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Old 08-16-2002, 12:27 AM   #1
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Hi all,

Just wonder the screw strength for the following material:

Aluminum Aolly
Steel Aolly
Stainless Steel


Most company doesn't tell want kinda aolly they are making. So I was thinking maybe there is a standard materials (Aluminum/zinc) for screws in the RC industry for aolly materials?? So which one is stronger? Aluminum or steel aolly?

Thanks

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Old 08-16-2002, 05:57 AM   #2
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Stainless steel should be strongest for what you are talking about.....it is a steel alloy!
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Old 08-16-2002, 06:53 AM   #3
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I would rate screw strength from weakest to strongest for the same size screw as Aluminum (weakest), titanium, stainless steel, alloy steel. High tensile strength stainless steels are made for bicycle spokes for example, but they tend to be on the brittle side. I think stailess steel screws are made of softer alloys mainly for maximum corrosion resistance. Most grade 8 (high strength) screws are steel alloy that is not stainless. Then there are the super alloys like Inconel (Indium, Cobalt, Nickel) that are extremely high strength and corrosion resistant at the same time.
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Old 08-16-2002, 12:31 PM   #4
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Thanks for the feedback...

What about Duralumin?? are all aluminum screws duralumin? or is it a another aluminum aolly that is stronger then the "usual ones"???

Thanks for the feedback again~

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Old 08-16-2002, 01:09 PM   #5
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I think that Duralumin is probably a trade name for an aluminum screw. A good quality aluminum screw will be made of an alloy like T6 Aluminum alloy. This alloy is also used for the construction of aircraft parts. It is strong for aluminum but much weaker than a steel screw. Certain High Stress areas of an RC car kit should not use aluminum screws. I got greedy with Aluminum screws on the rear diff cover of My Losi XXXS. I caught a pipe with the wheel. Instead of the arm breaking, two of the Aluminum screws sheared in half causing the diff cover to rip off. One of the Aluminum screws took out the back corner of the graphite chassis while it was breaking in half. The diff cover was ruined by having a broken screw left in a blind hole. None of the expensive parts would have failed with steel screws.

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Old 08-16-2002, 01:15 PM   #6
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what about applications on the suspension blocks? or just basically mouting stuff on the chassis itself?
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Old 08-16-2002, 01:29 PM   #7
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on the Losi suspension blocks I would only run an aluminum screw on the inboard hole and leave a steel screw outboard. The shock towers are well protected and keyed to the chassis on the Losi so all four screws can be aluminum. Servo screws, Steering Post screws, front bumper mounting screws can all be aluminum on the Losi. I have actually had good luck using aluminum on the shock mount screws that go into the A-arm. Since these are under tension they don't bend easy. If you find one bent a little on your regular inspection replace it. It will wiggle as you unscrew it. Only run Aluminum screws to make minimum weight. I used Aluminum screws on the A-arm to reduce unsprung weight. Losi has a hardcoated aluminum ball again available to replace the steel ball in the shock end. You may need to polish the ball a little with 1200 grit sandpaper until it moves freely in the shock end.

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Old 08-16-2002, 01:36 PM   #8
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So put aluminum screws at places where it's well protected?

The car i'm running is Tamiya TB EvoII, I am thinking switching all the screws at the bottom of the chassis to aluminum ones. The only concern I have is that the screw in the suspension block will give if I hit any walls, since the arms and hinge pins and the suspension block are super strong on Tamiya car.
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Old 08-16-2002, 01:43 PM   #9
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I would keep the aluminum off the suspension mounts of that car if at all possible. When the screw breaks it leaves a stuck piece jammed in the block. If you are lucky you can jam a small screw driver in and back the broken piece out. If it is broken fairly smooth you have to resort to drilling which may or may not work. How much does it cost for a new block and are they available locally. What does your car weigh. Several Tamiyas at our track are underweight stock. They are the Trf 414 MII models, though.

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Old 08-16-2002, 06:42 PM   #10
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I don't know about the strength of them but I do know that steel screws are the easiest to strip at the head.
Then aluminum.
Then titanium.

If I had enough money I would change all the screws, pivot balls to titanium.

Yes, the aluminum screws always strip the thread themselves.

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Old 08-16-2002, 10:17 PM   #11
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Well,

According to Tamiya's website, M2 and EvoII weights exactly the same when stock.

I found a website called Fastener-express.com They are selling Aluminum screws cheap. That's why i'm thinking go for aluminum screws since Titanium screws are just too expensive no matter where you buy it.

Tamiya car are known to be strong, that's why i'm kinda asking around about if aluminum screws are strong enough. Besides, Aluminum screws with anodizing looks really nice.

I stripped few of those steel screws' heads, that's another reason I wanna to switch screws.

By the way, a little tip for you all for stripped screw heads or broken screw that's flat to the surface. This tip only work on the metal to metal contacts.

First use a 60 Watts+ soldering iron and place it on the top of the stripped screw or the flat surface where the screw is in. Heat it up for few mins, then quickly put a (or more to create a tip )of melted solder on top of the stripped screw or the end of the screw that's stucked in. then leave it and let it cool down completely. then use any type of clamping tool that has a rough surface, and just clamp on the tip of the solder that has cooled down and turn. if you heated the surface enough the solder should stock to the stripped screw fairly well, and then you should be able to turn the screw out of the place.

I did that to one of the bulkheads that I have on my RC car. it saved me 30 dollar+ for the bulkhead.

you might need to repeat the procedure few times. It took me a while to get the drop of solder to stick right to that tiny surface of the borken screw. but it sure worked.
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Old 08-17-2002, 08:57 AM   #12
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One of the reasons that Aluminum Screws might appear to be stronger in the head area is that I think they are made intentionally slightly undersize so that they go into a prethreaded plastic hole easy. Always install aluminum screws into a plastic hole that has run a steel screw for a while. Running the steel screw for a while will preform the threads. The steel screw will back out under some tension and then the Aluminum screw will go back in easy. Our track uses a 53 ounce lower limit for weight on touring cars without transponder module. The roar rule is 54 ounces with transponder module. I use only enough Aluminum screws to bring the car down to the 53 ounce weight.

I measured a 4-40 size socket head cap screw in blue aluminum and steel. The major diameter(point to point on the threads) of the Aluminum screw averaged about .001 inch less than the steel screw. This keeps you from breaking the screw on installation.

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Old 08-17-2002, 07:17 PM   #13
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Here are some tensile stregnths for the materials used in screws

8740 alloy steels 108,000 pounds per square inch (psi)

316 Stainless steel ( a very common stainless alloy) 70,000 psi

Titanium alloy 6Al-4V (6%aluminum, 4%vanadium) 95,000 psi (not likely to be in an RC car, more likely on your F14 tomcat)

TiSpec alloy used in climbing equipement 65,000 psi

Generic titanium (found in cheaper screws) 35,000 psi

T6 Aluminum Alloy 42,000 psi (don't know if they actually use this in RC screws, but it is a common aluminum alloy

nice site to read about the titanium used in climbing equipment
http://www.ushba.com/tifacts.html


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Old 08-17-2002, 07:47 PM   #14
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Nice information.

I wonder what kind of aluminum they use to make screws.
I also noticed that there're all sorts of aluminums are used to make rc car parts.
Some are very light and less durable but some are just slightly lighter than steel parts.
For me, titanium is the best material for the rc parts.
Light and strong.
Must for screws and drive train parts.

Only if they don't charge that much for one.
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Old 08-17-2002, 07:53 PM   #15
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I suspect the Aluminum screws are T6 aluminum. The T6 actually refers to the type of tempering used.

I agree that titanium alloy would be a better material. Titanium is hard to machine which is why it's more expensive.

Another interesting web site (fasteners for fullsize car racing) with some technical infomation.

http://titaniumfasteners.com/shop/?page=info/technical

SAE Grade 8 fasterners which are alloy steel 150,000 psi

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