bar exam rebuild

i def like the look of the thicker bars and i would taper both sides so it can be spun both directions in case one side gets worn out or if you have a two way speed controller

Idk we never really had any problems with wearing a drum teeth down but we never really had to many big hits with bar exam any way




Oh and I hate spinning a drum both directions we had a motor doing that last year and I didn't like it
U had to get the stick in the middle to stop it and I would usually over shoot it and spin it the wrong direction
I like it when down is off

you could always flip it around it would work even if the teeth arnt tapered if one side wears out

yah if it comes to that we could do that

I would make the teeth THICK, with BIG radii between the teeth and drum, and spin it in both directions

mlecs drum teeth are all in the 3/4" to 1" wide range.

Reverse operation allows you to test your opponents rigidity, assuming that yours is better, you can break their weapon , motor or other stuff, by spinning nthe wrong way....not for the faint of heart


jmho

rjw wrote:

I would make the teeth THICK, with BIG radii between the teeth and drum, and spin it in both directions

mlecs drum teeth are all in the 3/4" to 1" wide range.

Reverse operation allows you to test your opponents rigidity, assuming that yours is better, you can break their weapon , motor or other stuff, by spinning nthe wrong way....not for the faint of heart


jmho

what u mean with BIG radii between the teeth and drum

the teeth are 1/2 already but i could make it better

and making it spin both directions do you need to have 2 slants on the teeth

where the tooth meets the drum body......there should be a large radius.

Angled, slanted, etc = possibly beter bite, but more prone to chipping. blunt = less bit, but more sturdy and will last longer.....don't be swayed by any of my wierd looking teeth designs, keep it simple

how are you plannin on making this?

Are you having the teeth welded?

Cody Harris wrote:

how are you plannin on making this?

Are you having the teeth welded?

its going to be solid s7
were sending a block of s7 to a machining place .... we would do it our selfs but we cant mill s7

hmmm....

hallboy8222 wrote:

but we cant mill s7

Maybe I'm ignorant, due to my good fortune of having a decent mill, but it seems to me that milling s7 is about the same as milling Aluminum, you just have to
1. use a lubricant (mist systems run as low as $100)
2. Use a carbide endmill (4 flute is good, they might run as high as $20 bucks each)
2. feed the table a lot slower
3. the spindle speed has to be much slower too.

Speeds and feeds are pretty interesting to me--I put together and printed out several excel spreadsheets to guide us in selecting table feeds and spindle speeds with different size endmills on different materials. The only problems I've had since then are ones where I do something stupid (like spin the spindle the wrong way, try to mill material that isn't clamped well, or forget to re-zero the depth!) Recently I've done Titanium and Stainless with good results.

On the other hand, we don't have a 4th axis (rotating table) so we cant do a drum either.

Oh, and VERY important--do NOT touch the chips. Aluminum chips are pretty safe, but chips of steel can cut you, or get embedded your skin. Use a shop vac to clean up.

We have a manual mill and no carbide teeth.....

Very limited sizes on the endmills also...

We could turn steel and also mill some simple stuff in S7 like finalizing the blades we did last year but nothing too complex...

We are going to do some CNCing to all of our 6061 this year on a smaller machine we use for the F1 contest.

I am looking at Steve's drum design and thinking that we could go tooth width of 5/8 wide on the drum and 3/4 wide out by the teeth....

that might give him some wider attachment and an angle on both sides....

I am also thinking that raking back just one side will be the answer.....

Somewhere around 9K tooth speed on this one and 10K on our other vertical disc.

That is if my calculations are right....

FRISCO