jes's build log

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jes
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Re: jes's build log

Post by jes »

I've finally made some wheels with silicone rubber tyres. I bought some 2-part silicone rubber off eBay, it is described as being a 5 on the "Shore A" hardness scale. The plastic inner of the wheel has some holes in it so that the silicone is physically attached to the wheel:

ImageImage

Yesterday I printed a test wheel and a mould and poured some silicone:

Image

The mould is PLA because I read that silicone sticks to nylon and doesn't stick to PLA. Turns out it doesn't stick to the nylon very well either, but at least the holes in the wheel ought to keep it in place.

I found that the silicone was not viscous enough to avoid leaking through the holes in the mould, and also the tyre is much too "deep", making it too soft and flexible because it is not sufficiently supported by the plastic. I also thought it would do better with a "tread pattern" on the tyre.

I made the plastic part of the wheel larger so that the silicone layer would be smaller, added a tread pattern to the mould, and made 4 copies of the wheel and the mould. You could use just 1 mould and do the 4 tyres sequentially, but the silicone takes about 4 hours to cure and it is much quicker to print extra moulds than to wait for the silicone to cure.

This time I sealed up the moulds with hot glue to stop the silicone from leaking out the gaps.

Image

The clamps are to hold the wheel down to the mould, as the silicone is denser than the (mostly hollow) nylon wheel.

After the silicone had cured I peeled the hot glue off, then peeled the mould off, trimmed off the excess, and now I have 4 nice rubbery tyres:

Image

Oh, and I've cured my Taulman 910 problems. It prints beautifully. I find that printing at 245 prints just as well as at 260 and does overhangs better, and heating the Ultrabase bed to 45 degrees instead of 60 makes it stick to the bed better. I don't know why it sticks better to a colder bed, but it suits me as I don't have to wait as long for it to heat up. At 245 with a 45 degree bed, I don't need any raft or brim, it sticks just as well as I'm used to with PLA.

Increasing the clearance for the wedge pivot has made it move nice and freely now, so I think the robot is almost ready. It's about 1g overweight because one of the chassis halves was printed a bit heavy, so I'm printing another chassis half with my final print settings (which is 8% infill, 2 bottom, 1 perimeter, 3 top, and oriented the same as the "top" half of the assembled robot) and then I just need to get better at driving it :)

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Kyro
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Re: jes's build log

Post by Kyro »

that is looking really good...

i wish my first bot looked as good as this one... i guess thats the benefits of 3d printing.

i cannot wait to see it in action at antfreeze.
Team Rocket
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Mantis (4wd grab 'n' lift)
Dominus (Vert SPINNAAH)
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jes
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Re: jes's build log

Post by jes »

Thanks! I look forward to trying it out at Ant Freeze :)

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LimaHotel
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Re: jes's build log

Post by LimaHotel »

I do suggest you try the old polycarb and hacksaw approach to building. It's just a totally different experience, and the bit that I personally really enjoy.
It looks scarily good though man. Have you fixed the pivot issue?
Jiggy Sawdust
Jammin' Good with Weird and Flippy
The Pushbot from Mars

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jes
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Re: jes's build log

Post by jes »

Yes the pivot issue seems solved. Increasing the clearance was enough. It's not really as smooth as I'd like, but I'm relatively confident it won't get stuck, so it's good enough for me.

I can certainly see the appeal of making stuff by hand, and perhaps I will make an antweight by hand one day. I looked down on 3D printing for quite a while because I thought it was silly to have a machine print parts when I'm perfectly capable of making an equivalent by hand. But eventually I realised that I enjoy designing things much more than I enjoy making the parts... each to their own.

And I filmed a demo of the robot working in case anyone is interested: https://www.youtube.com/watch?v=0_t4P_eA-ds

It has a power switch at the back, but no LED to indicate when it is powered on. I think this is fine, by my reading of the regulations, but I do recall reading somewhere that a power indicator light is required?

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MarkR
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Re: jes's build log

Post by MarkR »

A power-on LED is not required in the Ant class, I think it's mandated in the heavier ones.

One piece of advice: Make the two sides of the robot easily distinguishable, put a big white X or something on one side. Otherwise, you might get turned over several times and not be sure which way up you are.
Robots: Betsie - RaspberryPi controlled flipper bot with gyro stablisation - too clever for her own good?
Stacie - tidy flipper; 4wd driven by hair bands

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jes
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Re: jes's build log

Post by jes »

Agreed, that's a good idea.

I've already surprised myself by accidentally driving off the table, putting the robot back on, and then driving straight off again backwards!

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Ocracoke
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Re: jes's build log

Post by Ocracoke »

A power-on LED is not required in the Ant class, I think it's mandated in the heavier ones.
It certainly is in the Beetleweight and heavier classes as per the FRA rules. As noted, it is not required in the Antweight class but I find it good measure to have *a* light somewhere, even if it is the one from the receiver or speed controller somewhere to say the robot is on as an advisory. More than once I've been caught out by that.
Team Kaizen

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MarkR
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Re: jes's build log

Post by MarkR »

I've driven off the table plenty of times...

I always remind myself, or anyone else nearby, that if a robot can't survive being driven off a table on to the floor, it's not going to do very well in the arena :)
Robots: Betsie - RaspberryPi controlled flipper bot with gyro stablisation - too clever for her own good?
Stacie - tidy flipper; 4wd driven by hair bands

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LimaHotel
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Re: jes's build log

Post by LimaHotel »

A quick query: how're you gonna acetate that wedge? Are you gonna acetate that wedge?
I look forwards to meeting you in the arena! (That shape looks nicely Jiggyable :lol: )
Jiggy Sawdust
Jammin' Good with Weird and Flippy
The Pushbot from Mars

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