Project #4 from Spike : Custom Triumph Touring Bike Bobber Seat Set-Up

[Spike]

Hey folks, i've got a new project to start posting work on.

I've got a triumph job in the shop. Turning a sportbike into a long distance touring bike for a customer. I'm not really one for posting up pictures of my real work in progress, but this is one little snip-it of a 'project within a project' that i think won't hurt to leak out ahead of time, and doesn't show too much of the job in progress. I just started this part of the project yesterday, and i figure i'll have it wrapped up by mid-week. I've got some 6061 tubing, and plate in the construction, and it's all tig welded.

One of the parts of this bike is that it will have a suspended bobber seat, riding on coil-over mini-shocks. The interesting setup of the seat shocks to keep a low seat profile, and the abnormal shape of the swingarm made creating all the brackets and the shapes of the supports a little more interesting than normal, so i figured i'd share.


First things first, finding the centerline of the support bracket i welded in the top of the structure to mount the shocks off of. The bottom of the shocks are actually going to hang into the negative space in the swing-arm, so that the seat height won't have to be raised way off the bike.
At first thought, i was going to try to bend pieces to make some nifty and clean little mounting tabs and weld them in... but the bends to get down into the swingarm are awkward enough and sharp enough so that a regular bend won't do it, and trying to heat bend the aluminum into place just makes the material tear and fall apart (even with annealing it before-hand).


So i have to do it the hard way, cutting out individual mounts and grinding them smooth and matching and all that mess. So, templates were made and the arms cut out of some 5/16" 6061 plate on the bandsaw.


Bolted together with bits of scrap square tube mocked in as placeholders for the shocks, they kind of look like little T-Rex arms when they're put together... and i had some fun making dinosaur noises and waving the tiny arms around for a couple of minutes before i remembered that i'm supposed to be a bike builder, and thus, too cool for that sort of thing.

[Spike]

I cut off a piece of 1/4" flat stock aluminum and clamped it into place to add some rigidity and strength to the structure of the mount. Lock it all in place with clamps and vises and it's ready for welding.


Quick welds and some cool down, and the support is ready to get clamped onto the bike for weld-in.


A small army of clamps is important in a fab shop. Being able to reach out and grab any number of clamping device in order to hold your work is invaluable. It will save you time, money, and sanity.


After a partial burn in, the support is in and ready to finish mock up. Only the top welds are completed, These are just to hold everything tight. I'll finish the weld-up the next time i have the back part off of the bike, which isn't too far off, because it's going to come off and on many more times in this project.

another pic


After a little more burn in, i'm ready to get the front mounts going.


The front mount is easier, it's just a mount that holds the front hinge so the seat can pivot up and down on the shocks.
This gets welded to an existing support on the frame of the bike that is conveniently in the correct spot for the front mounts. The unused portion of the mount here will get chopped off at the mount. This was the old support for the stock gas-tank, which will not be used in my final project.


The nose mount and the shockmounts are ready, now it's time to get to the framework and seatpan... which will all also be aluminum on this project.
I'll be back at work on this monday, and get more pictures for you next week.

[Spike]

Alright, today i didn't get much done on the supports... i had to run around doing parts orders and making pieces for other projects in the shop... so here's what i got done on the structure...
I welded in the front mounts for the pivot on the front of the bobber seat on Friday, and today, i marked and chopped the rest of the old supports off of the bike because they are no longer needed, and are in the way.
I masked off the area with metal tape to keep shaving and sparks out of the works that is sitting on the top of the motor (electrical connections, sensors, fuel line, etc.). The metal HVAC tape is a useful thing to keep around the shop. It doesn't burn up like paper tape, doesn't melt like plastic tape, is stronger than other tapes, and takes a lot of abuse without failing.


To get the portable band-saw into the area to cut the supports off meant i had to take off the rear support section, which let me weld up all the unfinished welds that i could not get to with the assembly on the bike.

After this, i made the threaded insert, and the piece of aluminum that will be the front of the pivot on the seat's bracket. I cut the pivot out of 1" 6061 aluminum round, and drilled a hole through the center for the threaded insert to go through. After it was all together it looked like this.


After some measurement and mock-up i cut the seatpan blank out and got it ready to be made into a seatpan.


I fiddled around with some aluminum solid stock bending out the supports and holders for the seat, but there's not much to take a picture of just yet, so it'll wait for another day when it actually looks like something.

[charger891]

Nice work man, like the support!

[Spike]

Nice work man, like the support!

Thanks charger!

[Spike]

Seatpan time!

I ran the seatpan through my home-made radius brake, to get it's most basic shape (in the last post).
After that, the work gets slightly more involved. It gets some english wheel work...

... and then some more work, and it's ready to test for shape and fitment.

Once it's properly curved for absolute posterior comfort... then the easy part is over.
First step, since this is aluminum, any area that is going to have a lot of stretch and shrink to it will need to be annealed. So, out with the oxy-acetylene setup.
Adjust the flame to a sooty acetylene flame and apply the soot to the area that will be worked...

... then go back to a neutral flame and burn off the carbon, and you are annealed.

It is important to note, that you have to move QUICKLY when annealing sheetmetal. annealing happens at 800-900 degrees, and melting happens at 1100 degrees. Thin aluminum sheetmetal will go from annealed to molten puddle of slag very quickly. I think to remind everyone of this... because i blew a big hole towards the edge of the pan that i had to fix when i was annealing.
If you are looking for how i fixed this check out this thread i started for all of that mess.
2625-Project-6-from-Spike-Aluminum-Seat-Pan-Hole-blow-through-repair

Now, i'm afraid i have to be a little vague... but there's a lot of stretching, tucking, shrinking, rolling, more annealing, etc... and a couple of hours later i have a strong, finished, shiny seatpan.

Another angle


Now it's ready to make the pivots and brackets and supports.
Stay tuned for the rest.

[Spike]

next next next...
yes there's more.

Now, next step is bending up some brackets. This seat is going to be a touring bike, so this thing is going to get a backrest. So i fired up the oxy-acetylene and started heat bending some 1/2" aluminum bar.


getting two bars that match, and line up even on the pan is a little trickier, but after not too much trouble i've got two supports ready to go.



Welding on some mounts and positioning, i'm ready to make the backrest pan and mount it.

[Spike]

Next is the backrest... and it's much the same process as the front seat, lots of annealing and hammering, tucking and shrinking and wheeling and rolling... and then it comes out something like this.



adding the mounts to the back...



and then i used some 1/2" flat bar to make the bracket on the top of the support rails to hold the backrest. I broke out the torch again, and used a little scrolling jig i rigged up in the shop and bent the flatbar to match the contour of the backrest pan.


Finished and ready to turn into a seat!

[Mike J]

That is some nice work! How long you been doing this?

Cheers,

Mike

[Cippee]

Awesome work but what the heck kind of tire in on that bike? It looks like a car tire like a 195-50-14.

[charger891]

Nice job man!! looks really good! I`ve seen some radical seat skins on your site! what kind are you putting on this one?

[Spike]

That is some nice work! How long you been doing this?

Cheers,

Mike

Thanks Mike.
I've been in the car and motorcycle business for about 10 years, in the custom business for 8.

Awesome work but what the heck kind of tire in on that bike? It looks like a car tire like a 195-50-14.

Yepp... it's a car tire. The customer is a 'long haul' rider, and to take the extra weight and mileage that he puts on the bike he installed a car tire on his bike. He says it works fine. Since the tire isn't ridiculously wide or flat, it still turns okay.

charger891

Nice job man!! looks really good! I`ve seen some radical seat skins on your site! what kind are you putting on this one?

Thanks! I've put in lots and lots of hours on those seats to get to the level i'm at now with leather tooling.
I don't know what's going on this one yet. It's a long distance rider, so it won't be a flashy show piece, just indestructible and long lasting, wrapped around 2 layers of memory foam padding.