sharpear

Hey guys,

Thanks for the help on the previous questions. "Sheldon Brown's" website is pretty damn informative!!! But i still cannot seem to find CAD drawings of the rear hub? Would anyone know where i could get such drawings?

Thanks again

biker7

you likely won't find any CAD drawings of any rear hubs in CATIA, UG or any software as they are always proprietary. Over and above...you would need compatible software to read them. I have Catia V5 at work and on my home system and it is very expensive. Why would you want the CAD drawings?
George

powers2b

Sharpear,
Did you even read my post on your last thread?
https://www.bikeforums.net/bicycle-mechanics/104432-what-dangley-thing-hub.html

Enjoy

biker7

got it powers2B. Sharpear...not to cast a cloud over what you are attempting to do but I develop CAD drawings for a living and you have a real steep uphill climb. Yes, everybody starts someplace but you are tackling a very complex mechanism with little background. Creating CAD drawings is much more that measuring component/assembly geometry and either creating a wire frame with surface or 3-D solid modeling...its all about creating the GD&T by establishing datums which is the cornerstone for how any assembly will fit together and function properly if mass produced. I wish you well in your pursuit and don't know your technical background but it is not only hard to recreate something but much more difficult to improve upon a mechanism like an internally geared hub without a thorough working knowledge of not only manufacturing tolerances of the individual components...what is ground versus machined for example..but internal tolerances necessary to sustain proper clearances for adequate function. Most gearsets are computer generated...I have created them on CAD and not for the uninitiated.
Good Luck,
George

genec

How about in a more universal format... such as IGES. or perhaps DXF... although not so universal, it is commonly used.

Many CAD programs can exchange data in these formats. There are even free viewers for for DXF formated data.

Just some ideas.

supcom

You're not going to get any CAD files of a hub. Forget about it. If you want some, you need to draw them yourself. Nobody gives their designs away.

Unless you have been assigned to redesign an internally geared rear hub, use a typical freeqheel or freehub hub for your project. Go down to a local bike shop and buy the cheapest hub they have. Tell the owner what you'r up to and maybe you'll get a good deal. If you can't get something for less than $30, then go to a thrift store and buy an entire used cheap bike. you may get one for $5 or so.

Take the hub apart and you'll see how it works. Make some measurements of it and you can draw it up yourself close enough for a class project. Then apply your mechanical expertise and do your redesign, analysis, and make the modification drawings as required.

biker7

Sharpear...to elaborate on supcom's good advice above, you do need to choose the hub you target for your project/redesign carefully. My personal opinion is you would be well over your head chosing a geared hub due to its overwhelming complexity. However if you choose too simple of a hub, you will deny yourself much opportunity for optimization as the design will already be simple. BTW simple in engineering terms is preferred and what every designer ultimately strives for as many times simple designs are the highest evolved. It is hard to design a simple machine. I have attached a couple of late model Campy rear hubs to illustrate how Campy differentiates their product for their rear hubs. Note the hub with all the complexity turns out to be much lighter than the simple rear hub I have by comparison for my Campy Vento wheels. Hub weight isn't neccessarily a function of complexity as underscored by this example.
I believe the high end Campy rear hub shown is a good opportunity for improvement. Improvement in engineering terms is often related to reducing content or integrating multiple components into one as a result reducing cost for the same durability and performance envelope. Have a look at two hubs which accomplish essentially the same thing and are a whole different magnitude in cost, weight and complexity.
Some further perspective,
George

sharpear

Hey guys,

Thanks for all your great help...and being very informative. The thing is, my project doesnt revolve around the CAD drawing...i just need one to show possible changes that i could make to a design to improve manufacturing time, possibly arrangment (i.e. not having to rotate the subassembly parts to fit other parts - time waste), making similar parts the same (ive noticed that some of the hubs - typically shimano types, have multiple hubs with a few seperate arrangements where several washers and spacers have been use of different sizing....i would aim to try and make them of the same origin such that costs would be minimized in batch production. Also if one washer is bigger and i choose the smaller one...the machining time to produce the hub would be less. Another area possibly might be the thread of the hub axle....minimising that will have a direct affect on the machining time and thus cost of production.

So as you see the project doesnt aim to redesign a hub in reference to tolerances, point stress analysis and other force/material analysis to reproduce a much more efficient hub...but rather understand how to redesign the hub where at a manufacturing level it could be altered significantly to large scale production in the areas of costing, machining time, reduction in component parts, reduction in degrees of complexity - i.e. reduce number of complex components as these will require large machining times etc....

Thus i have no real desire to waste my time drawing up a whole CAD drawing when dimensioning and tolerancing arnt of the projects importance. Ive just realised on the shimano site that the exploded views for their hubs will be satisfactory. Ive noticed that some designs have already incorporated my design characteristics mentioned and thus i shall most probably be able to just show these designs and how the changes that have been "made" will advantageously affect the final manufacturing volumes.

Thanks a heap guys, you have been a great help!

Aaron

biker7

I don't know what level class you are taking but without any deference to part tolerances, stress analysis, free body diagram of forces, any simplication to a proven design you make will be without foundation. The designs that you are studying have been scrutinized by teams of engineers...I am a product development engineer and understand the rigor involved. Not to say you can't improve upon designs out there...but not without intensive analysis. If your professor buys your proposal without an underlying basis for simplifying any design...say reduction in assembly complexity for reduced manufacturing cost...without a foundation for why you can eliminate parts and not adversely affect function...then you will succeed. Most are smarter than that. Your only hope is your professor never worked out in industry and designed something for a living...lol.
Good Luck,
George

sharpear

George,

The class i am taking is stupid...its an elective which i should have never taken. I am completing my degree in Mechatronic Engineering this year and i just need to waste credits around my final year project. I totally agree with you considerations of "part tolerances, stress analysis, free body diagram of forces" and i am not aiming to make anything of the design once finished.

It is a unit to understand the manufacturing principles that are available to todays working environment and i have to simply explore the alternatives. I also have to run a simulation of the design in a program called "Extend" - ever heard of it? So as i was saying before the lecturer/Course Administrator doesnt care about the CAD file so much, but rather the generalised idea of what possibly could be done. I have no clue whether these alterations are possible as i do not have the time nor money to piss-fart around and do such tests and hence why it is not the focus of the unit.

I have example files from a student of the previous year if you are interested. Just send me your email.

Enjoy

Aaron

biker7

Hi Aaron,
Never heard of "Extend"...hundreds of programs out there. Understand what you wrote. Best of Luck and since you are in the home stretch of getting your BSME, congratulations on your accomplishment...no small feat.
George