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Discussion Starter #1
This is an open question for anyone who knows any part of the answer.

Many parts can be replaced by better, lighter parts such as CF and Titanium. The difference between some of these materials and steel is fairly well noted.
Al is about 30% of steel and Titanium is 40% of steel. I am looking for these kind of comparisons between Al and CF and the other materials. In some cases CF can replace Al (such as heal guards or shift leavers) so a comparison of materials densities would be useful.
One could then make better decisions based on what you get for what you pay. One could build the ultimate featherweight bike if you throw out enough cash but haw many dollars per gram are you going to spend and when is enough enough, based on the amount gained and the dollars paid.
 

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There are quite a few more elements to factor in besides simply material density. If you have a specific question about a specific part, it would be helpful.
 

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MR. Twill
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33 580 18.3 322 1.8 .065
20.3 275 13.1 178 1.54 .056
10 36 3.7 13.3 2.71 .095
15 170 3.25 36 4.62 .162
30 122 3.8 15.6 7.82 .274
18 400 12.5 278 1.44 .052
9.8 190 7.5 146 1.30 .048
10.5 500 4.1 197 2.54 .092
6.5 257 3.25 129 1.99 .072
12.5 665 5 267 2.49 .090
7.7 342 4 175 1.95 .071
 

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Chilehead
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what's heavier, a ton of feathers or a ton of gold?
While they both have the same mass, they do not necessarily have the same weight (heavy implies weight, not mass).

Generally, the gold would be slightly heavier as it's cg would be closer to the cg of the earth (or whatever reference you are using), unless the feathers were distributed in such a way to have a lower cg than the gold, which is highly unlikely.

This assumes of course that both are weighed in the same place.

Tom
 

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Discussion Starter #11
Also this quote: "If you have a specific question about a specific part, it would be helpful."

I am interested in many parts, from the plastic gas tank to the steel tube frame used to hold the lights, instruments and fairing. I started to read the hal.archive and think it may be usefull but it will take time. College and Physics classes were some time ago. I find the "Materials selection chart" a fascinating thing (when was that created, if anyone knows?).

I was hoping for some rule of thumb info. but may not be so lucky.

As for a specific part, lets use the steel tube frame that holds the lights, instruments and fairing. I think this could be made of many things and CF tube or Al tube welded together are on the list. I think CF could be made in a smaller dia and thus lighter format but this is only guess work. The frame work is, at present, steel with joints connected with screws or bolts and this could be changed, at least in part. I know this could be a complicated engineering design if one wants to get into it. To make it out of Al would be relativly simple as I could do most of the work myself. CF is more difficult as it is something I would need to learn. But I have some crazy shortcut ideas (mostly from lack of ANY experience) like using CF fishing rod tubes or golf club shafts.
This is what it looks like:
 

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you can purchase carbon tubes but it's how you joint them and how you coat them (if you care about UV and such). but judging from the bike pic why even go through the trouble? you wont feel any difference when you ride and 99% certain if you did a track day.

i think a ton of CF is weighed not only in terms of weight in this case but as a function of you and your bike performance x application.

take out that square light alone and you've exceeded CF and TI and any other material in making up the front end weight :p
 

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Also this quote: "If you have a specific question about a specific part, it would be helpful."

I am interested in many parts, from the plastic gas tank to the steel tube frame used to hold the lights, instruments and fairing. I started to read the hal.archive and think it may be usefull but it will take time. College and Physics classes were some time ago. I find the "Materials selection chart" a fascinating thing (when was that created, if anyone knows?).

I was hoping for some rule of thumb info. but may not be so lucky.

As for a specific part, lets use the steel tube frame that holds the lights, instruments and fairing. I think this could be made of many things and CF tube or Al tube welded together are on the list. I think CF could be made in a smaller dia and thus lighter format but this is only guess work. The frame work is, at present, steel with joints connected with screws or bolts and this could be changed, at least in part. I know this could be a complicated engineering design if one wants to get into it. To make it out of Al would be relativly simple as I could do most of the work myself. CF is more difficult as it is something I would need to learn. But I have some crazy shortcut ideas (mostly from lack of ANY experience) like using CF fishing rod tubes or golf club shafts.
This is what it looks like:
If you plan to do the carbon fiber work yourself, then I would strongly suggest teaming up with someone who works with this material. When creating structural elements with carbon fiber, the joints, direction of weave, glues, layers, etc., will have a significant impact on what types of loads it can handle.

For example, a lot of car enthusiasts purchase carbon fiber hoods from Ebay. The problem? Regular hoods are designed to crush on impact (like a head-on collision). If a carbon fiber hood is not properly fabricated, the hood may very well cut through the windshield and driver in a collission.

So, let's say you would like to use a carbon fiber fishing pole and cut it up and glue up, the final product may not have the structural integrity that you are looking for. Also, when working with fibrous materials like carbon fiber and fiberglass, they are similar to asbestos and are cancer causing. Use seriously good respiration. Not the time for those Home Depot paper hospital masks.

The nice thing with aluminum is that you can weld it and bend it (for these purposes, I'm keeping everything very basic and not going to get into heat-treated aluminums like 7075T6, etc.). This should be your material of choice for most of your work. Reactive metals like titanium and magnesium sound really cool but can create fireworks if you are not careful.

After you have learned to work with aluminum, you may wish to consider working with Inconel (nickel steel) in super thin segments. Inconels has unique properties. Look into it.

Remember when it comes to motorcycles, frame dynamics is not as simple as "the more rigid, the better." But if you are looking to strenthen other parts, you can always replace bolt fasteners with welds. Test it and add more support.

I think that you should go ahead and give it a try. It will be a great learning experience and you will grow to appreciate the arts of technology that much more.
 

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While they both have the same mass, they do not necessarily have the same weight (heavy implies weight, not mass).

Generally, the gold would be slightly heavier as it's cg would be closer to the cg of the earth (or whatever reference you are using), unless the feathers were distributed in such a way to have a lower cg than the gold, which is highly unlikely.

This assumes of course that both are weighed in the same place.

Tom
LOL you're right, but in layman's terms mass and weight are the same thing :D

Alas, good thing this is a bike forum and not a physics forum :eek:



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a few random toughts

Ah yes....the notorious "rule of thumb". Try to understand this comment first.... Engineers are paid to calculate, model and predict the outcome of a particular change. In other words, to understand the end goal and work to satisfy this.

If you have a lot of time and money and luck and will be happy with whatever result you get ( and likely you will due to your total investment)...then by all means just spend and hack to your hearts delight. In the end, you will not know what you have done because it was built on some very dopey assumptions as to the behavior, and similiarity to, metal. They are two TOTALLY different things that you naively wish to equate on a density basis.

What very nearly all motorcycle riders expect of their CF parts is something that is "somewhat" lighter ( and I use that term advisedly) and to look sexy -hence the term "Italian chrome". ( Wheels, being a primary load structure are a different subject entirely as they are critical to safety and follow different rules and we have different expectations of them. I think everyone on this site understands that pretty well.)

One quick comment on fairings. There are several vendors on this site which make these out of CF and they are quite good, but little is expected of them structurally other than to maintain some rigidity and be strong in their attachement points and have a great surface finish to the prepreg as required. They are the closest thing to the one to one analogy to metal that you wish. That is because the factory parts are made from extremely low grade composite materials built to be "good enough" and cheap and look good. The demands of strength and stiffness are relatively unimportant because the original materials are so poor and heavy. Thus substituting any CF is going to be an improvement. ( Think of it as substituting aluminum for brass.) Your tubular structure is VERY different.

And be prepared to change your expectations on a regular basis as the project progresses. Otherwise, I would spend some time totally understanding those sites which were given before investing any time or money.

Sincere best wishes in your effort

Also this quote: "If you have a specific question about a specific part, it would be helpful."

I am interested in many parts, from the plastic gas tank to the steel tube frame used to hold the lights, instruments and fairing. I started to read the hal.archive and think it may be usefull but it will take time. College and Physics classes were some time ago. I find the "Materials selection chart" a fascinating thing (when was that created, if anyone knows?).

I was hoping for some rule of thumb info. but may not be so lucky.

As for a specific part, lets use the steel tube frame that holds the lights, instruments and fairing. I think this could be made of many things and CF tube or Al tube welded together are on the list. I think CF could be made in a smaller dia and thus lighter format but this is only guess work. The frame work is, at present, steel with joints connected with screws or bolts and this could be changed, at least in part. I know this could be a complicated engineering design if one wants to get into it. To make it out of Al would be relativly simple as I could do most of the work myself. CF is more difficult as it is something I would need to learn. But I have some crazy shortcut ideas (mostly from lack of ANY experience) like using CF fishing rod tubes or golf club shafts.
This is what it looks like:
 

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bevel: excellent random thoughts. as an aside i always thought is was nuts to use CF wheels for street application. just like for street a cf swingarm or any other critical component would be at best foolish. i remember when magnesium wheels were all the craze and how regular x-rays were required just to be sure..........i guess if you need a hobby this isn't a bad one assuming nothing critical is being built in the garage shop.....


rule of thumb: become an engineer or hire one :p
 

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Oh god...please don't start the notorious and incendiary CF vs. metal wheel thread again !!
( Do a search if you care to revisit that one.)

Yes, that is a GREAT rule of thumb !

That said, there is more bull shit and misinformation about CF as used on motorcycles than anything I can imagine* and for each of us it seems to mean something different. I think most bike owners really and truly like it for the beautiful weave pattern ( as seen through the clear resin) and it's association with highest performance racing machinery. Anything more than that, and it just gets weird. People are suckers on this stuff.

My favorite anecdote: some years ago Bimota sold a bike that had a CF shift linkage. The sex appeal was obvious... a real stunner. But after a few minutes of slobbering my riding buddy and co-worker started doubting the design. He analysed the design and found that it weighed TWICE what the comparable aluminum rod weighed. Bimota clearly understood that they needed to add a great deal more CF fiber to equal the strength of the dumb old aluminum part, and that some fool would gladly pay for the sex appeal.

Ah marketing....plant a naive idea in a buyer's head and gently lift his wallet.

bevel

* on second thought, exhaust systems rate a close second.

bevel: excellent random thoughts. as an aside i always thought is was nuts to use CF wheels for street application. just like for street a cf swingarm or any other critical component would be at best foolish. i remember when magnesium wheels were all the craze and how regular x-rays were required just to be sure..........i guess if you need a hobby this isn't a bad one assuming nothing critical is being built in the garage shop.....


rule of thumb: become an engineer or hire one :p
 

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Also this quote: "If you have a specific question about a specific part, it would be helpful."

I am interested in many parts, from the plastic gas tank to the steel tube frame used to hold the lights, instruments and fairing. I started to read the hal.archive and think it may be usefull but it will take time. College and Physics classes were some time ago. I find the "Materials selection chart" a fascinating thing (when was that created, if anyone knows?).

I was hoping for some rule of thumb info. but may not be so lucky.

As for a specific part, lets use the steel tube frame that holds the lights, instruments and fairing. I think this could be made of many things and CF tube or Al tube welded together are on the list. I think CF could be made in a smaller dia and thus lighter format but this is only guess work. The frame work is, at present, steel with joints connected with screws or bolts and this could be changed, at least in part. I know this could be a complicated engineering design if one wants to get into it. To make it out of Al would be relativly simple as I could do most of the work myself. CF is more difficult as it is something I would need to learn. But I have some crazy shortcut ideas (mostly from lack of ANY experience) like using CF fishing rod tubes or golf club shafts.
This is what it looks like:
Rule of thumb, no. But that methodology can be used to analyze many materials using a variety of criteria including strength stiffness as well as cost.
 
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