Looking for solution and expertise on this crazy idea...

sg219 · Post by **sg219** » Mon Oct 22, 2007 10:21 pm

I'm looking for a solution or an answer to a "what if".

I'm trying to make a form of "dig" for one of my crawlers. The idea seems a bit difficult to accomplish, but I think it is VERY do-able with the right amount of research and open-minded thinking.

I wish I had drawings to show you guys, but I just DL'ed a CAD program and have no idea what the hell I'm doing with it yet.

If someone could suggest a good, simple read on how to use one, or if I should be using something else. I don't need anything real technical, just something to get ideas down and presentable.

Here is my what if...

What if I used magnets to repel against each other to push apart two small "pegs" or "engager's".

These are the custom sliding drive shafts that I made out of aluminum tube, rod, and some steel Traxxas yokes.

I want to insert two thin flat pieces of brass, or something else that is non-conductive, from about 1-2" long into the end of the rod part inside the tube.

Then attach two small magnets to the inside then. So you would have a rod with to thin pieces stick out back to back with a small magnet in between the two tips of them.

Then attach two pieces of metal to the outside of them. So when the magnets repel, they push the metal apart and into the notchs on each side of the tube part of the shaft. This would intern, lock the drive shaft and give you 4WD. Then when the magnets are not repelling, they would disengage and leave the drive shaft free spinning.

That is what I want to accomplish.

My problem is...Is it possible to have the magnets be able to repel via a small electrical charge? Like an electro-magnet, put a charge to it and it holds/repels.

How much current?

What kind of magnets or device would I need to do this?

I'm pretty sure I can get the power there pretty simply.

My other method was to use a ring magnet big enough to go over the drive shaft, connected to a servo and to slide up and down the drive shaft to pull the pieces apart and into locked position. Then move it away to spin free.

This "dig" set-up would give you 4WD, and free rear wheel 2WD.

Next part of this set-up is how could I lock the rear wheels? So I could drag them. But I need to get this far first.

Another method was to put the two pieces of metal into the end of the rod and have them be able to slide up and down inside the rod. I would connect them inside the tube at the bottom onto a pin that would stick out of the rod on both sides. Then use a servo connected to two rings that would be on both side of the pin so that it could still spin, but yet still be able to move up and down.

If this is sorta hard to grasp, think of the brake system on a BMX bike. Particularly the lower handle bar area. The "gyro", I think they used to be called. It lets the shaft spin freely, while also being able to pull or engage the brakes on the other side.

My idea is something like that, the pin at the bottom would be the space between the top and bottom of the "gyro" and the two rings would move that pin up and down to engage the pieces of metal to lock the drive shaft. Think of the spring action thingy on an umbrella. The little "half a rain drop looking thing" that locks the umbrella.

I hope some of this makes sense. I fully believe its do-able, I just need a little more.

Thanks,

SG

SHAUN · Post by **SHAUN** » Mon Oct 22, 2007 11:14 pm

I would get a R2 with disconnect. Its the most reliable and its completely out of the way.

sg219 · Post by **sg219** » Mon Oct 22, 2007 11:18 pm

SHAUN wrote:I would get a R2 with disconnect. Its the most reliable and its completely out of the way.

No shit. Thats nice.

In case you didn't notice, I'm not asking for items that all ready do this. I want my own set-up! I trying NOT to buy something that IS NOT the most reliable.

SHAUN · Post by **SHAUN** » Mon Oct 22, 2007 11:58 pm

Are you planning on leaving the dig with free wheel or with a brake?

Murdoch · Post by **Murdoch** » Tue Oct 23, 2007 12:21 am

ok I see where you're going with this.

essentially you want to recreate a solenoid inside the shaft. Have a look at how those are made. you'll also want to have two ring contacts on the shaft, but those will have to be waterproofed.

sound about right?

evoraptor · Post by **evoraptor** » Tue Oct 23, 2007 12:37 am

What exactly is a "dig"? Not sure on these terms, but from what I'm reading here, you want something that can disconnect when you need to?

Maybe a one way diff, with a way to lock it out.

betty.k · Post by **betty.k** » Tue Oct 23, 2007 2:28 am

i'm not fully understanding this, but as for the electro magnet idea something that comes to mind is microsizer steering. use one magnet and one steering coil.

but i spose you've thought of that.

sg219 · Post by **sg219** » Tue Oct 23, 2007 1:21 pm

Murdoch wrote:ok I see where you're going with this.

essentially you want to recreate a solenoid inside the shaft. Have a look at how those are made. you'll also want to have two ring contacts on the shaft, but those will have to be waterproofed.

sound about right?

I did a brief reading on solenoids then did a little bit of searching. I think something like that would work, but I don't think they make them small enough.

As far as waterproofing, How necessary would that be? I would only be using this truck for comps, and they are almost always pretty dry.

Could you elaborate a bit on what your thinking? I think your onto something.

You wouldn't have a link to some info? Something specific I may not know about, that you do know about.

evoraptor wrote:What exactly is a "dig"? Not sure on these terms, but from what I'm reading here, you want something that can disconnect when you need to?

Maybe a one way diff, with a way to lock it out.

Dig is used on the rock crawling trucks.

It is when you dis-engage your rear drive shafts to allow your front wheels to keep moving and pull your truck around in tight spaces. The rear wheels will pivot and drag instead of rolling or driving the truck in the direction of the front wheels.

It comes in REALLY handy during a tight turn on a comp course.

I think I explained that right.

betty.k wrote:i'm not fully understanding this, but as for the electro magnet idea something that comes to mind is microsizer steering. use one magnet and one steering coil.

but i spose you've thought of that.

No I didn't think of that......damn.....

That is the kind of thing I needed.

How hard could it be getting that inside the drive shaft tube....

........................................................................................

Post a link or two if you think its useable info. I'm all about learning and doing a bit of reading.

Keep the thoughts coming.

I like where this is going.

Thanks for the suggestions and ideas.

sidewinder · Post by **sidewinder** » Tue Oct 23, 2007 2:08 pm

What if you used something like these: http://scientificsonline.com/product.asp_Q_pn_E_3082273 maybe use them in one end and a electromagnet in the other. when power is supplied it will either repel or attract depending on the poles.

Murdoch · Post by **Murdoch** » Tue Oct 23, 2007 10:55 pm

holy CRAP did the board ever take a long time to load just now.

anyways..

If you're running your rig on dry ground only, it should be okay if the contacts are exposed.

basically you'll need two sliprings and brushes. Same thing as an AC motor or alternator.

Coil goes on the outside shaft and the ferrite core is stuck on the inside shaft.

Hit it with power and the ferrite core gets sucked inwards. You can stick in a spring to push the core out when you need it to freewheel.

Here's a ton of 'em. http://www.allelectronics.com/cgi-bin/c ... noids.html