SPACELINER PITMASTER SPECIAL

[tjwilson]

SPACELINER PITMASTER SPECIAL
Spaceliner, smoked low and slow with a touch of hot rod rub.

THE RECIPE
A mix of mid-sixties Spaceliner styling cues, a long wheel base (64"), low seat position (24"), shallow head tube angle (50.5°), big/little wheel combination, ten speed indexed trigger shifter, disc brake, and high rise handle bars. Mmmm, I can already smell the hickory.

MAIN INGREDIENTS
While there will be plenty of "seasoning to taste" along the way, here's what I'm starting off with...

 

[tjwilson]

HUBS, TIRES & RIMS
Hot rod rub(ber) big and littles.

Out back is a Vee Tire 26x4.0 Zig-Zag mounted to a Classic Cycle (36) hole 82mm wide polished aluminum rim. Polished but, rim will need more sanding and buffing. After all purty and shiny it will be laced 3-cross with 13g black spokes to an Origin8 FB-2000 170mm rear hub. This tire/rim combo is pretty tall at just under 29" diameter.

Up front is a 700x32c Continental Ultra Sport mounted to an Origin8 (32) hole deep-V TA42 rim in silver aluminum. This rim's gonn'a need some sand and buff too. After the polish treatment it will be radially laced using 13g black spokes to a 100mm Origin8 SS-1101 hub.

 

[tjwilson]

BOTTOM BRACKET & SPINDLE
Here's an image of the hubs with the bottom bracket assembly. Bottom bracket is a 100mm wide shell, spindle is 164mm wide to help get around that 4" rear tire.

 

[tjwilson]

CRANK & CASSETTE
Crank and 42T front sprocket are from a Shimano Arabesque 600 set that I picked up at a swap meet a couple years ago. The rear cassette is a Shimano CS-M771 XT 10sp, 11-32T (11-12-14-16-18-20-22-25-28-32). I chose the rear cassette tooth range based on the gearing of a previous build (Shortbow) that used similar shifting components. The Shortbow gearing has proven to be pretty much spot on for my riding "style". Only problem is that build had a 20" wheel/tire combination. This new build has 26" so a little math was required.

Some internet searching found info on gear inches. Basically a way to compare gearing using distance traveled per one turn of the pedal. This is the formula:
Tire Diameter x Front Tooth Count / Cassette Cog Tooth Count = Gear Inches

A general rule of thumb is:
Up to 30 gear inches is relatively slow/easy gearing
30 to 70 gear inches is good mid-range gearing
Over 70 gear inches is faster/harder gearing

Here's the numbers for Shortbow which has a large diameter Apache Fatty 20x4.0 tire with a 23.27 inch diameter.
Low Gear
23.27" x 42t / 25t = 39 gear inches
Center Cog on Cassette
23.27" x 42t / 15t = 65.156 gear inches
High Gear
23.27" x 42t / 11t = 88.849 gear inches

The numbers for the Pitmaster Special with a 26x4.0 Zig-Zag tire with a 29" inch diameter.
Low Gear
29" x 42t / 32t = 37.7 gear inches
Second Largest Cog
29" x 42t / 28t = 43 gear inches
Center Cog on Cassette
29" x 42t / 18t = 65.9633 gear inches
High Gear
29" x 42t / 11t = 109.7345 gear inches

Pitmaster Special comes pretty close, actually it will have a bit more range. Honestly I was most concerned about the low range gearing... remember low and slow. This cassette also has a cog range that allows me to use a short cage derailleur again. That combo worked really well on Shortbow.

Here's a picture that hopefully makes up for the math detour.

 

[tjwilson]

INDEX THUMB SHIFTER AND DERAILLEUR
SRAM GX shifter and the short cage derailleur mentioned. Defaulting again to the Shortbow build. Hoping that I might be able to fit the shifter into a tank and create custom paddle type shifters mounted to the bars. But, I'm getting way ahead of myself. That will be a long way off yet.

 

[tjwilson]

BRAKES
I wanted to contrast the lace patterns between the front and rear wheels. A 3-cross in back, radial up front. My understanding is that a radial lace pattern doesn't offer much torque strength. Because of that concern I decided on a large 203mm disc and twin Avid BB7 calipers mounted to the rear wheel and no brakes in front. I'm using mechanical calipers for a couple reasons. Hydraulics work great but the levers seem a little too bulky for what I have envisioned for this build. And again, this will be another potential opportunity for custom levers.

 

[tjwilson]

FENDER
The design really needs fenders. The best and most cost effective option I could find were inexpensive motorcycle fenders. Sections of two fenders will be required to get the wrap that I want. These are heavy and need considerable smoothing. A lot of material will be removed and I've got my fingers crossed that the diameter works out.

 

[tjwilson]

FRAME
To start I have some straight tubing in addition to the 100mm bottom bracket and a length of raw head tube stock. Now the fun begins!

 

[MattiThundrrr]

Awesome stuff. Thanks for the gear inches lesson. I'll be ruminating on that for a while

 

[hamqqea]

Linked the current gears following your build.
http://www.ritzelrechner.de/?GR=DER...,32&UF=2260&TF=90&SL=2.6&UN=KMH&DV=gearInches

The bike you're building will feel considerably different from the Shortbow. I'd save the gear factoring for later. You have plenty of gears to work with. You're likely to use gears 2-6. You may need to go lower than 37'' for climbing hills, especially with a rear tire @ 30 PSI and the geometry listed. You'll feel the weight on level ground at 60 gear inches from what I'm seeing.

Why 13 guage spokes though? 12g will give the rear wheel a more robust appearance. I've been lacing 10 gauge lately. If it wasn't for cost and weight I'd use 12 and 10g more often.
I wouldn't be concerned with spoke patterns regarding brakes. 32h radial is plenty.


Good stuff

 

[Wildcat]

I use this for all the gear calculations: It will show you your speed at cadence and a bunch of other stuff.
https://www.bikecalc.com/speed_at_cadence

 

[Verrt]

Love the recipe. Can't wait to see it out of the oven... or deep fryer

...maybe a crock-pot.

Metaphors.

 

[tjwilson]

Linked the current gears following your build.
http://www.ritzelrechner.de/?GR=DER...,32&UF=2260&TF=90&SL=2.6&UN=KMH&DV=gearInchesView attachment 150804

The bike you're building will feel considerably different from the Shortbow. I'd save the gear factoring for later. You have plenty of gears to work with. You're likely to use gears 2-6. You may need to go lower than 37'' for climbing hills, especially with a rear tire @ 30 PSI and the geometry listed. You'll feel the weight on level ground at 60 gear inches from what I'm seeing.

Why 13 guage spokes though? 12g will give the rear wheel a more robust appearance. I've been lacing 10 gauge lately. If it wasn't for cost and weight I'd use 12 and 10g more often.
I wouldn't be concerned with spoke patterns regarding brakes. 32h radial is plenty.


Good stuff

Awesome resource, thanks. I've found that as I start new builds I'm checking back in on previous builds more and more. I'll definitely get use in the future out of the links you and @Wildcat have posted.

This is going to have some heft to it. Luckily the "hills" in Southeast Michigan are pretty much just speed bumps elsewhere. A cruiser for nice flat terrain.

Spoke size... the geometry for this is coming from the Scrapyard Mule 2.0. It felt like there was a lot of side force on the front wheel while turning on that. Had a gut feel I needed to go with more stout spokes than 14g. I settled on 13g because I was afraid I might need to drill out the holes in the hubs if I went thicker and didn't want to mess with that. And... now keep in mind this is through a thick lensed post-purchase filter... to my eyes a Spaceliner almost looks spindly. In trying to capture some of that design "feel" it might help if the wheels have a little visual lightness to them rather than what I've typically seen on stretch cruisers with thicker 12g or 10g spokes. I think that's why thicker spokes didn't occur to me, you know, looking back through a thick lensed post-purchase filter.

You mention a 32h radial pattern would be just fine for braking. I bet I got the impression it might be an issue reading of an application somewhere along the way that had a lower spoke count. If I run into trouble working out the twin calipers in back or end up not liking the look it sounds like I can move a disc up front without trouble. Thanks.

 

[tjwilson]

I use this for all the gear calculations: It will show you your speed at cadence and a bunch of other stuff.
https://www.bikecalc.com/speed_at_cadence

Awesome, thanks.

 

[tjwilson]

Love the recipe. Can't wait to see it out of the oven... or deep fryer

...maybe a crock-pot.

Metaphors.

Smoker... already been chopping wood

 

[tjwilson]

BENDING SOME METAL
I've done this a few times in the past and have had good luck with it. I drew a profile line drawing of the design in Illustrator and then printed it out full size. I shift the drawing while printing so that I end up with an 8-1/2" x 11" mosaic that I tape together.

The full size profile is used as reference for bending and assembling the tubing. I started with the pieces that will make up the main backbone of the frame.

With the pieces tacked together I clamped the entire assembly and finished up the welds.

 

[tjwilson]

BENDING THE TWIN TOP AND MID TUBES
To get matching bends I first welded the tubes up in pairs. The tubes were then filled with sand and caped before going through the tubing roller. I also bent sections that will be sleeved on to the end of these tubes to get them around the rear wheel and fender to the rear drop outs.

 

[tjwilson]

TOOL SPLURGE
A little detour from build pics... I've been eyeing this fixture (from chopsource.com) for a while and couldn't resist it's pull any longer. Complete overkill for the volume of building that I do but I couldn't be more excited. It's absolutely beautiful and I may actually be able to finally put together a totally straight frame now!

 

[tjwilson]

WHEEL AND FENDER TEMPLATE
I'm having a little trouble visualizing exactly how to run the top, mid, and chain stay tubes around the rear fender, wheel, and brake disc. I printed out full size cross sections and mounted them to cardboard to use as reference. I'm hoping this will help me keep the frame tight to the rear wheel.

In fixture, side view, very early mock up.

 

[MattiThundrrr]

That frame jig is siiiiiiiiiiiiiick!