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View Full Version : Mars Lander Rubberband Solution


Bruce Temple
03-21-2006, 07:30 PM
I just got a incomplete & part built up Mars Lander on Ebay for cheap as a builder project. (yes, of course I got a Semroc one too hense the thread) I remembered the guys great idea to mount the body as all one peice with 4 small screws, so you could take it off, and work on the legs & replace the rubberbands.

I just mounted 4 small basswood blocks for the screws to go into. I also used balsa for the supports since its going to be a flyer & wanted the extra durability.


Cheers, Bruce

sandman
03-21-2006, 07:34 PM
I finished all the subassemblies on my Mars Lander while I was waiting for the paint on the legs to dry.

I have not varied one bit from the plans...until now.

Nothing serious but the issue of the rubber bands eventually failing had me bugged and I wasn't happy with that part of the design.

I haven't done a lot of research into what alternate ways other people have used to solve this problem on the Mars Lander so I looked at the solution to this problem in a different way.

Most people seem to come up with a way to remove the bottom so they can change out the rubber bands when they start to deteriorate and fail.

My solution was a bit different. Instead of making the rubber bands ( a weak design to me) easy to replace, why not replace the rubber bands with something a lot more durable. Metal springs!

Everyone has a junk drawer in their kitchen with at least 4 if not 40 old ball point pens that don't write. I know I do!

They all have perfectly good springs in them. I know they are designed for compression but they will work just fine under tension.

A little work with a pair of needle nose pliers and the pic below is what I came up with.

The rubber band design is on the right and the coil spring design is on the left.

Nothing is glued together yet. The spring is a tiny bit weaker than the rubber bands but I haven't adjusted it yet.

What do you guys think?

Bruce Temple
03-21-2006, 07:40 PM
Another great Idea too Gordon! Pen Springs..............AWESOME!

Cheers, Bruce

sandman
03-21-2006, 07:51 PM
And cheap too!

I was gonna throw those pens out anyway.

Now I have a bunch of spring in a tiny drawer in my shop.

Maybe I should have saved the rest of the pens. :confused:

kurtschachner
03-21-2006, 08:44 PM
I also built one a couple of years ago from a partially built kit I got on eBay for cheap. Fortunately the guy did not glue anything together that couldn't be cloned so I was able to rebuild/complete it and it is identical to an original.

Anyway, I did the spring and plastic hinge modification that was mentioned before from that guy's website. Here is a picture of the springs and of the completed model. I never had the guts to fly it, that is what my Semroc kit will be for.

BAR_Daddy
03-22-2006, 08:03 AM
kurtschachner, that is awesome.

Where did you get the hinges and springs?

kurtschachner
03-22-2006, 12:12 PM
kurtschachner, that is awesome.

Where did you get the hinges and springs?

I got the hinges at a local hobby shop and the springs at the hardware store. Like the guy on the website said, you just have to check out the springs and find some that feel like the rubber bands. It wasn't too hard really.

These are the hinges (#307 IIRC):

http://www.robart.com/Hinge.aspx

and the springs were generic hardware issue from the big drawer full of different ones.

One point though, you MUST be sure the hinges are glued in exactly so that the plane of rotation is parallel to the leg. Otherwise the legs will move up and down at an angle to the completed model and may even rub against the side of the exit.

Another thing, the springs have to be a little more strong than you might think. Remember, they have to support the whole weight of the completed model without sagging. You really don't want them extended out when it is sitting.

Here's that guy's page again:

http://www.geocities.com/CapeCanaveral/Launchpad/7721/mlconpg.html

ScooterM
03-31-2006, 12:15 PM
kurtschachner, that is awesome.

Where did you get the hinges and springs?

Take it from someone who's had the pleasure of seeing Kurt's work close up at NARCON the last couple of years; he is a total craftsman! I saw his Estes Andromeda clone last year and his Centuri Mercury Redstone this year and both are just impeccably clean builds. That's what amazes me when I see his work, just the refined cleanness, an almost understated-elegance of the finish--really nice!

dwmzmm
04-01-2006, 04:35 PM
And cheap too!

I was gonna throw those pens out anyway.

Now I have a bunch of spring in a tiny drawer in my shop.

Maybe I should have saved the rest of the pens. :confused:

I used the spring from throwaway pens to build my first ever flexie for last December's
Winter Regionals NAR Sanctioned contest here in Katy, Tx. Worked like a charm, and made
it possible for the flexie to be totally enclosed in my vintage CMR Paratrooper during boost.