Rallye navigation bracket photo thread - Page 51

Gros Buck · 08-31-2012, 03:55 PM

Quote:

Originally Posted by Yellow Pig

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 ...

Paul Jr

crankshaft · 08-31-2012, 04:02 PM

Quote:

Originally Posted by Gros Buck

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 ...

Paul Jr

What's the French word for innovate?

tileman · 08-31-2012, 04:20 PM

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.

tileman · 08-31-2012, 04:22 PM

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

tileman · 08-31-2012, 04:23 PM

Quote:

Originally Posted by theantipaul

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.

Gros Buck · 08-31-2012, 04:58 PM

Quote:

Originally Posted by crankshaft

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.

Quote:

Originally Posted by tileman

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.

Paul Jr 8

crankshaft · 08-31-2012, 05:12 PM

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

cross-country · 08-31-2012, 05:15 PM

Quote:

Originally Posted by Gros Buck

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.

Paul Jr 8

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.

crankshaft · 08-31-2012, 05:17 PM

Quote:

Originally Posted by cross-country

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?

cross-country · 08-31-2012, 05:29 PM

Quote:

Originally Posted by crankshaft

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.

Gros Buck · 08-31-2012, 06:11 PM

Quote:

Originally Posted by cross-country

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.

Paul Jr 8

crankshaft · 08-31-2012, 06:50 PM

Quote:

Originally Posted by cross-country

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!

cross-country · 08-31-2012, 07:56 PM

Quote:

Originally Posted by Gros Buck

??? !!! !!!

Paul Jr 8

Every good thread needs a loudmouth, know-it-all prick.

Luke · 08-31-2012, 08:11 PM

Quote:

Originally Posted by cross-country

Every good thread needs a loudmouth, know-it-all prick.

That he's named Paul, and is slagging theantipaul, is perfect.

DRjoe · 08-31-2012, 08:20 PM

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.

08-31-2012, 04:20 PM	#753
tileman Studly Adventurer Joined: Mar 2007 Location: Melbourne, OZ Oddometer: 730	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. __________________ If ignorance is bliss, why aren´t more people happy?????

08-31-2012, 04:22 PM	#754
tileman Studly Adventurer Joined: Mar 2007 Location: Melbourne, OZ Oddometer: 730	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 __________________ If ignorance is bliss, why aren´t more people happy?????

08-31-2012, 05:12 PM	#757
crankshaft Guns are for pussies Joined: Aug 2004 Location: Burlingtron,VT Oddometer: 13,783	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 __________________ Just say'IN

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08-31-2012, 08:20 PM	#765
DRjoe Beastly Adventurer Joined: Sep 2007 Location: Sunshine coast qld Oddometer: 4,251	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.