Originally Posted by trax

Bob Bishop's brackets are pretty good. I've never seen a documented failure on them, at least on the newer CNC'ed versions. The UMI brackets are not engineered. Visually they are the same, but the type of metal used has different tensile / yield properties than Bishop's version which makes it an inferior product.

Originally Posted by Bob Bishop, the man...

I have made general observations on that bracket: http://web.camaross.com/forums/showthread.php?t=353703

I am not inclined to list what I see as the specific design weaknesses, as I don’t want to help them correct their design. I am always glad to help out fellow hobbyists (as most of us do), but that is on a friendly basis. UMI did not contact me and request to use my design or ask for advice in making their own. I have had others (one company and one individual who works for GM) tell me what they were planning to do, and I have offered them help and said that I would not object to their making said brackets as long as they did not associate my name with their product. The GM employee was designing brackets for his own use he said (I had no way of knowing that he was not going to produce them for sale, but I tend to trust fellow hobbyists, and no great loss if he did). He told me an interesting account of 2 sets of brackets they had fabbed up for a couple of GM’s high HP test F-bodies. On the track, they found the LS1 brakes inadequate and decided to adapt the C5 fronts. These F-bodies got LOTS of high speed miles on the track (to try to break things) and both sets of the adaptor brackets experienced problems. He submitted his personal drawings to me. I critiqued them and made a couple of suggestions. He agreed with my recommendations, thanked me, and that was the last I heard. I hope this was an accurate account. (If you are a member of this board, feel free to correct my memory) By the way, he was designing a front side adaptor, like the LG. He had seen the LG, and was concerned about a couple of issues, so he wanted to make one to do the same thing, but a stronger, less complex design.

I am not saying that UMI’s bracket is inadequate for the job, just that it is significantly weaker than my design. Those who have read my posts in the past know that when it comes to safety margins, I believe that if some is good, then more is better, and too much is just right.

For normal street driving where there will be no exposure to salted roads, that bracket may be OK. For track use, OR where they may be exposed to corrosive elements, I would not feel comfortable. I do not know if the bracket is powder coated, but I would never put any of the more heat sensitive aluminum alloys through the heat of normal powder coating. I have mentioned in the past, a well known aftermarket forged-center wheel manufacturer told me of catastrophic wheel failure he experienced after powder coating a set of new wheels a third time (customer was picky about the exact shade). He said the oven was regulated to 350* F. The metallurgist at Kaiser who helped me so much, strongly discouraged me from powder coating my parts, especially if I was going to use one of their higher strength alloys (they are more susceptible to heat accelerated fatigue).

Originally Posted by UMI Performance

I understand your concerns and like I said I will be glad to express my ideas and work. If you laid each bracket side by side I see no reasons to pick one, Bob has made a tremendous product from what I have read and seen, there is no reason to compare since they are both well made items. I did not produce these brackets to compete with Bob or make a better product then he has. I did this to supply a product that was no longer being manufactured or available. I did this with intentions for others to continue to do this upgrade, especially the LT1 based models seeing there is no item like this available to date. I too take safety very serious and that is #1 one of my list, that is one reason you will find my items to be overkill for the applications they are intended for.

Currently we have tested the brackets using our own ability, hard driving and in shop procedures we put our products through. To be honest I have not yet stressed tested the brackets as Bob has, but I will and I am going to. I will do this so the facts can be posted for consumers to see. This will also take care of concerns you may have, having this completed is no problem and I will do so. The reason I have not yet done this is material I have chosen to use for this particular bracket. We used Aluminum grade 2024 T3511 (Not T6511 like I posted before, that was a typo). This grade of material has much higher tensile and yield strength as well as higher percent elongation then 6061 that others have choose to use for similar items. Below I will post #’s of research I have done before production of this item. Our material is supplied with test reports where this information was taken from. At the time of purchasing I compared each strength areas of the different materials (6061 and 2024) and I will post it below.

Aluminum 6061 T6511- Extruded
Tensile Strength- 38,000 psi
Yield Strength- 35,000 psi
Elongation- 11.1/11.4 %

Aluminum 2024 T3511- Extruded (Material my bracket uses)
Tensile Strength- 68,000 psi
Yield Strength- 48,000 psi
Elongation- 12%

As you can see 2024 has almost double the tensile and yield strength as 6061. Price for this material at the time I purchased it was just a little more then double the price of 6061.

Yield Strength:

Yield strength, or the yield point, is defined in engineering as the amount of strain that a material can undergo before moving from elastic deformation into plastic deformation. Elastic deformation is spring-like deformation, where a material will return to its original shape. The stress felt by a material given a certain strain is defined by linear relationship, with a slope defined by Young's_modulus. If too much strain is applied, the material will deform permanently, or plastically. The yield point is often defined, due to the lack of a clear border between the elastic and plastic regions, by a .2% offset from the linear region. The point where this offset line intersects the stress-strain curve is yield point. (Not my wording)

Tensile Strength:

The resistance of a material to a force tending to tear it apart, measured as the maximum tension the material can withstand without tearing. (Not my wording)

I do not have any fancy numbers or statistics on why I have chosen to use powder coat over anodize. We have found powder coat to be a much more durable coating to resist road debris, chipping, salt and corrosion. We have found anodize to fade easier under continuous amounts of sun light, although this won't be a large factor on this product. Anodize requires approx. a 200 degree dipping tank for the coating process, very close to the same temperature and process time of the powder coating process. Having the brackets powder coated also cost us twice as much as anodize, so cost wasn’t the reason. Powder coat is our preference, you will find that 95% of suspension components our powder coated as well.

Hope that helps,
Ryan

Originally Posted by Bob Bishop

I will give you one example of a potential problem I see with your brackets. I have not mentioned this or referred to it elsewhere, as it is less troublesome to me than other choices you have made. It is your alloy choice.

You post properties for virgin material. Have you seen stress life data curves or fatigue life cycles charts on 2024? Even in an over-aged temper it looses more of its original tensile and yield properties than any other high-strength aluminum I have researched. And that is at ambient temperature. When the testing temperature is elevated, it looses a MUCH higher % of its strength than 6061. At a point in the life cycle testing, the curves cross and the 6061 is now stronger. I have stress life data curves provided by Westmoreland Mechanical Testing & Research. Depending on the shape of the test sample and application of test forces, some of the results are shocking, but all of them are at least troubling. In worst case, the 2024 test sample had lost about 75% of its original strength, and that was at ROOM TEMPERATURE testing! This potential loss of strength MUST be taken into account in the engineering stage.

If you are not familiar with this type of test, the sample is continually stressed short of yield. As the test cycles accumulate, the stress levels are lowered appropriately to ensure that the material is never stressed to yield. Again, that is keeping short of yield; not approaching UTS. After only 20,000 cycles the 2024 was already under 30,000 psi (calculated), at AMBIENT temperature. When these tests are performed at elevated temps things get really scary. I have results showing 2024 loosing about 85% of its original strength at the end of the life cycle test when performed at 300* F.

After giving my metallurgist the worst case temperature that the brackets would reach on the race track (hard data accumulated from actual track testing), he suggested using 6061 and simply beefing up the bracket and lab testing again (his was the second professional recommendation I received to do that). And he was in charge of Kaiser’s 7068 project. He really wanted me to use the 7068 initially, until I was able to give him the data on maximum temps. That is (was?) Kaiser’s strongest, newest aluminum alloy: 100,700 psi Ultimate Tensile and 93,600 psi Tensile Yield. He had even offered to get me two 12’ bars to perform sample runs, until he determined that the alloy was not appropriate for my application. Of course, they manufacture 2024, 7075, and other high-strength alloys as well, but he recommended against their use also, as their initial strength and remaining strength after fatigue life cycle testing were both inferior to 7068. The 7068 also has a greater % property loss from a high heat environment than 6061. During the months I was researching alloys, the price of the 7068 kept escalating, but before strength concerns arose, I was committed to use it even when it cost about 15% more than 7075 (and more than 2024).

Then there is the problem of corrosion. 2024 is far inferior to 6061 in corrosion resistance. And even more so in the T3 temper you have selected. Please explain why you choose that temper (if you want to continue this; I don’t). The 2024 needs protection from the environment. Powder coating will provide protection as long as it is not violated. When you torque down the 14mm bolts to 120 – 140 lbs/ft, there is a good chance that the powder coat will crack at the bolt or washer edge. Then you have no protection for the corrosion prone 2024, and even worse, this is an area of high stress.

I choose clear HARD COAT anodizing after doing research and getting professional advice on the subject. The anodize is not just an exterior coating. It penetrates as deeply under (into) the metal surface as it builds up thickness on the top of the surface. It further increases abrasion resistance and measurably increases surface hardness. And in any case, 6061 is naturally very corrosion resistant, even without anodizing. 6061 is more environmentally stable (corrosion resistant), more temperature stable (weakens less from heat), and long term stress strength stable than 2024. In the correct environment and application, virgin 2024 is obviously stronger, but do you know how many years someone may leave these brackets on their car, or how hard they will be used? What if your customer has no intention of using his car on a track, but later sells the car to someone who turns it into a track car?

Again, I am willing to establish a positive relationship with you. I do not appreciate someone implying that I cheaped-out on the selection of materials for my brackets. I am a member of this board for enjoyment. From your first post, I thought that was possibly your intention also.

Bob

Originally Posted by regorih355

some one is going to be sorry when i finish masterbating
Roger

Originally Posted by Snow Dog

i agree that if the 2024 is perfectly fine then anything beyond it is overkill. but do you want to be the person with a 2024 bracket that fails?