Team Pasty Build Diary: Loki

Hi Guys, pretty new here so this is my first post. I've started building a featherweight which I am naming Loki (hopefully it's not taken!). It's going to have electric lifting forks, inspired by Panic Attack and Biohazard. At the moment I have an MDF mock up of the chassis and the following components:

2x drill motors
2x BotBitz 85A ESCs
1x Orange 6CH RX
1x Spektrum DX5E TX
2x 75mm RobotChallenege Blue Wheels
2x 7.2V 3300 mAh NiMH batteries in parrallel (borrowed from my Battle Rat, Nasty Pasty)

The final chassis will be made from HDPE and hopefully if I can get enough cheap off cuts the armour will be titanium. I have a few new bits and bobs coming next week, a Turingy V-Tail Mixer (controlling is interesting at the moment!) and 2x 9.6V 3300 mAh NiMH batteries and an electric actuator.

Would appreciate feedback/tips/advice :)

Here's some photos of progress so far:
[attachment=1:kf34ow3k]2013-02-22 22.06.41.jpg[/attachment:kf34ow3k]
[attachment=0:kf34ow3k]2013-03-03 15.29.39.jpg[/attachment:kf34ow3k]
And a video:
https://www.youtube.com/watch?v=FdrcsAzbNHA

Cool design, what controllers are they?

^They're the 85a Botbitz speed controller. It's a reprogrammed and electronically tweaked brushless motor controller. Here's their site: http://www.botbitz.com/

As I have said, your machine is looking very nice thus far, Chris! You're going to be amazed when you up your batteries to the 9.6v in series, the machine will be over twice as fast as it is now. :lol:

Will it be a four-bar lifter like Biohazard or fork lifter like Panic Attack?
Doesn't the Spektrum DX5E have built-in mixing?
How will you control the lifter? Another BotBitz 85A ESC or using an H-Bridge?

I know it's just a mock-up buy, when you get the actuator, make the robot as compact as possible, you will save lots of weight and money in materials.

Looking good.

http://www.spektrumrc.com/ProdInfo/File ... Manual.pdf

Go to page 11 on the PDF. Look at ELEVON/DELTA mixing. This will allow you to mix the signals at the transmitter without the need for a separate one in the robot.

You may have to swap cables going into your receiver around or reverse a channel but it will work with the right combination!

Quote:

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Originally Posted by Merkabah_PT

Will it be a four-bar lifter like Biohazard or fork lifter like Panic Attack?
Doesn't the Spektrum DX5E have built-in mixing?
How will you control the lifter? Another BotBitz 85A ESC or using an H-Bridge?

I know it's just a mock-up buy, when you get the actuator, make the robot as compact as possible, you will save lots of weight and money in materials.

Looking good.

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It will be a four bar lifter with forks, at least that's what I'm aiming for.

I tried to find out about the mixing, from what I've read it doesn't but I could be wrong. I'm all new to this lol

Yeah I've made an H-bridge to control the lifter, tried to upload a picture but it only let me do 2 for some reason?


And thanks I'll keep compactness in mind :)

Quote:

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Originally Posted by Ellis

You're going to be amazed when you up your batteries to the 9.6v in series, the machine will be over twice as fast as it is now. :lol:

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Looking forward to it :D

Eventorizon posted the manual for you TX, take a look at it.

It took me about 1hour to be able to connect my TX to the computer and make the mixing work. Trial and error.
My TX alows me to connect it to the computer while i operate the robot, so i could test every change as i made them.

[quote=Eventorizon]http://www.spektrumrc.com/ProdInfo/F...r /> <br /> Go

Reversing the channel should do exacly the same thing as reversing the motor wires, but if ch.rev. isn't working you can do that.
I don't know how to mixing is done on your TX, but in mine i have to assign 3 pairs of master/slave channels and say their percentages, like:

Master: ch1 %:100
Slave: ch2 %:-100

I had to mess around with rev. and +/-% to get it right.

Try to reverse the motor wires, if that does the trick, you are all done.

Looks very nice for a wood bot.
Forget the ti stick with MDF :rofl:

Quote:

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Originally Posted by Merkabah_PT

Reversing the channel should do exacly the same thing as reversing the motor wires, but if ch.rev. isn't working you can do that.
I don't know how to mixing is done on your TX, but in mine i have to assign 3 pairs of master/slave channels and say their percentages, like:

Master: ch1 %:100
Slave: ch2 %:-100

I had to mess around with rev. and +/-% to get it right.

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I don't think the DX5E can do that :? Mine just has switches for mix on/off and then you can reverse the channels

Maybe you can find some info on these links:

http://www.rcpowers.com/community/th...bilities.9387/
http://www.youtube.com/watch?v=rmdst80KZd4
http://www.rcgroups.com/forums/showthread.php?t=943411
http://www.rcgroups.com/forums/showthread.php?t=1273639


From what i read on the third link, there is a known problem while using the mixing and reversing, when you reverse on channel, the TX automatically reverses both.

Hope you can find a solution.

If I remember rightly (and I may not since I don't own a DX5e), the built-in mixing on the DX5e limits the elevator channel to around 60% so your robot will seem unusually slow when going forward and back, but will turn left and right at the correct speed. It's not something that's adjustable as far as I'm aware so your best bet would be to leave it turned off and use an external mixer if you want single stick driving. Although watch what external mixer you buy as some of them also have fwd/bck limits.

The DX5E has half throws on all mixed channels I find. Get a GWS mixer, they don't limit and don't mess up your failsafing like the other cheap ones.

Sometimes you do just need to switch the wires on the motor, swapping functions on the Tx will only get you so far and the DX5E is pretty limited.

Thanks for all the info regarding mixing on the DX5E. It would appear that this model has a fault so can't use the in built mixing, bummer.

Received the new batteries today so got them all in nicely and now the robot really goes!

Also inserted a removable link, made the front of the chassis angled and gave it some aluminium armour.
[attachment=1:3oj6tw6o]2013-03-06 15.14.31.jpg[/attachment:3oj6tw6o]
[attachment=0:3oj6tw6o]2013-03-06 15.15.16.jpg[/attachment:3oj6tw6o]


Am having some problems though. When on it will intermittently move on it's own, and it seems like sometimes the wheels keep going for a tiny bit after letting go of the stick.

Could the problem be down to the cheap mixer? I checked the failsafing after what PJ-27 said and it has messed it up.

I took it outside for a test run and managed to drive it into the curb and bend a corner of the aluminium so one of the wheels was off the ground :lol:

Could someone tell me where I would wire in a power LED?


Cheers guys

Try to remove the mixer, if the problem dissapers, blame the cheap mixer.

The easiest way to add a power on led is by connecting it to one of the channels on the RX, but you will need to use a resistor too. Use this calculator to find what resistor you need. http://www.hebeiltd.com.cn/?p=zz.led...tor.calculator

Are you using the two red wires from the ESC's? If you are, remove one from the RX connector and use thermal tubing or electric tape to keep it from causing short-circuits.

BTW, way waste alu making armor to a mockup? :?

Removed the mixer and yea seems to have irradicated the problems I was having, ordered a GWS mixer now.

Good idea for the LED, I have a 12 V LED so thinking the resistor won't be necessary?


Yes I was using both the red wires from the ESCs so have removed one of them.

Couple reasons why I wanted to make armour for the mock up, 1) cos I have some spare ally, 2) it'll help visualise the real armour and how it will all fit together etc, and 3) cos I thought it would look cool :D

Also I'm considering entering it into the arena at Portsmouth to get experience driving it in the context of a battle. Even if the MDF doesn't survive :lol:

Thanks for the help :)

Quote:

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Originally Posted by Merkabah_PT

Try to remove the mixer, if the problem dissapers, blame the cheap mixer.

The easiest way to add a power on led is by connecting it to one of the channels on the RX, but you will need to use a resistor too. Use this calculator to find what resistor you need. http://www.hebeiltd.com.cn/?p=zz.led...tor.calculator

Are you using the two red wires from the ESC's? If you are, remove one from the RX connector and use thermal tubing or electric tape to keep it from causing short-circuits.

BTW, way waste alu making armor to a mockup? :?

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I am sure you can find some one to make a couple of whiteboard fights, against a wedge/rammer or some one with the weapon turned of.

The RX only outputs 5v, so a 12v led will not glow very brightly. Get a couple of regular high brightness 5v leds, or power your 12v one from the main baterry. The resistor you will need will depend on how many volts your battery outputs.

Weekend update:

New GWS V-tail mixer came and works brilliantly so mixing is sorted

Cut a piece of aluminium for the top

Added an power on LED, 5V powered from the receiver (thanks for the advice Hugo!)

And that's pretty much it

Here's some pictures:
http://i1298.photobucket.com/albums/...ps657c3161.jpg
http://i1298.photobucket.com/albums/...psb9f9742f.jpg

And a video
http://youtu.be/gUAMYU9jPw8

It's a bit slidey cos the floor's still covered in bits of ally, and the motors still need lowering a bit to increase the ground clearance (keeps getting beached on the door mat!)

Looking forward to Portsmouth!

Those are some very neat straight cuts on the Ali you've got there, what did you use?

I'd be careful putting the LED on the Rx, you don't want to take power away from it since it's your only form of communication with the robot.

Most people put their LED in parallel with the main power block of the robot. Also different colour LEDs have set voltages, a 12v LED is just one with a resistor already built in.

Ha thanks, I think the photos do it more justice that it deserves. I used a jigsaw so they're not perfectly straight but I guess I didn't do a bad job lol

I'll see how things go in Portsmouth with the LED and make changes if necessary. Thanks for the heads up :)

Haven't finished stage 1 of my robot yet but have already been designing stage 2: the four bar lifter!

http://i1298.photobucket.com/albums/...ps20d2e69b.jpg
http://i1298.photobucket.com/albums/...ps1ed7558d.jpg
http://i1298.photobucket.com/albums/...psea4e0221.jpg

The final version won't be as wide and made of something a bit stronger than cardboard, pencils and sticky tape!

Are you gonna build the lifter on top of the robot or inside?
You have more that enough space inside of it. Try to make the robot as small as possible.

Normally I would agree, but I have to say it looks pretty cool sitting on top like that. Gives it a weird sort of forklift/telehandler look, quite industrial feeling. Should be good to see it progress :)

Yea it will be inside, once my dissertation and exams are out the way I'll get it all sorted. First stage is to get something that moves and can enter the arena, and I'm almost there!

Quote:

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Originally Posted by RogueTwoRobots

Normally I would agree, but I have to say it looks pretty cool sitting on top like that. Gives it a weird sort of forklift/telehandler look, quite industrial feeling. Should be good to see it progress :)

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Thanks Jamie :D

Really nice machine, look forward to seeing it running.

Well I had my first experience as a roboteer in Portsmouth over the weekend. I made it to all 6 featherweight fights, and Loki was still running at the end so am pleased with that. The MDF stood up to the other robots more than I thought it would.

First fight: flipped over and then flipped out by Heatwave (I think!?)

Second: Lasted longer than last time but managed to drive in under the arena flipper running away from Explosion.

Third fight: Thrown across the arena by Explosion and it died. Got it back to the bench and opened it up and turned out my batteries were missing! Them falling out also pulled one of the wires off of the link so had to solder it back on frantically.

Fourth fight: Didn't replace the back panel and after entering the arena and doing a spin the wire came of of the link again and it died. Then Explosion got a couple flips on me and ripped me apart. Very frantically put it back together, soldered the link better and ran out to Homebase to get some new cable ties to keep the battery in place

Fifth fight: The best of the event, had a few pushes with Small Cheese and Full English but was then flipped over by someone, then pushed onto the arena flipper and then finally pitted but was still running at the end of it.

Sixth battle: Drove in okay but then died pretty much straight away. Turned out the link 'socket' melted a bit when we were soldering and the link wouldn't fit in completely and it fell out after a collision. Once the link was put in it worked fine so happy with things :)

Met some nice people and had a great experience. Next stage will be to finish my dissertation (!) and then make the weapon out of MDF to see how it will fit in etc so looking forward to that.

Here's before Portsmouth:
http://i1298.photobucket.com/albums/...ps1d314d59.jpg

And after...
http://i1298.photobucket.com/albums/...psf82b3e05.jpg

Well it's been a long time since I've updated this but I have now finished uni so have a lot more time but little money so progress has been slow. My dad has kindly donated some timber so have been able to upgrade and modify the original chassis to incorporate the 4 bar lifter and mount all the gubbins in properly.

Still need to save up for the ally box section for the main arm and the other 2 bars but so far so good! The arms are made of 1" x 1/4" ally flat bar and attached by M8 bolts.

Here's how it currently looks:

http://i1298.photobucket.com/albums/...psa56eac9d.jpg

Very happy with it so far, unfortunately can't make it to Guildford but it won't be ready in time anyway.

As always I welcome people's feedback and suggestions :)

I like it :) Cool lifter. Can't help thinking that its not going to drive particularly well with the wheels that far front. maybe look into 4wd for the future?

Thanks Harry :) 4WD is definitely a consideration for the future, I'll see how I'm looking for weight when I finish my current design.

Liking the design, looks like an industrial vehicle like a fork lift or something. :)

I have three ideas for the lifting part of my four bar mechanism and was after some opinions/feedback/improvements. Sorry for my limited CAD skills lol

First and original idea, long forks. Originally I wanted to be able to pick up and drive around with other robots but watching videos of robots since then it seems that it would more than likely tip forward like Big Nipper does. I've tried making it as wide as possible/sensible and placing the heavy parts toward the back of the robot but until I can make the arm it's all just guess work whether it will work. I also thought that if they were long they might have a greater reach than a spinning weapon would so would be able to turn over a spinner before the disc got close enough. I am concerned that they would get bent though.

http://i1298.photobucket.com/albums/...psc8c345f1.png

Second idea is to have the forks but to have them shorter so they'd be less likely to bend but wouldn't have the reach advantage of the longer ones.

http://i1298.photobucket.com/albums/...pscf5cb4ce.png

Last idea is the more standard Biohazard/Storm 2 type end which would propably be stronger and easier to make but doesn't look quite as cool as the forks.

http://i1298.photobucket.com/albums/...ps32300537.png

What do you guys think?

I don't know enough to say which would really be best, but you seem to think the last design is probably most practical?

I think winning, looks cool.

One thing on the forks is you might want like a small triangle support or another bar to support where the bar comes out of the front. At the moment it looks like it would be particularly vulnerable to having the front bars bent where they are attached.

If you intend to fight spinners with the design, unless the little wedges on either side at the front are seriously tough, those corners are spinner heaven. Maybe something like this?

http://s18.postimg.org/u919erl4p/loki_flatweapon.jpg

looks good, if it was me thou definatly go 4 wheel drive as robots with drive wheels at the front are dreadful to drive! or perhaps have wheels in the middle

Thanks for the feedback guys, lots of things to think about. See if I can squeeze some more motors in :D

Fantastic design, I like the shape with the wedge rather than forks (spinners and so on).

Time for another update, it's a been a little while.

Following fellow roboteers' advice, I have moved the wheels to the middle of the robot and is a lot easier to control now so thanks! (I considered 4WD but with the current design there isn't enough space with the actuator in the position it's in).

I've moved the removable link and power LED to the top as I want to but diagonals to join the wheel sides to the back for a bit more protection for the gubbins (if that even makes sense, so it would look like the CAD on not the 'T shape' it is at the moment).

I've also made some armour out of the ally off cuts I have and had a go at painting to see how my paint looks. I'm liking the results :D The armour is a little short, I'll blame it on the limitations of the size of the off cuts and not my poor measuring skills :P Making mistakes and learning lessons every day!

I drilled out the hole in the actuator from M6 to M8 as it kept bending the M6 bolts.

It can now successfully self right with just the front bars (not been able to test it with the main lifting bar yet, hoping it will self right like Biohazard did back in '96).

Actually have a question, is there a better way of attaching the armour rather than screws? Or will the screws be adequate?

And that's it for the moment, should be getting more ally bar in the post tomorrow so will be able to make the other arms of the lifter.

Here's some photos for your viewing pleasure :)

http://i1298.photobucket.com/albums/...ps3f96901c.jpg

http://i1298.photobucket.com/albums/...psce3d5921.jpg

http://i1298.photobucket.com/albums/...pse121e389.jpg