First antweight (want to check if im on the right track)

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danjr1
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First antweight (want to check if im on the right track)

Post by danjr1 »

Hey,
Been sketching up my first antweight and I just want to run the specs past everyone to see whether im on the right track or not so here goes:

*1 and 1.5mm bonded carbon fibre monocoque chassis/ armour - approx. 34g. May add a little 0.8mm titanium to the mix as well if weight allows with some home-made anodization?!
*4 x 400rpm gearmotors - approx. 10g each (http://www.ebay.co.uk/itm/Diameter-12mm ... 1e7c2db8ad)
*4 x servo board ESCs - approx. ??g each
*4 x pololu motor brackets - approx. ??g each (does anyone know of the metric sized nuts and bolts id need to replace the weird American ones?)
*1 x 2s 200mah turnigy nano-tech battery - approx. 10g
*1 x micro receiver - approx. 1.6g (http://www.ebay.co.uk/itm/Ultra-Light-D ... 2c6cd7f3c7)
* 4 x 18mm wheels - approx. ??g (http://www.usahobby.com/robotics/gearbox.php/1)

I could replace the carbon fibre with HDPE of the same size, that would roughly halve the weight of the frame but the weight at the moment, from the weights I know, is 86g and that's without the servo boards, motor brackets and screws, wheels and some method to lock the lid on. Im thinking it should be in weight but if others could let me know what they think, it would be really appreciated.

Cheers
Dan
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BeligerAnt
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Re: First antweight (want to check if im on the right track)

Post by BeligerAnt »

Hi Dan

The list looks good. The nearest metric screws to the ones for the Pololu brackets are probably M2.5 although AFAIR the screws and nuts are supplied with the brackets. Alternatively a couple of small cable ties work really well...
Gary, Team BeligerAnt
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peterwaller
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Re: First antweight (want to check if im on the right track)

Post by peterwaller »

Hi Dan
As Gary says the list looks OK in fact you seem to have found a small cheap receiver I wasn't aware of.
Having looked into it a bit that receiver looks like the one from LemonRC. I think it is meant as an alternative to the Orange ones.
I havent tried them yet but have put some on order to try out and I will put my findings on the forum.
If they are the Lemon ones you can get them much cheaper ($5.75) direct from lemonrc.com with the connectors already soldered.
http://www.lemon-rx.com/shop/index.php? ... duct_id=65
The P&P is another $3.80 but I ordered 5 and it didn't increase.
danjr1
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Joined: Fri Sep 03, 2010 11:54 am

Re: First antweight (want to check if im on the right track)

Post by danjr1 »

Cheers guys. have ordered the motors already so im just working through the list.

I need to create a DXF file of my chassis parts which i can easily do in tinkercad but i think that will create a file for 3d printing. Does anyone know of a very easy (and free) way to either convert the existing file or create a new DXF file?

Cheers

Dan
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peterwaller
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Re: First antweight (want to check if im on the right track)

Post by peterwaller »

I don't know Tinkercad but on their site they say it supports 3D printers that use STL files which is most of them so I would go for that.
Most of us use Google Sketchup for 3D drawing because its free but then have to convert the file to STL using another package.
danjr1
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Re: First antweight (want to check if im on the right track)

Post by danjr1 »

Need a little help on wheel fitment. I'm using the Sanyo style motor with the 3mm output shaft and the wheels I've got have a 2mm axle bore. To get a decent fit, what would I need to bore the axle hole out to? I was thinking 2.9mm but wasn't sure?

Also, what plastics bond well with epoxy?

Cheers!

Dan
razerdave
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Re: First antweight (want to check if im on the right track)

Post by razerdave »

Hey Dan

Usually people use wheels with D shafts already in them (pololu white 32mm ones), but otherwise, you can drill a 3mm hole into a wheel and use a grub screw through a boss to hold it on. Either that or drill a bigger hole and use a collar of metal like Simon does on the old Dynamite lego wheels.

Also, generally speaking most glues don't hold well with plastics. Best thing is bolts or HDPE welding if you want to go that way.
danjr1
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Re: First antweight (want to check if im on the right track)

Post by danjr1 »

Don't think the wheels have room for a grub screw! They are 18mm OD diameter and 9mm wide. Might bore them out to 3mm and put a little epoxy putty in there maybe to fit to the flat of the shaft? Will just have to keep working at it! Cheers!
haz
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Re: First antweight (want to check if im on the right track)

Post by haz »

I've glued plenty wheels on.. probably incredibly bad practice but I've not had too many problems :)
danjr1
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Re: First antweight (want to check if im on the right track)

Post by danjr1 »

I haven't been clear, sorry!

I'm planning to attempt bonding a small amount of plastic to the CF frame to act as the material to screw into to hold the lid on. Had a google and I think that using PVC with epoxy MAY work but we'll see.

In terms of the wheels, I'd like to use a tight interference fit on the motor output shaft so I think the only way to do it will be to bore the axle holes out to 2.9mm. There's just not enough plastic in the wheels to use any other method. I could then possibly use a tiny amount of epoxy putty to mold to the shape of the shaft and maybe some good liquid loctite once it's dry.
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