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New Builder from Victoria.


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Miss Pigeon



Joined: 11 Jan 2017
Posts: 5
Location: Victoria


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New Builder from Victoria.

Hi, I'm Alexandra I live in Melbourne. 2017 is going to be the year I finally build my first robot and enter a comp. I'm aiming to build a horizontal spinner for the robowars nationals this year with a few friends.

Here are some first drafts. Would love to hear any advice/criticism.

http://imgur.com/BmSvv8g

http://imgur.com/KBIwARi

Post Thu Jan 12, 2017 11:27 am 
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Valen
Experienced Roboteer


Joined: 07 Jul 2004
Posts: 4425
Location: Sydney


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That's actually pretty good!
Only thing I'd suggest is put the wheels as far forward as you can, don't have the bearing sticking through the side panel (when somebody bashes in the side panel your wheels won't work) and make the wheels out of something sticky. That style of design often has big issues getting traction with all the weight being so far forward on the skid.

If you want to put direct images in from imgur, open the image so you get the direct link
say
http://i.imgur.com/KBIwARi.png
put a h after the file name
http://i.imgur.com/KBIwARih.png

then stick it inside the img tags




So the thing for the above picture is

code:
[img]http://i.imgur.com/KBIwARih.png[/img]


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Post Thu Jan 12, 2017 7:43 pm 
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Miss Pigeon



Joined: 11 Jan 2017
Posts: 5
Location: Victoria


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The plan is to use 18v K-mart drill motors for the drive, I'm not planning on having them stick out like the picture, it's really just a first draft. For wheels what do you think about these: https://www.bunnings.com.au/ambassador-100mm-white-plastic-centre-wheel-and-rubber-tyre_p3942885

They look similar to the red wheels but have a slightly larger diameter.

Thanks for the tip about wheel position and the image embedding Very Happy

Post Thu Jan 12, 2017 7:58 pm 
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maddox



Joined: 21 Dec 2006
Posts: 758
Location: Belgium


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Wheels to far forward don't work either.
We tried that with Caliope, but that was an uncontrolable machine.

https://www.youtube.com/watch?v=4JQFl55Wglo

In Nebelwerfer we found the middle road with the wheels inline with the "tip-pich" of the disk.

https://www.youtube.com/watch?v=rSPTnB-8utM

Post Fri Jan 13, 2017 12:44 am 
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DumHed
Experienced Roboteer


Joined: 29 Jun 2004
Posts: 1219
Location: Sydney


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quote:
Originally posted by Miss Pigeon:
https://www.bunnings.com.au/ambassador-100mm-white-plastic-centre-wheel-and-rubber-tyre_p3942885

They look similar to the red wheels but have a slightly larger diameter.




I've used these wheels before, but found the red wheels usually work better.
The white ones are a nice size, but they are pretty flexible and the hub area is not strong enough to transfer the torque from the motor.
I made up a hub using an M10x1 nut welded to a small piece of thin steel. The M10x1 fits on the drill shaft reasonably well.

You can also use parts of the drill chuck to make a more solid hub.
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Post Fri Jan 13, 2017 9:06 am 
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Spockie-Tech
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Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia


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Ive written a couple of times on these wheels as well.
They are what Inspector General used to use..
Definitely not recommended for new builders.

They are *heavy.. so much so you have to drill holes in the tread to try and get the weight down.

The high rotational inertia of them will smash drill gearboxes much faster on full power reversals. If you *must run them, run them *slow (dont bother trying to overvolt your drills for speed, you will just munch gearboxes without heroic efforts to absorb shock reversion loads).

You could probably help a bit with a clever radio and a gentle slew-dampen / ramping on the throttle channel.

As Andrew said, the hubs are way too weak, you need to come up with a system of moving the drive torque point to edge of the rim, not the center or they will strip out.

Yes, they are an easy way to make a thin robot invertible, but they require a lot of work to get *reliable.. you cant just bolt them on and get "reasonable" reliability like you can with the red wheels.

The infamous red wheels are "carefully matched" Wink to the drill gearboxes capabilities. Even just upping the traction significantly with a stickier same size wheel like a colson will translate into drill gearbox problems.. the red wheels hard rubber gives you some slip and stops too much torque from causing drive problems.

If you want to use them, feel free, but be gentle with the motor power or have a good supply of replacement gearboxes on hand ! Smile
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Post Fri Jan 13, 2017 10:54 am 
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DumHed
Experienced Roboteer


Joined: 29 Jun 2004
Posts: 1219
Location: Sydney


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these white ones are not the ones you're thinking of / used in Inspector General.

They're much lighter and narrower than a red wheel, and very flexible.

I used them in Stealth, and the wheel flex was part of the robot's suspension system.
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Post Fri Jan 13, 2017 11:02 am 
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miles&Jules
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Joined: 19 May 2010
Posts: 3959
Location: ipswich QLD


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Great to hear of new builders- welcome-we use 18v kmart drills with 3" colson wheels they are even smaller then redwheels - and we run them in 4s 2000mah lipos and They dont seem to explode anymore so smaller wheels are better on the motors💥
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Post Fri Jan 13, 2017 6:47 pm 
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Ondray



Joined: 06 Jul 2015
Posts: 125
Location: Newcastle


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I have been using the 125 mm white wheels with mixed results. (note you don't want mixed results) I think the 125 mm ones have much stronger hubs than the 100 mm, but I've still got two with broken hubs - admittedly from big hits.

They are much harder to mount than the red wheels, I ended up drilling the hubs out to accept the adapters that sit near the wheels at bunnings. Then it would screw onto the drill 3/8 thread and I'd use the reverse threaded screw with a recessed washer (stronger than standard washer) to hold the wheel on.

A fair bit of work, and I went 4WD on my sportsman because I'd have wheel issues every round. I've converted to 110 mm (1/8 scale) RC wheels...we'll see how the extra grip goes on the gear boxes.

Post Sun Mar 05, 2017 3:01 pm 
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