Lighter than titanium/just as tough. This is a good puzzle 1

[BumpMan]

I am in the development stage of a project that is beginning to focus on materials. To imagine the project picture a 'V' made of 2 individual legs but the right leg is almost 1.5 times longer the left leg of the 'V'. Resulting in a shape thats more like a check mark (?) created by 2 lengths and hinged at the bottom.

The problem is that this ? has to be perfectly balanced.

Assuming the design cannot change and that the goal is to create an entirely metalic object what are my options? Also note that the angle of the 2 must be the same so I can not leverage the shorter piece. Finally the parts get fairly thin is some places around 1/16" with a width of 1/4" and it should maintain its ridgidity even with applied force by hand. This is a fairly small object and Ive tried using Stainless Steel for the shorter half and titanium for the longer part but its still off balance.

Other ideas have been to use foamed titanium or aluminum for the longer half or even using a plastic that would be electroplated to simulate solid metal. I could shell the larger leg and have a solid shorter leg. Im really intrested in new metal materials or processes that might work and look very interesting.

The ultimate goal to use different materials to create balance while still using ridgid materials.

Ive been focusing on how to make the longer part lighter but maybe someone can think of a way to make the shorter part heavier...?

Any Ideas...?

 

[TVP]

The following list provides the density (in grams per cubic centimeter) of the commonly and not so commonly used metals:

magnesium = 1.74 to 1.83 (depending on alloy)
aluminum = 2.69 to 2.83
titanium = 4.37 to 4.82
zinc = 5.00 to 6.60
copper = 8.25 (beryllium copper) to 8.94 (pure copper)
9% aluminum bronze = 7.65
steel/stainless steel = 7.85
lead = 11.35
silver = 10.49
gold = 19.32
platinum = 21.45

Figure out the volume of each leg and then choose the appropriate material to balance them. Moment of inertia will affect this, so the angle between the two legs, and the distance of the center of mass from the centroid will also influence the balance.

FYI, plastics are around .9 to 1.4, and glass is around 2.5. Good luck

 

[mloew]

BumpMan,

This is an interesting problem; what is it for? What methods will you be using to solve this problem? I ask, because it seems to be a good one to use the Behavioral Modeling Extension (BMX) feature in Pro/ENGINEER. TVP has provided you with some excellent material information to get started with.
Best regards,

Matthew Ian Loew

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[BumpMan]

Thank you for your intrest in this problem. This is some great input. Thanks for the density figures TVP. I couldnt have asked for more in this department. I will do some magnesium research right away. Matthew - I have modeled this object in Solid works and have been using the specific gravity feature to begin calculating possible solutions. What does the BMX feature do...? How does it work? Is it similar to the Specific Gravity feature Ive been using?

The problem gets more interesting if I explain it further. You see the object is actually closer to the shape of a 'V' rather than a '?'. Both legs are very similar in length AND volume. Sounds simple. The problem is the bulk of the mass in each leg is in a different place. Picture 2 wedges that vary in thickness from 1/16" to 1/4". In our 'V' model the left leg has its thicker end at the base where the two legs connect. The right leg is of course opposite with its thin end on the bottom and the thicker area at the top offering the right part some leverage and hence making the two pieces together uneven when standing as TVP had explained.

Ive been thinking of using inserts to fine tune the weight issue but lets just say that the Stainless Steel/Magnesium combo doesnt work what could I insert either of the pieces with since I am already using both extremes. The only solution would be to remove some material from the heavier part I assume... Silver/Gold/Platinum seem far too expensive to use for weighting purposes so Im stuck with Steel as my heaviest material. (Again I assume)

What If I weighted the bottom (where the two legs connect)? Could that possibly overide the veveraged counterweight? (Similar to the way those punching clown baloons are weighted and keep comming back for more.

I am also very interested in using new processes applied to metals to solve this problem not just raw materials. The shape can and will slightly change and Im open to ideas like perferating the materials, foaming it, or any other new/novel/technically advanced/inovative ways to solve this.

I am an industrial designer working on this project for a company and unfortunatly can not disclose what this is for untill the project is complete. You know how that is. Again, thanks for your great input so far.
Best,
BumpMan

 

[mloew]

Bumpman,

There is a lot of information on the internet about the BMX functionality in Pro/ENGINEER. Here are some good leads:

http://www.ptc.com/products/proe/bmx/ds_bmx.htm

http://www.google.com/search?num=50...window=1&q=Pro/E+Behavioral+Modeling+tutorial

One of the best demonstrations is to control the position of the CG while varying other geometry. Your problem sounds like an easy one to solve using a technique like this.

The functionality of BMX is similar in concept to that of the "goal seek" function in MS Excel. I do not know of any other CAD software that can do what BMX can do in Pro/E. You might be able to make a macro or some external solver in Solid Works.

This thread is getting a little off-topic for this forum. If you need more specific assistance, I suggest posting a more detailed question in a more appropriate forum.

Good luck!


Best regards,

Matthew Ian Loew

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[BumpMan]

Agreed, thanks again.

BumpMan

 

[brad]

"Silver/Gold/Platinum seem far too expensive to use for weighting purposes so Im stuck with Steel as my heaviest material. (Again I assume)"

Don't forget lead. Cheap AND heavy.
Brad

 

[metman]

BumpMan,
You say making the shorter part heavier might work better than the long lever lighter. Also you mentioned rigidity twice. Have you considered Tungsten. Its density is very close to Gold and it's Modulus of Elasticity(stiffness/rigidity) is 45 X 10^6 psi = 1.5 x iron or steel. Jesus is THE life,
Leonard

 

[BumpMan]

WOW! Im not familiar with Tungsten. Those proporties are very apealing and interesting to say the least. Its some sort of metal alloy I assume? Sounds very interesting. I will research it now. know where I can find some info on it...? Anyway Ill look into it right away and post an update. Thanks wetman.

 

[baglamas]

BumpMan,

Depending on the application of this object you may also want to consider the degree of galvanic compatibility of the two metals you will select (assuming you care about corrosion).

Is the environment corrosive? Is the piece exposed to an electrolyte? Is there an electrical connection between the two metal legs?

 

[MadMango]

You haven't really mentioned if these parts can have holes or not. You can still retain your rigidity in the long piece, but reduce the weight by adding lighting holes or cutouts.

I think tungsten carbide or Tungsten alloy A97 is widely available, and has a density around ~.600-.650 lb/in3. "The attempt and not the deed confounds us."

 

[MASSEY]

This is a fun problem.

The way I would approach it is to draw both parts in 3D separtely. Using any material, it doesn't matter at this point.

Locate the CG. Then calculate the moment based on angle from the bottom point of the Vee.

This gives force(F) x distance(X). Ultimately, this will be equal to each other.

Keep the X fixed by keeping the geometry fixed. However, if geometry is changed do so uniformly so the X to the CG does not change.

Now that the X to CG is known for each side, or leg, all that is left is to use different materials to adjust the force(F) so that that F1 x X1 = F2 x X2. X1 and X2 are known and do not change.

Adjust F1 and F2 by simply using different materials in the 3D drawing for each.

I would think that you could get very close to F1X1 = F2X2 by using different materials.

Now the fine tune can be facilitated by applying uniform coatings to the F that has to be compensated to reach equilibrium.

Fine tune coatings may be: chrome plating, powder coating, or many others, and perhaps a combination of several.

Hope this helps.

Good Luck and have fun.

 

[MASSEY]

Another thought is:

Material can be removed to facilitate getting F1 or F2 to the desired mass (density x volume) however the modifications need to be modeled in the 3D full scaled part so a new CG can be determined for the moment.

I envy you, I wish this were my problem.

 

[BumpMan]

"I envy you, I wish this were my problem."

Ha! Thanks Massey. This is kinda fun. Kinda... Dangelop, as for your concern, this object wont be in a conciderably corrosive enviornment. But coatings and the like are very inderesting approaches. All of you are genius'.