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Old 08-31-2012, 03:55 PM   #751
Gros Buck
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Quote:
Originally Posted by Yellow Pig View Post
Interesting.

Could you elaborate on why you switched from aluminum to HDPE?
I'm seriously asking myself too. There is no selling point on using HDPE besides cosmetic. Mecanicaly speaking, it's questionable.

This thing is a job for 6061 T6. You want it white ??? then have it powder coated white ...

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Old 08-31-2012, 04:02 PM   #752
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Originally Posted by Gros Buck View Post
I'm seriously asking myself too. There is no selling point on using HDPE besides cosmetic. Mecanicaly speaking, it's questionable.

This thing is a job for 6061 T6. You want it white ??? then have it powder coated white ...

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Old 08-31-2012, 04:20 PM   #753
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thoughts re materials.

Heres a quick blurb from the web in regards to HDPE and Acetal (which is similar to Delrin)

Key Benefits of HDPE Sheet and HMWPE Sheet:

Very low co-efficient of friction
Very high surface release properties
High chemical resistance
Excellent impact resistance
Very good damping properties
Weldable plastic
Excellent abrasion resistance

Acetal is the product oggy knobs are made from, pretty strong stuff.

Applications of Acetal Machined Parts:
Precision gears
Bearings with close tolerances
Electrical engineering insulators
Compact bearing assembly
Snap fit assemblies
Parts which operate in water between 60 to 90;C

I'd think they could both have great uses with nav towers. Great to see people using it.
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Old 08-31-2012, 04:22 PM   #754
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In a crash situation I'd think HDPE/Delrin etc would result in a better outcome for the rider? But who wants to put there hand up to test it
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Old 08-31-2012, 04:23 PM   #755
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Originally Posted by theantipaul View Post
More out of curiosity then anything else, I figured what the heck.



Seems very rigid vertically and gives nicely side to side. Taking it for a ride this afternoon.
look forward to your thoughts.
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Old 08-31-2012, 04:58 PM   #756
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Originally Posted by crankshaft View Post
What's the French word for innovate?
Serioulsy PSI of HDPE is nothing (5K PSI ???). You can barely make filets out of it. Forget about Heli-Coils. PSI/lbs is pretty low compared to 7075T6 or better 7068T6 (100KPSI+). Number of cycles for 7075T6 at 25000 PSI load is more then 500,000,000 cycles. Which is many orders of magnitude higher then HDPE.

I see a good looking device. But in this case, "Innovation" is a word that one would hear from the marketing departement. Not from the engineering dpartment.

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In a crash situation I'd think HDPE/Delrin etc would result in a better outcome for the rider? But who wants to put there hand up to test it
Me.

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Gros Buck screwed with this post 08-31-2012 at 05:08 PM
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Old 08-31-2012, 05:12 PM   #757
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I don't know how all those numbers translate to real world use, so I'll defer to the guy that's actually willing to try something new and test it out. Typical engineer, always running to what they know and running away from anything new. Show us your nav tower
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Old 08-31-2012, 05:15 PM   #758
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Quote:
Originally Posted by Gros Buck View Post
Serioulsy PSI of HPDE is nothing (5K PSI ???). You can barely make filets out of it. Forget about Heli-Coils. PSI/lbs is pretty low compared to 7075T6 or better 7068T6 (100KPSI+). Number of cycles at 25000 PSI load is more then 500,000,000. Which is many orders of magnitude higher then this plastic.

I see a good looking device. But in this case, "Inovation" is a word that one would hear from the marketing departement.



Me.

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I think you are making too many assumptions about the Design. The weight of the system is being supported by a massive chunk of 6061. For these plates to encounter the forces you are talking about they would have had to suffered a massive impact. None of the nav equipment would survive, forget the rider. The deflection that the HDPE would offer might save the nav equipment in a crash.
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Old 08-31-2012, 05:17 PM   #759
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Originally Posted by cross-country View Post
I think you are making too many assumptions about the Design. The weight of the system is being supported by a massive chunk of 6061. For these plates to encounter the forces you are talking about they would have had to suffered a massive impact. None of the nav equipment would survive, forget the rider. The deflection that the HDPE would offer might save the nav equipment in a crash.
It still has the top backbone bolted to the top triple was my guess right?
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Old 08-31-2012, 05:29 PM   #760
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It still has the top backbone bolted to the top triple was my guess right?
It looks like it. You can see it the the top picture I think. The backbone is robust, to say the least. If I break that part in a crash I really don't care what happens the rest of the bike, I just hope the helicopter that is coming to pick me up is in good shape.
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Old 08-31-2012, 06:11 PM   #761
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Originally Posted by cross-country View Post
I think you are making too many assumptions about the Design. The weight of the system is being supported by a massive chunk of 6061. For these plates to encounter the forces you are talking about they would have had to suffered a massive impact. None of the nav equipment would survive, forget the rider. The deflection that the HDPE would offer might save the nav equipment in a crash.
Ok

Let's ask the question the other way around ... Why one would want to built it in HDPE knowing, it has 20 times less PSI then 7075, far less Heat resistance, Far less cycle life, much heavier Density to strength ratio ??? Knowing as well the HDPE is never used in structures unless the most critical parameter is chemical resistance or very low friction ??? It is also known that HDPE "dries" rapidly under UV and consequently, structural properties are affected adversly.

HDPE is a bushin (plain bearing) or glide material ....

Why not makin that tower it in paper then ??? HDPE in that case is an exercise of style !!! a square wheel !!!

By the way, I've been playing with that material for decades. I've built HDPE reservoirs (yes a structure !!! ) for abrasion resistance.

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Old 08-31-2012, 06:50 PM   #762
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Originally Posted by cross-country View Post
It looks like it. You can see it the the top picture I think. The backbone is robust, to say the least. If I break that part in a crash I really don't care what happens the rest of the bike, I just hope the helicopter that is coming to pick me up is in good shape.
Yea, no doubt. If someone is breaking into my house, it's the first thing I'm grabbing Nav tower by day, home defense at night!
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Old 08-31-2012, 07:56 PM   #763
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??? !!! !!!

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Every good thread needs a loudmouth, know-it-all prick.
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Old 08-31-2012, 08:11 PM   #764
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Every good thread needs a loudmouth, know-it-all prick.
That he's named Paul, and is slagging theantipaul, is perfect.
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Old 08-31-2012, 08:20 PM   #765
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So because some one has shared there knowledge about something he clearly knows a lot about that means he's a loud mouth know it all prick does it?


I use ally and hpde a fair bit in my work and I'm not sure if hpde will work I was thinking it might but I'm willing to listen to all arguments.
I like the idea of hpde because it will move in a crash (and hopefully bounce back) it should also absorb a lot of high frequency vibration but I'm not sure how it will go when it comes to bolting/clamping it.
I've seen plenty of hpde sheet split from the pressure of a bolt and washer clamping down on to it.
Maybe using more bolts with top hat collars or maybe using rubber grommets could solve that issue.

Also I think black might be a better color to use for uv resistance.
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