Tube Holding Success

The goal for today was to complete the tube holder and bore the seat tube up to size so the seat post would fit.  From the supplier the seat tube was slightly undersized so that the bike builder could ream up the tube to fit a standard seat post.  After a quick Google search revealed that most seat reamers cost in the neighborhood of 200 bucks it was obvious that an alternative solution was necessary.  Previously I welded a broken center drill to  the end of a steel rod in an attempt to fashion a boring bar.  Today the steel was shaped on the grinder and considering I have no idea how to grind lathe tools I am a bit surprised it worked as well as it did.  The finish was not quite the 32 finish I would have liked but the steel rod cost around a dollar so less than ideal finish on a part that will never be seen and a savings of 199 bucks seems like a good trade.  And I got to make a bunch of sparks!
    

        With the seat fitting nicely in the seat tube it was time to refocus on the tube holder for the lathe.  I left off previously with the lower portion of the fixture containing the threaded holes and the T slot features.  After cutting another section of aluminum bar to a similar size as the lower portion I drilled a couple thru bolt holes to hold the two blocks together as well as some threaded but counter bored holes between the two bolt pattern.  The counter bored holes allow a couple socket head cap screws to function as jacks jamming the T slot in place and preventing any movement.  The next step was to make a big hole in the center of the two blocks.  In order to determine where to drill the hole the fixture was bolted together and installed on the lathe as it would be used then using the live center as a scribe I marked the height where the hole should be drilled. (not a generally practiced machining process)  A second scribe line marking the center of the part resulted in a  nice target to aim for when setting up everything in the four jaw chuck.  After some tedious adjustment the part was in the right place and the long and boring process of making a 1.75" hole could be completed.  Even though this was quite a slow process I did end up making a huge pile of chips and some horrific noises as the tool chattered through the material. (my cuts may have been a little aggressive) The only thing left to do was make a slot in the collets so they could be compressed around the tubes which was easier said than done.  I have never been very good at math, hence my avoidance by becoming an engineer, but when you measure an end mill and it reads .5000 on your digital calipers and the shank on the key cutter you want to use reads .4990 you might assume if you can get the end mill in the tool holder you would surely be able to get the key cutter in as well right?  WRONG!  I tried for a few minuets to find a bur or something on the shank of the key cutter but it would not go into the tool holder or rather I could have gotten it into the tool holder but then there for ever more it would stay and not even Arthur would be able to remove it.  So back to the grinder where I precisely ground on the shank until I could get it into the tool holder.  Words of wisdom when using a key cutter on aluminum.  The aluminum alloy 6061 melts at over 1000 F which may seem like a lot but it is easily attainable with dull tools and excessive tool pressure which will result in much frustration while you try to pick/chip aluminum out of the cutter teeth. Once the collets were slotted a small amount of shim stock was used to get just the right compression on the tube and as you can see in the picture the tube holder turned out very nicely.  Now if only I did not weld all the aluminum tube into a big mess I could have tried the holder out, next time.

Machining and Millling the Seat Tube

Small elaboration on the previous post, while staring at some randomly selected chunks of aluminum contemplating how to hold a thin walled tube at just the right angle and index it such that the notches were lined up correctly it occurred to me that I needed another Corona. My previous drink that I had so carefully placed on the tail stock of the lathe had fallen and shattered into a wonderful wet mess of razer sharp aluminum chips and razer sharp glass bits. Anyhow, after I solved that problem it donned on me that if I made a common OD collet with a fairly precise machined ID that matched the tubes I will be cutting I could make a single tool that would mount in place of the tool post on the lathe. This would allow me to use the angle marks on the cross feed table and hopefully make repeatable cuts.


The only problem is the very limited supply of tools. Having no way to bore a hole in a block of aluminum 2.5" in diameter on the mill I decided the best course of action would be to use the four jaw chuck on the lathe and try to dial in the part and use the boring bar to make a precise hole. I planned on machining a T slot in the base of one large block of aluminum such that it would fit in place of the tool post and then bolt a second piece of aluminum on top. Once fastened together I would try my hand at setting up the four jaw and making the hole. Sounds easy right...

Some pictures of milled aluminum tubes

On a slightly different note, I have been doing a fair amount of welding of thin walled aluminum tube which I believe to be some of the hardest welding with which I have had reasonable success. (zinc + TIG + no idea what I am doing = fire hazard and poisonous yellow gas) So when I finished Star Trek I was pleasantly reminded how nice mild steel welds especially to tool steel, in this case an old center drill. However, earlier in the day I was messing around welding copper for the first time and I am confident that welding copper, even with a piece of wire for filler, is fantastic. It is so easy! Unfortunately, copper is also a fantastic conductor of heat which became abundantly clear while holding the filler rod in my left hand, even with the glove on it gets hot in a hurry. What it doesn't do in a hurry is cool off. Wait a long time before picking up the welded copper part then wait a bit longer. Once it is cool you can amuse yourself by heating up the oxide covered metal with your finger or breath and watching it dance around and the gracefully fly off into the air. Who would want to weld copper for fun?

Bike Progress

This week I am visiting my family in Pennsylvania for Thanksgiving and Ian is in Seattle making great progress on the bike. Here is email update from today.

From: Ian _______@gmail.com
To: Kaydee _____@yahoo.com
Sent: Fri, November 27, 2009 6:51:44 PM
Subject: Hey there

Hi Kaydee,

Hope your work project is going well.

I had a rather productive day working is Sparky's garage. I machined the head tube for your bike as well as made all the collets/inserts and half the tube holding fixture for the lathe.

After I watch star trek I am going to try to weld a piece of high speed steel to a rod in an attempt to make a boring bar so I can make your seat tube fit the seat. Now all I have to do is figure everything else out, if nothing else it will give me something to think about other than you while you are gone.

I just figured I would give you a little update on the bike. I miss you and look forward to seeing you next week.

Ian

Practice Welds

After I brought up the idea that Ian could weld me a bike, he immediately start practicing welding Aluminium.

He has made numerous crazy sculptures like the one pictured above. These metal pieces are filling up his house, his car, my house.

I am now an expert (or at least aware) at identify a "good weld" vs a "bad weld"

A website for fellow bike welders

It is amazing what you can find with a google search. Here is the link for the website where the bike tube were ordered from

Nova Cycles

Bike Lingo

Aside from the common bike terms like handbars, breaks, seat, and tires I learned some new key terminology for building a bike. A picture is worth a thousands words.

A few other words include:

Jig – A device that holds the pieces is the proper position while welding.

Chain break – a single link in the chain that hinged and the pin can be removed to allow the chain to be removed from the bike. However, Ian and I spent an entire day looking for the chain break on the Schamo chain only to find out that there was not one.

Modeling a bike in Catia

One of the first tasks for designing the bike was to understand the bike geometry.

For work Ian designs machine parts in Catia, so it was a natural transition for him to use this high dollar software to determine all the proper alignments for a bike.

Silly me thought that all bikes use the same geometry but apparently not. The angle of my top tube and seat tube will be 72 degrees.

Part of this modeling included Ian having to replace graphic card on his work computer. Apparently the Dell M90’s have a cooling issues when not properly vented. This translates to do not place laptop on lap while working.

The pictures below show my new bike.

I am getting excited!