Another New Antweight..

All things antweight

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EpicentrE
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Re: Another New Antweight..

Postby EpicentrE » Thu Jan 16, 2014 7:54 pm

I'm sure someone can correct me, but to my knowledge there's no difference in 2.4ghz systems. Because of how 2.4ghz works there's no risk whatsoever of interference and therefore regulations splitting the two classes aren't required. Are you sure your other receiver is DSM2, and not just DSM?
Scott Fyfe-Jamieson, Captain of Epic Robotics. Champion of AWS38/41/42.
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Re: Another New Antweight..

Postby peterwaller » Thu Jan 16, 2014 8:30 pm

As I understand it the two are not compatible due to the difference in frame rates.
I think the basic DSM2 part is probably the same but the ground unit have a faster frame rate which is possible because they are limited to 3 channels.
With air systems the frame time is about 22 ms allowing upto 10 channels but the ground systems run at about 11ms on three channel and and 5.5ms on two channel giving faster response to changes of stick position.

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Re: Another New Antweight..

Postby EpicentrE » Thu Jan 16, 2014 8:50 pm

You're a font of knowledge Peter, and I apologise for my misinformation above. Most interesting.
Scott Fyfe-Jamieson, Captain of Epic Robotics. Champion of AWS38/41/42.
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Rapidrory
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Re: Another New Antweight..

Postby Rapidrory » Thu Jan 16, 2014 9:00 pm

Well the two I've got are

http://www.hobbyking.com/hobbyking/stor ... eiver.html

and

http://www.hobbyking.com/hobbyking/stor ... eiver.html

They do say ground and air, and that they only work with ground or air transmitters respectively...

Shame about that; the 3 channel one was the more expensive and better fitting... at least i know why it doesn't work now, Cheers peter :)
Rory Mangles - Team Mangler

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NanoTwo antweight speed controllers. (viewtopic.php?f=1&t=2128)

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Re: Another New Antweight..

Postby Rapidrory » Fri Jan 17, 2014 6:14 pm

Ok, so word of warning: http://www.hobbyking.com/hobbyking/stor ... _0_12.html do not make good weapon servos... Tried to flip something heavy with one in my flipper, and stripped the gears instantly... the servo's now pretty much useless... woo.

So... back to hunting the internet for suitable servos... :-?
Rory Mangles - Team Mangler

Robots: Too Many...

NanoTwo antweight speed controllers. (viewtopic.php?f=1&t=2128)

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Re: Another New Antweight..

Postby peterwaller » Fri Jan 17, 2014 7:58 pm

I have had some success with this servo.
http://www.hobbyking.com/hobbyking/stor ... duct=29628
While only being 1.8kgcm as opposed to 3kgcm it is all metal gear and I have them in one of my drive all day flippers and the one with pincers.
Image
Image
At £3.54 they are good value and they are in stock in the UK hobbyking warehouse.

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Re: Another New Antweight..

Postby Rapidrory » Fri Jan 17, 2014 8:55 pm

I've stuck a http://www.hobbyking.com/hobbyking/stor ... Servo.html in there, which is the servo from Tinny.. It works fine for the moment, and has UK stock so if I can't find one with better spec, i'll get another one of these to use...
Rory Mangles - Team Mangler

Robots: Too Many...

NanoTwo antweight speed controllers. (viewtopic.php?f=1&t=2128)

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Re: Another New Antweight..

Postby Rapidrory » Wed Feb 12, 2014 11:08 pm

Ok, so I'm having a few issues with flipper linkages; I've tried all manner of different combinations, and I'm struggling to get enough travel for the robot to self right, whilst still having enough power to flip anything properly... I've tried 3 bar and 4 bar linkages, and none of them have had enough travel really.

This is the setup I have atm:

Image

And this is it at full extension:

Image

It will just about self right if it is at the right angle and with some fancy flipper work, but the linkage is rather complicated and it won't close properly... Should be better when i get my proper ESC installed so there's less cables in the way, but even so it's still not ideal. Don't know about it's flipping power, as it's just a mock up with paper clips so they'll bend if i put too much load through it, but it seemed to have a reasonable amount... Any ideas for a better set up?
Rory Mangles - Team Mangler

Robots: Too Many...

NanoTwo antweight speed controllers. (viewtopic.php?f=1&t=2128)

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Re: Another New Antweight..

Postby EpicentrE » Wed Feb 12, 2014 11:23 pm

Rory,

what I often do if I'm having trouble self-righting is put some "horns" on the top of the machine so it holds itself further off the ground when upside down, meaning you need less travel in order to self-right.

I'd definitely wait until you've got some proper materials (not paper clips) before making a final judgment, but my experience with sliding-bar flippers, such as your design here, has been less than stellar. The most common and most successful flipper linkages are designed like the bottom two images on this page. This kind of design also gives you a lot of flexibility as you can easily move the hinge points around to find the perfect balance of travel, speed, and power. Gary describes it very well on the page linked above

Best of luck :).
Scott Fyfe-Jamieson, Captain of Epic Robotics. Champion of AWS38/41/42.
http://www.epicrobotics.co.uk

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Re: Another New Antweight..

Postby Andrew_Hibberd » Thu Feb 13, 2014 12:00 am

I can only add that with the linkage method on Garys page the servo horn can be extended to give even more flexibility on the linkage travel.

You can use a compass on paper or a cad sketch to find the designed angles and lengths.
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Rapidrory
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Re: Another New Antweight..

Postby Rapidrory » Thu Feb 13, 2014 1:30 am

Yeah, i plan to add horns, but even with something under the robot to emulate horns, it struggles to self right; the center of mass is too far back so there's very little momentum to carry it over.

I'm using heavy duty paper clips which use about 1mm diameter steel rod. It's doesn't bend as long as you don't try flipping anything too heavy with it; the robot can attempt to self right fine without them bending the temporary linkages.

I've tried all the linkages shown on that page previously, and have also tried extending the servo arm, and the current setup has the best balance between power and travel in this case.

One of the problems with a 4 bar linkage is that with such a shallow flipper angle, you have almost no power in the flipper when it's just starting to open; exactly when you need it...

However, with a 3 bar linkage, it's hard to rig it so the servo pulls the flipper back down, and the ability to grab using the flipper is one of the strengths of this robot. The setup I have atm works ok, but isn't very reliable as you can probably imagine... If I went without self righting, then it would be relatively easy to set up, but then that would be a pretty major weakness...
Rory Mangles - Team Mangler

Robots: Too Many...

NanoTwo antweight speed controllers. (viewtopic.php?f=1&t=2128)

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Re: Another New Antweight..

Postby EpicentrE » Thu Feb 13, 2014 8:49 am

Looking at your pictures again, I think the main problem is just not having enough travel. If you wanted to stay with your current design, I'd look at shortening the linkage from the servo so that the slider starts further along the flipper arm and finishes closer to the hinge. If you were going back to a 4-bar design, then I'd look at making the distance BD equal to or shorter than distance AC (refer to the diagrams on the page linked above). Assuming your servo moves through 90 degrees, then if BD=AC your flipper arm will also move through 90 degrees, which should be enough to get you back on your wheels. If its getting stuck on it's back, you could look at adding something small and circular to the rear so that it's encouraged to smoothly roll back onto its wheels.
Scott Fyfe-Jamieson, Captain of Epic Robotics. Champion of AWS38/41/42.
http://www.epicrobotics.co.uk

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Re: Another New Antweight..

Postby BeligerAnt » Thu Feb 13, 2014 7:31 pm

The same article that Scott kindly linked to, but on my new site:

http://garya.org.uk/antweight-robots/te ... r-linkages
Gary, Team BeligerAnt

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Rapidrory
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Re: Another New Antweight..

Postby Rapidrory » Thu Feb 13, 2014 9:12 pm

I might have a look at doing a 4 bar linkage moved further back, though i'm concerned that the servo wouldn't have the torque for it.. Not that i know how much torque that servo has any more as it's been heavily modded with a more powerful motor and will shortly be converted to run on 8v :wink:
Rory Mangles - Team Mangler

Robots: Too Many...

NanoTwo antweight speed controllers. (viewtopic.php?f=1&t=2128)

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Re: Another New Antweight..

Postby Rapidrory » Sun Mar 02, 2014 5:20 pm

I've given up on trying to get it to self right, especially now my 'franken-servo' has died, so I'm back to a low powered blue one. Instead I've gone back to my original plan and got it to run inverted... it's not ideal as the wheels are lifted off the ground when it's upside down if the flipper is opened, but it does mean it's not entirely immobile when flipped. Also means I don't need as much travel in the flipper, so it can be set up for more power :) It's also been renamed Lionel for some reason... something to do with Denominator already being taken and a few rounds of the robot wars drinking game... :wink:

Tinny (or Curiously Strong Mints as it is registered) is having traction issues; the wheels are right at the front, with the idea being that when you lift someone with the flipper, their weight goes into the wheel, giving extra grip.. However when there's no load on the front, it's like it's driving on ice :S I dunno why, as they're grippy tires and it has plenty of grip when driving backwards... Doesn't help that the current version of my ESC doesn't have motor braking, so you tap the controls and it spins round at least 180 degrees :P

At the moment I have two very much incomplete robots... This is going to be a busy week! :L
Rory Mangles - Team Mangler

Robots: Too Many...

NanoTwo antweight speed controllers. (viewtopic.php?f=1&t=2128)


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