New FW- doorstop

[jonny]

Re: New FW- doorstop

i think maybe you should use more speed 900s and more magnetz

[Danjr1]

Re: New FW- doorstop

nearly ready! am just waiting for the titanium for the leading edges then i can bond the two pieces of the wedge together, and then bond the Ti to that. Sort the wiring out and rebuild the drive units as i want the strongest thread locker on the pinion gears! Frame will need a good clean as well!

[archie2000]

Re: New FW- doorstop

got to see a video of that

[webby]

Re: New FW- doorstop

looks epic! but isnt there a active wepon rule now?

[jonny]

Re: New FW- doorstop

no..

[Anttazz]

Re: New FW- doorstop

If you have any weight left I would put some big weights as close to the wheels as you can, looks like its gonna lose traction very easily and just spin up the wheels.

[Ellis]

Re: New FW- doorstop

Agreed, in fact I'd make the wheels much thicker as well, the amount of wheel currently in contact with the ground isn't going to be anything like enough to make the two motors per side worth it. That said, it should be batty as hell, and entertaining to watch.

[cavecrusher]

Re: New FW- doorstop

having 2 motors per wheel is totaly pointless. especialy on a 2wd robot.... waste of weight, battery capacity, speedos... etc etc its hard enough to get the power down with one motor for 3 wheels...

hmhm, true that

[Danjr1]

Re: New FW- doorstop

i could increase the wheel width but it would require a new frame, armour and wheels. And each drive unit weighs 3 kgs already. When it's finished, ill look at the weight and see!

[Daniel]

Re: New FW- doorstop

ummmm, dumb question. But doesn't the transmited force = normal load x friction coeficient?
I mean increacing the number of wheels won't increace pushing power (theoretically). The surface contact will increase but the force per area would decrease and thus removes area from the friction equation. I'm quoting what I remember from physics lessons and text books. Logic tells me I'm right, but I feel wrong. I mean the reason tractors and machines have wide wheels is to distribute weight of soft ground, not to increase traction. I didn't think smaller point load on the floor was bad in our case. But I still feel wrong.

[ewan]

Re: New FW- doorstop

ummmm, dumb question. But doesn't the transmited force = normal load x friction coeficient?

Ideally (for smooth bodies) this is true, but in the real world of numerous variables there's an issue: friction is created by the interference (on a very small scale) of surfaces, such as a tyre and the road, and with soft rubber tyres you're likely to get very high interference where almost all gaps/ridges in the traction surface are filled by rubber. In this case you stand to benefit by making the tyre wider up until the point that the weight over the wheel is too little to keep pressing the rubber fully into the surface imperfections. Just look at racing cars (with substantially wider tyres than road cars) to see the property in practice (but then you've also got chemical tyre reactions as in F1.. a story for another day).

With this (or any 2WD) design there's obviously not 100% of the weight over the driven wheels, no matter how large they are. I really can't see how this machine can use the power available to it, though it should be very good at spinning it's wheels...

[Danjr1]

Re: New FW- doorstop

need some advice. tested the bot today with its polycarb wedges but they were useless! I'm thinking 5mm steel panels welded together at the point now? problem is that i can't cut, chamfer or weld steel accurately at that size? looking for a little guidance really on how to sort the problem.

cheers

dan

[Danjr1]

Re: New FW- doorstop

not to worry. sorted something that will hopefully work. Will exchange the 5mm polycarb for 5mm HDPE and redesign the side panels so the material is thicker and has a shoulder machined into it so that the wedge and lid panels sit nicely. can HDPE be solvent welded?

[jonny]

Re: New FW- doorstop

have you sorted the titanium for the front yet?

[Danjr1]

Re: New FW- doorstop

yeah. Found a german company on ebay which sorted it for me. Weren't cheap but was exactly what i wanted and they were more than helpful. Bonding that to HDPE should be interesting! hopefully will get it all done for the champs. the thing is setback after setback at the mo and the thought of having a 5mm HDPE wedge (although supported) going up against the spinners is a worry. A slight plus point is that the 5mm HDPE is at an angle so its thicker when viewed horizontally.