Bolts - Featherweight Flail Bot

[maddox10]

No idea how thick is thick enough.
But if I find a way to form a 30mm shell in 1 piece, that will be an experiment worth the trouble.

[emisnug]

No idea how thick is thick enough.
But if I find a way to form a 30mm shell in 1 piece, that will be an experiment worth the trouble.

Vacuum bags around a cast mould perhaps? Kinda like mixing wet lay ups with resin casting

[callumhoy]

The top panel is hinged at the back with gate hinges. The back should hopefully be avoiding most of the damage and the metal will help strengthen the wood, whilst making it easier to access the internals.
Now we finally have a good idea what the wooden top panel looks like.
Wedge.jpg
Bolts currently weighs in at 8.2kg, meaning we still have 5.4kg to play with.
I know for a fact we still have to shape and attach the side panels. Then order the 10mm HDPE to make the added armour and shape the wedge into the point.
If we still have the weight left over, we're hoping to get an aluminium front wedge piece machined (we don't have the equipment to do it ourselves) to strengthen the front.

[callumhoy]

We've been test driving Bolts around a little and noticed something I hadn't expected.
Bolts often struggles to turn. Forwards and backwards works fine, and turning works fine when held in the air with no weight on the wheels, it just struggles to actually turn while driving.
I'm thinking this is because the centre of mass is too far forward, meaning all the weight is too far in front of the motors and wheels.

Am I thinking along the right lines? And what should I do to fix it?

Our first thought was to stick a ball bearing in the front to reduce the friction and push needed to move the front. Would this work? And is there a better way to fix it?

[Roboteernat]

As your turning you have effectively a wedge trying to stick into the ground on the front edge of the wedge. try just smoothing over slightly the edge of the wedge so that as you turn, they ride over the ground.
You may find driving forwards also gets the front stuck at places, but as its a v shape it helps it ride over

[callumhoy]

Thanks, I'll give it a smooth over and see how much that helps

[callumhoy]

The HDPE finally arrived. Now it's gotta be cut to shape and fixed to Bolts.
Planning to cut it with a fine toothed jigsaw, but I'm not sure how to fix it to the wood underneath, any advice?
HDPE (1).jpg

[callumhoy]

In response to the previously mentioned lack of drive when turning, we have a couple of solutions we're considering.

1) Add a ball bearing style roller to the underside of the wedge, reducing friction and allowing easier turning.
2) Double the width of the wheels by bolting two wheels together, increasing grip and contact area on the wheels.

[R9000]

I think widening the wheels might help quite a bit. Adding a roller might lift your wedge too far up off the floor.

Are you attaching HDPE over your wood? Why not just make the entire chassis out of HDPE?

[callumhoy]

We're attaching the HDPE over the wood for a couple of reasons.
Firstly, we've got the extra weight to spare, so we thought why not.

Secondly, extra armour never hurts, especially when we don't have to worry about an active weapon, we want to keep maintenance costs down considering it's our first competing robot.

Thirdly, Bolts may often be lent out to young family members who want to get involved, so we think it's best it can survive multiple matches with as little damage as possible, so they get more enjoyment out of it

Fourth, we didn't think about the HDPE until after we built the wooden chassis.

[callumhoy]

The current plan for the front wedge on Bolts is to get it machined out of aluminium. This should create a strong front, whilst also saving a little on weight.
Any recommendations for which type of aluminium to go for will be greatly appreciated.
Wedge.jpg

[R9000]

7075 is the toughest I believe, but I'd make it out of tool steel or hardox.

[Maxamuslead]

yeah get a steel edge (HARDOX my suggestion). It would keep a sharper edge over aluminium and be should be resistant against damage

[callumhoy]

Tool Steel and Hardox would both take us above the 13.6kg weight limit. The 7075 should hold up, it's solid all the way through and shouldn't be taking full on hits from spinners.

Perhaps a steel edge could be done. I'll have to check the maths on that.

[callumhoy]

If anyone on here has the capabilities to machine 7075 aluminium and has the time and is willing. Please do take a look at the Sketchup files, the DXF file and the included photo with measurements HERE and PM me a quote. I am also sending off for quotes from a couple of local companies, so apologies if I don't reply particularly quickly.
Wedge.jpg