Big wheels on a heavyweight

[craig_colliass]

Im looking to make the next robot with large wheels similar to a car (500 mm diameter) the wheels will be exposed what do the forum recommend,
1/ a ridged wheel that wont bend.
2/ a more flexible wheel that distorts with the knocks and springs back.

[maddox]

Big wheels on a heavyweight

Prime example. The wheels from Tough As Nails.

The originals still are in use. Yes, that one lost that the rim in Series 7. The same that got a nibble a few months before from Kan-Opener in Rijswijk.

Flexible wheel are my reply then.

[Guest]

Big wheels on a heavyweight

Have flexable ones...........barbarous are another example with flexy wheels.

[craig_anto]

Big wheels on a heavyweight

its swings and roundabouts Craig, TAN has flexy wheels and will degrade under attack but will stay on (mostly)
My (Tanto) has hard more solid wheels they with stand alot of punishment tyres can degrade but wheels stay on,
I would suggest a solid centre slightly larger than the dia of the body of the robot (assuming u go invertable like tanto) with soft tyres that way if u loose your tyres it will still work.

but with 500mm your proberbly better going for flexible lighter wheels

[swanaldo]

Big wheels on a heavyweight

hells teeth 3 with the monochassis made from stainless had huge wheels. we tried to make them rigid and brace them but still bent. still it did run well. i would go for flex too. i liked that robot too.

[craig_colliass]

Big wheels on a heavyweight

What plastic makes good flexible wheels?

[swanaldo]

Big wheels on a heavyweight

been sat here thinking of how to make some flexi wheels. here is my plan.

get some nice 15mm polypropolene and cut out 2 circles of whatever dia you wish. lets say 400mm. then drill a hole for the shaft. mabee 30mm holow shaft fot a bit of strength. make a carrier to hold the 2 pieces of poly to the shaft a bit like a kart setup. space out the 2 pieces of poly to about 80mm. between the poly put in springs so the 2 pieces will have flex but then add a bit of strength. then get a nice thick piece of tyre and screw it to the 2 pieces of poly around the outside. when the wheel flexes the tyre should flex with it.

is that a bit too much work for some flexi wheels???????

[tom_kane]

Big wheels on a heavyweight

nylon

[leorcc]

Big wheels on a heavyweight

HDPE

Its what is used on TAN, still the same wheels since series 7.

[swanaldo]

Big wheels on a heavyweight

dont like my genius plan then :sad:

[tom_kane]

Big wheels on a heavyweight

Its genius, doesn€™t include gaffer tape though

[craig_colliass]

Big wheels on a heavyweight

Shane I dont know about the springs, but the rest seems quite brilliant!!!!!!!!!!!!

I was thinking about using the ctr of a car wheel say 200mm dia then bolting the plastic to each side of that (with spacers to get the 80mm) then fitting some type of tyre perhaps a Motorcycle tyre what do you think?

I have bought some trailer hubs for the stub axels they are quite light but very strong the stud pattern is 100mm 4 stud.

[maddox]

Big wheels on a heavyweight

HDPE has several advantages in this application.
Easely worked, very light, flexible but springy, even limited self repair capacity, and contradictionary to the easy worked and softness, very tough. Easely damaged, almost impossible to destroy. What is demonstraded in the TAN wheels, in use since 2002, and its not that TAN was left in the shed for all those years.

These wheels are made from a 12mm HDPE plate, turned to fit in the thin walled 16 drainage pipe, with a bit of messuring and tapping with a hammer the plate was at the right depth straight and then welded in.
Then we put the wheel in a large chuck on the lathe and finished it so it was straight in all dimensions, a nice centring hole to fit the custom Hubs Kos turned and milled to perfection.
The first set of wheels used the surface of a rather soft and worn cartyre fixed with short wide head woodscrews. But the thickness of rubber and steel braid in it makes this a very heavy option. Also, car tyre is made for cars, not 100 kg robots,the grip is less than optimal.
Other option we tried.
Running surface from a wheelbarrow wheel. Not grippy enough, but very light.
And since then we have a formula One style mounted set of wheels.

But the best result on wheel surface coating was my first experiment in that respect, the billet HDPE backwheel from Project Two: Hexem, what was fitted with the softest compound dirtbike mud tyre we could lay hands on. Kevlar reinforced, thin rubber, high studs and so grippy it glued itself to the floor.
But the main disadvantage, and the reason we didnt do that on TAN, was the pricetag, and TAN would have needed 2 of these tyres.

[swanaldo]

Big wheels on a heavyweight

the idea of the springs between the poly would let it flex but tie the 2 bits together. if you did it with quite strong springs it would allow flex. would absorbe energy when another robot impacted with them too. if i were to redesign the wheels for that version of hells teeth knowing what went wrong i would do them like that. but then experimenting with other ideas is a good thing too.

[craig_colliass]

Big wheels on a heavyweight

now i get it thanks Shane.