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Old 08-31-2012, 08:28 PM   #766
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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?
Sometimes it's not what you say but how you say it.
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Old 08-31-2012, 08:33 PM   #767
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In a crash situation I'd think HDPE/Delrin etc would result in a better outcome for the rider?
The Delrin I've used can crack and break, resulting in sharp edges. That could be worse than aluminum, especially on the nav tower. HDPE won't do that, unless it sits in direct sunlight for 5 or 10 years.

I like the idea of the flexibility of HDPE in this application. It will flex a bit or a lot in a crash, and bounce right back, or nearly right back. To me, that's the value of using HDPE here. Aluminum will bend, maybe a lot, resulting in a permanently twisted nav setup.

My concern with HDPE in this application would be where are all fasteners are. Without super wide washers everywhere, the holes and the material around the holes may well mush out, allowing everything to loosen up.

I used a LOT of HDPE on my Dakar bike (probably 15 pounds of it), though not on the nav tower. In the right places, it works very well, even in some high stress locations. One location gets a 200+ pound load on it occasionally, and it's been rock solid.
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Old 08-31-2012, 10:12 PM   #768
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Wow you guys have been busy, thanks for the support, first off I was interested in Tilemans concept of using HDPE, I've worked with it before and made molds for it but never use it for a structural part.

Nav towers place a lot of valuble gear in what could be very vulnerable places, $300 to $500 roadbook holders, 2 Squadron LED lights @ $330ea, computers, repeaters, all bolted up rigidly to aluminum plates, you go down and the more rigid the mounts the more impact taken by the pricey gear. That's the motivation.

I wanted to test the concept for myself using HDPE just for the side plates, I wasn't worried about front or top impacts, if you do that you've had a bad day and you start over, but side impacts with HDPE and the gear can move, instead of crush or bend and spring right back. That's what I thought Tileman was presenting and after building it and riding with it today I think it has value, and little in the way of drawbacks.



Is HDPE strong, no. Is it strong enough in this application, I think yes.

With fender and tooth lock washers, strict torque values and locktite, I wouldn't be concerned with fasteners, vertically in this application I think the HDPE worked as well as aluminum. Delrin has some nice properties, but it really does have the nasty ability to shatter on impact. HDPE? well?



With HDPE side plates I think the gear will be more survivable in a side impact.

So I'd say Tileman is on to something here. Might not be for everyone, but I'm going to look at it more.
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Old 08-31-2012, 10:23 PM   #769
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Awsome work.. I would use it!

Quote:
Originally Posted by HogWild View Post

My concern with HDPE in this application would be where are all fasteners are. Without super wide washers everywhere, the holes and the material around the holes may well mush out, allowing everything to loosen up.
thru bolts with collars?
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Old 08-31-2012, 10:48 PM   #770
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Originally Posted by theantipaul View Post
Is HDPE strong, no. Is it strong enough in this application, I think yes.

With HDPE side plates I think the gear will be more survivable in a side impact.

Might not be for everyone, but I'm going to look at it more.
+1 great job anti

The reason I mentioned this a few pages back was partly in response to the comment about the placement of equipment (the picture of Jonah's setup) is sometimes placed in a pretty sketchy place. Were a rider to crash and hit the nav equipment my thought was that a HDPE style tower would be better.

Ok, some thoughts.

Is it more resistant to vibration, I believe so.

For me, is it easier to work with in my shed, yes.

Hence is it easier for me to prototype parts, yes.

Can I get it for free, yes (in small sizes but thats enough). Alloy, no chance. (but if someone in Melbourne can let me know where, happy to be proven wrong on this).

I had heard of the problem with UV, and considering I'm based in Australia UV is an issue but after talking to the supplier (where I grab stuff out of their off-cuts bin) he didn't believe it was really an issue and he seemed to have a reasonable idea about what I was planning on using it for. Hence I accepted his knowledge about it.

I'm honestly stoked that someone with more resources than me has made one . I reckon it looks great and from their first ride seems to function well.

If in the end it doesn't work out then I'll just use it to prototype parts.

I reckon its a great way to go, I'll be doing something similar. (when to 2 projects I have are done-ish) hehe
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Old 08-31-2012, 11:53 PM   #771
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That looks great Paul, and can see how that might save some expensive parts in certain types of crashes. But if you're trying to protect riders (tileman), first thing I'd want to do is reorient the supporting members so they'd would be more likely to give on impact (from the top down). Think that kind of redesign would be a much bigger improvement than simply switching materials.

*Not talking about Paul's setup specificall, just commenting on rally nav bracketry in general.
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Old 09-01-2012, 12:25 AM   #772
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Sometimes it's not what you say but how you say it.
I see your point
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Old 09-01-2012, 02:28 AM   #773
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I think the point here in using HDPE is the survival of the whole tower in an impact that would cause either the tower to bend or the navigation equipment to break.
Prototyping aside (HDPE as earlier said is easy to work with) one can make the aluminium tower in such a way that it would break in certain, replacable joints in a heavy impact. But you have to ask yourself if you want to go through the designing process of such a thing. If aluminium bends, for the professional rider, it may or may not cause a problem as in the next bivouac he will have the chance to choose between a googlion of nav towers.

Safetywise, I would prefer to have a design that is good. Material is irrelevant in this case, as HDPE if the design is wrong will damage you in an accident. So from this point of view as an engineer I would not go to HDPE for that and only for that reason. There are many other reasons described above which make it an attractive material and if it is used in conjuction with other materials then may be the user can get the best of both worlds.

As far as the UV problem, I have installed d1000 HDPE pipes and they are still there, biogas pipes are mainly HDPE, water pipes are mainly HDPE etc. I would worry about other things first than UV protection. You can go and buy black HDPE which contains carbon black and you will be ok for the rest of the bike's life.

Mechanically speaking, nobody said that HDPE has higher Young's Modulus than Aluminium, load to weight ratio etc... But you have you always have to ask yourself what you need in any given design. The sentence ''nobody has done it before'' or ''they are not using this material for this type of design'' proves nothing to me and I am an Engineer... Let alone if you are not one and you are just a member who reads these two sentences . Check the plastic bash plates. They are there for a reason. Check the CF bash plates. They exist too . Aluminium tanks vs Plastic tanks etc ... ... Some you win some you loose

To get back in two the Nav Tower subject, I think a combination in the right places of HDPE, Aluminium and may be CF would be the best. Aluminium could be used where the assembly needs to be stiff (the head part for example), HDPE in the joints or other stressed members in a crash in order for them to give a bit of room in the unlikely event . Carefully designing such a thing would be a great success in my opinion. Especially if the ''break away'' parts can be replaced very fast as nobody wants to sit there forever after a crash replacing parts in ther navigation tower.

I think the problem, if you are not the one with the right equipment in your hands, are the suppliers. You have to find somebody to do the HDPE, the Aluminium and the CF. Even Aluminium may need two or three suppliers to get it right (at least here in Greece ) and that, may prevent some people from using more than one material. Dont forget that TheAntiPaul had already a good design and just changed the material. And this specific design happens to be flat plates. That is a very good example of a simple and good design as you can just buy yourself the HDPE sheet and cut it, drill it and off you go... Complex designs are more difficult to perfect and if looks is what you want then I dont think you can make HDPE welds and bends that look half as good as an anodised aluminium part or a CF part...
But then again if you want good looks you go to a hair salon

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Old 09-01-2012, 04:05 AM   #774
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Quote:
Originally Posted by HogWild View Post
I like the idea of the flexibility of HDPE in this application. It will flex a bit or a lot in a crash, and bounce right back, or nearly right back. To me, that's the value of using HDPE here. Aluminum will bend, maybe a lot, resulting in a permanently twisted nav setup.
It's buried somewhere in the back of this thread, but a spaniard named Paco Martinez rode a Kawasaki to the finish of the 2012 Dakar with a very ugly nav tower entirely made of HDPE and steel threaded rod. He used HDPE also on the skid plate and fairing brackets.

Found it: http://www.advrider.com/forums/showp...&postcount=136
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Old 09-01-2012, 07:04 AM   #775
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Nice work Paul. What thickness HDPE did you end up running with? Thick enough, too thick, rigid enough?
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Old 09-01-2012, 07:24 AM   #776
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But if you're trying to protect riders (tileman), first thing I'd want to do is reorient the supporting members so they'd would be more likely to give on impact (from the top down). Think that kind of redesign would be a much bigger improvement than simply switching materials.
Design is almost always a compromise of priorites, I haven't come up with an elegant solution for keeping everything simple, small, light, strong and tight to the bars, survivable, easily replacable and completely safe for rider and gear. But the beauty of this thread for me is sharing the info and building on it.

Quote:
Originally Posted by 640 Armageddon View Post
Mechanically speaking, nobody said that HDPE has higher Young's Modulus than Aluminium, load to weight ratio etc... But you have you always have to ask yourself what you need in any given design. The sentence ''nobody has done it before'' or ''they are not using this material for this type of design'' proves nothing to me and I am an Engineer... Let alone if you are not one and you are just a member who reads these two sentences
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Nice work Paul. What thickness HDPE did you end up running with? Thick enough, too thick, rigid enough?
This was my thought exactlly, this application does not demand a higher Young's, my aluminum side plates are 3/16" thick, I did make them out of 1/8" to try, they were too flimsy in my opinion, my concern was impacts as well as vibration and fatique. The HDPE side plates are 1/4" and the lowers are 3/16". The design inherently supports verticle loads, the concerns of vibration and fatique go away with HDPE, to the extent that the feet that attach the side plates to the lower triple might be totally unnecessary. On the aluminum versions the feet are only to mitigate vibration, the loads are taken by the plate sandwiched between the lower handlebar clamps and the upper triple.

I had a design that lent itself to testing this concept easily in such a way that it appealed to me. It actually works for me and I'll be leaving it on the bike till something I see as better comes along. It's not perfect, tweaking here and there is what testing is all about, but I think it has enough promise at this time to continue down this road. This was prompted by the thoughts from this thread! I would have not come up with it, let's keep it going.
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Old 09-01-2012, 07:48 AM   #777
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This thread really is amazing, lots of smart folks adding opinions and designs. It's amazing what can be done when people share a common desire!
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Old 09-01-2012, 09:53 AM   #778
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Incase you guys didn't know, the above is a video Paul, you should dub in "Beat it" by Michael Jackson
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Old 09-01-2012, 11:35 AM   #779
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Originally Posted by theantipaul View Post
Design is almost always a compromise of priorites, I haven't come up with an elegant solution for keeping everything simple, small, light, strong and tight to the bars, survivable, easily replacable and completely safe for rider and gear. But the beauty of this thread for me is sharing the info and building on it.
Oh, but you have come up with a really elegant solution. Think that's a great setup.
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Old 09-01-2012, 04:14 PM   #780
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Seeing how safety is a big concern I use to make sheer bolts for our guillotine very simple to do just machine down a bolt in the middle with a v shape al thou we did not strain test them when ever some made a mistake cutting aluminum printing plates the bolt broke saving the machine , we could use this simple idea and aply it to our bikes I would also teather the
Tower as you don't want a scud missile smashing you as well .
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