way.
Oh yeh, at that RPM there will be lots of grinding (I don't think size of teeth matters much at this sort of speed) and that much kinetic force it'll be a pain to drive, but when it does engage!
I dunno, I reckon the depth of those teeth will be fine. We'd naturally assume that the bigger the teeth, the better the engagement. But to compare, Drumroll II has quite big teeth and Galactus/Touro Feather have quite shallow teeth (like Dave's machine). I can get some good hits with mine, but Galactus was getting fantastic hits too, and if you check out some of the Touro vids, their opponents are getting serious airtime!
The top-end rpm might be a bit high but it's easy enough to drop that down if necessary. Either way, it's gonna hit hard.