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Old 10-11-2012, 12:03 PM   #1
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Default Aluminium bulkheads vs Plastic

All the new cars.. the Serpent, Shepherd, Capricorn have gone with aluminium bulk heads instead of plastic, Xray have stuck with the plastic ones on the NT1.

What's the advantage/disadvantage of both?
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Old 10-11-2012, 01:15 PM   #2
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All the new cars.. the Serpent, Shepherd, Capricorn have gone with aluminium bulk heads instead of plastic, Xray have stuck with the plastic ones on the NT1.

What's the advantage/disadvantage of both?
Once its all put together its a much stronger assembly, allowing the suspension to do its work better. Plus the fact that with todays technology its cheaper to machine the parts out of bar stock than to make a plastic injection mold.
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Old 10-11-2012, 01:25 PM   #3
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I've seen several racers get away from the plastic housings because their 'braking habits' caused the metal parts to become embedded into the plastic. It's not pretty when it takes you out of contention. There are other 'tweaks' you can do to space out the 'hot parts' but aluminum housing replacements are the logical 'manufacturer' action.......sounds like the builders are getting practical input.
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Old 10-11-2012, 02:17 PM   #4
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Once its all put together its a much stronger assembly, allowing the suspension to do its work better. Plus the fact that with todays technology its cheaper to machine the parts out of bar stock than to make a plastic injection mold.
Funny, if it is made stiffer for a better work of the suspension why have all curent cars a complete flex system?
Bad thing of aluminium parts is that it will bend causing tweak. I have seen people changing the aluminium bulkheads several times..

I am not sure if it is cheaper... Making a good mold for plastics is indeed expensive but milling a complex 3D item as the Serpent gear shaft blocks does also cost some material and machine time. The more simple designs from Shepherd an Mugen can be directly milled or cutted from a plate of aluminium.
The only difference between plastics and aluminium is that with aluminium it is much easier to make direct changes or create some different models to test with. On the other hand current 3D platic printers can do the same with plastics
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Old 10-11-2012, 06:48 PM   #5
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The aluminum bulkheads are worse than the plastic because you can get alot of problems with bent bulkheads at least with plastic there good or there broke and it's less work with plastic because when you have wreck were you break an arm you should tear the car down to the bulkheads to check and see if it's bent
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Old 10-11-2012, 07:33 PM   #6
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I feel like the plastic is better because of what one of the other guys mentioned. tweak! you have to watch for it with aluminum bulkheads, even though i have yet to have this issue. I sure love the look of that aluminum on my MTX5!
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Old 10-11-2012, 08:21 PM   #7
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I prefer plastic as its easier to keep screws in and less likely to suffer from heat transfer.
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Old 10-11-2012, 09:18 PM   #8
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Funny, if it is made stiffer for a better work of the suspension why have all curent cars a complete flex system?
Bad thing of aluminium parts is that it will bend causing tweak. I have seen people changing the aluminium bulkheads several times..
I currently drive the first car I have ever owned with aluminum bulkheads. I too had concerns about bent/tweaked parts with use. But while assembling and repairing the car after a couple of crashes, I am begining to think this is a minor issue at best. When all the bulkheads are assembled to the chassis and tied together with other kit components it becomes an extremely rigid almost one piece like structure that will take a kit replacement type crash to bend any of it. It seems as though the kit is designed to shear off plastic parts to save the aluminum ones.....at least that has been my experience so far with the car
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Old 10-11-2012, 09:19 PM   #9
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I like the plastic because it's just so much cheaper. I think I'm paying six bucks a set and only replaced one bulkhead all year anyways. I can't speak to the aluminum because I don't have it, but then again, I'm only paying 300 for the whole kit. I'd probably try aluminum were it offered on my car, just so I'd know for myself if there is any kind of difference, but I'm not unhappy with how it is now.
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Old 10-12-2012, 08:45 PM   #10
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Thinking about it more, i think if Xray saw it as necessary they would have gone that way with the RX8 seeing it was released aot later then the NT1.
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Old 10-12-2012, 10:11 PM   #11
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Originally Posted by Roelof View Post
Funny, if it is made stiffer for a better work of the suspension why have all curent cars a complete flex system?
Bad thing of aluminium parts is that it will bend causing tweak. I have seen people changing the aluminium bulkheads several times..

I am not sure if it is cheaper... Making a good mold for plastics is indeed expensive but milling a complex 3D item as the Serpent gear shaft blocks does also cost some material and machine time. The more simple designs from Shepherd an Mugen can be directly milled or cutted from a plate of aluminium.
The only difference between plastics and aluminium is that with aluminium it is much easier to make direct changes or create some different models to test with. On the other hand current 3D platic printers can do the same with plastics
With a mold, you have to worry about your return on investment. A mold is very expensive, but it will allow you to make a ton of parts very cheap that can be sold for very cheap. You also have to worry about molds getting damaged/wearing out and having to pay to repair them. What happens when the design changes slightly? Does a new expensive mold need to be created? With complex parts you get complex molds. Also with plastic parts, you need to worry about your material. Is the material quality consistent? Is the finished product consistent from batch to batch of material. Does the plastic properties change in different conditions (hot/cold)? Is the price of the raw plastic pellets going to change as oil prices go up and down? Finally what happens to the mold when the part is obsolete? Will it end up as a paperweight collecting dust on some shelf.

With cars these days going to mostly aluminum and carbon, it allows the companies to pass material AND machining costs to the consumer. The investment into the CNC machine will get you a lot further than a plastic mold. The CNC machine can be programmed to machine anything. Cycle times maybe a bit longer than a plastic part, but you can just pass that cost to the consumer. You don't have to worry about the material quality except for ensuring its the correct grade. Design change? No problem, just load the new machine path into the CNC and you're off making new design parts. Need the volume of parts that you can easily get from injection molding? No problem, farm all the CNC work to China where they have factories filled with CNC's.

3D printers are amazing, but I believe they are still too expensive for mass producing parts. They are very useful for creating complex prototype parts used for testing, but those parts usually turn into injection molded parts.
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Old 10-13-2012, 12:54 AM   #12
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So the general jist is plastic is superior if the design is right first time, but it's more expensive to toolup for and very expensive to change designs.

Aluminium is easier to prototype and cheaper to tool up for the manufacturer but ends up costing more for me.

The rigidity issue is moot for me, the NT1 generates traction fine as does the 747.
But I can replace my bulkheads cheaper on the NT1.
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Old 10-13-2012, 04:06 AM   #13
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Although Xray has stated in their column about the RX8 they do believe plastic is the way it would not supprise me that a next generation cars will get aluminium too. Until that time I think they will have some extra market with users who fear aluminium.
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Old 10-13-2012, 06:01 AM   #14
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I've only had one aluminum part get bent on the Shepherd 1/8th, the rear suspension front lower pin mount. It was easy to notice that it was bent because the hinge pin didn't line up any more. And it was not expensive to replace, it's only like $12 or something. I have never had or seen a bulkhead get bent.
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Old 10-13-2012, 09:59 AM   #15
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Although Xray has stated in their column about the RX8 they do believe plastic is the way it would not supprise me that a next generation cars will get aluminium too. Until that time I think they will have some extra market with users who fear aluminium.
I think Xray may do all their plastic molding in-house with their specially formulated plastic. If that's the case, their investment into plastic is huge.
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