BO15 Scrapyard Mule

[tjwilson]

I can squeak in maybe seven days so lets give it a try. Ready, set, go...

This isn't the bike I'm planning but it is the plan that led up to the planned bike. I'd been doing a few thumbnail sketches and started liking the idea of taking a classic design and doing an extreme stretch and lower. These sketches are early ideas using a Spaceliner as inspiration. Scrapyard Mule is a test mule to prove out the geometry and determine if the ride is at least tolerable. The ergonomics will also, hopefully, help determine if the idea is worth pursuing further and to what degree.

This was the process of coming up with dimensions.

Thumbnails

Tracing Thumbnail in Illustrator Using Known Tire Diameters, Crank/Seat/Bar Spacing, Trail

Printout of First Pass Dimensions

Additional Sketching Over Printout of Thumbnail Trace Dimensions

Final Mule Dimensions

 

[tjwilson]

Day 1

Gathering parts and putting them in place.

 

[Brian macumber]

I like but 7 days?

 

[tjwilson]

I like but 7 days?

7 days - ish? Trying to fit this in between other home repair projects. Won't be painted for sure, not going to sweat details so much. Want something I can get some pedal time on to test the layout. It usually takes me a really long time to finish a build.

 

[hamqqea]

Final Mule Dimensions
View attachment 129783

Hello,
Did you start designing the frond end around a specific trail value? How do you anticipate the steering will behave with a 50+ degree rake? Which component is most crucial in your opinion, keeping within reason, for 'ideal' or desirable steering? From your trail it would seem to be a pretty nimble ride, unlike a chopper with a 6'' trail and a 45 degree rake which feels heavy and flops.

Can you explain at all the relationship between high rake and a sub 3'' trail?

I read you wanna move fast and it's a test... I'm curious

 

[nosferatu1381]

I can squeak in maybe seven days so lets give it a try. Ready, set, go...

This isn't the bike I'm planning but it is the plan that led up to the planned bike. I'd been doing a few thumbnail sketches and started liking the idea of taking a classic design and doing an extreme stretch and lower. These sketches are early ideas using a Spaceliner as inspiration. Scrapyard Mule is a test mule to prove out the geometry and determine if the ride is at least tolerable. The ergonomics will also, hopefully, help determine if the idea is worth pursuing further and to what degree.

This was the process of coming up with dimensions.

Thumbnails
View attachment 129779

Tracing Thumbnail in Illustrator Using Known Tire Diameters, Crank/Seat/Bar Spacing, Trail
View attachment 129780

Printout of First Pass Dimensions
View attachment 129781

Additional Sketching Over Printout of Thumbnail Trace Dimensions
View attachment 129782

Final Mule Dimensions
View attachment 129783

I love it

 

[tjwilson]

Hello,
Did you start designing the frond end around a specific trail value? How do you anticipate the steering will behave with a 50+ degree rake? Which component is most crucial in your opinion, keeping within reason, for 'ideal' or desirable steering? From your trail it would seem to be a pretty nimble ride, unlike a chopper with a 6'' trail and a 45 degree rake which feels heavy and flops.

Can you explain at all the relationship between high rake and a sub 3'' trail?

I read you wanna move fast and it's a test... I'm curious

Awesome questions. To be honest I'm totally shooting in the dark on this one. I really don't know what kind of handling it will have. I'm hoping for something that is nimble without flop. Although nimble is relative I suppose. With that long of a wheelbase it will never be nimble. The amount of rake is purely for aesthetics. The trail came about as a distance that has worked in the past... for builds with less rake. Completely an assumption on my part that it will work here. As for what's most crucial, I'm guessing the amount of trail is going to be key to making this thing ridable. The heart of the plan is to not get too invested in time or details so I can cut, re-weld, change and piece together something that is ridable but still has some of the feel of the proportions in the early sketches. Or, if nothing else prove that I need to go back to the drawing board.

 

[tjwilson]

Day 2

 

[OddJob]

TJ's back at it again! Have fun with this. Rarely does one see so many different measuring devices in a single build thread photo! Math matters!

 

[kingfish254]

 

[hamqqea]

I'm hoping for something that is nimble without flop. Although nimble is relative I suppose. With that long of a wheelbase it will never be nimble.

I meant to suggest low steering input in a straight line. What I can't envision is how your steering axis factors in.
I notice a twitchy low trail can cause shoulder fatigue. A high rake and trail messes with me more psychologically. The combo of pedaling and steering can make the bike feel overly heavy. I don't mind less than perfect steering control with exaggerated geometry. It's the physical and mental fatigue that gets in the way of the fun sometimes.

Thanks for the reply... Hope the result is a pleasant surprise.

The concept bike is very cool and interesting

 

[tjwilson]

TJ's back at it again! Have fun with this. Rarely does one see so many different measuring devices in a single build thread photo! Math matters!

View attachment 129898View attachment 129899

Is it measure once and cut twice or cut twice and measure once? I can never remember

 

[tjwilson]

I meant to suggest low steering input in a straight line. What I can't envision is how your steering axis factors in.
I notice a twitchy low trail can cause shoulder fatigue. A high rake and trail messes with me more psychologically. The combo of pedaling and steering can make the bike feel overly heavy. I don't mind less than perfect steering control with exaggerated geometry. It's the physical and mental fatigue that gets in the way of the fun sometimes.

Thanks for the reply... Hope the result is a pleasant surprise.

The concept bike is very cool and interesting

Yeah, battling for control is never fun! I've got my fingers crossed.

 

[tjwilson]

Day 3

 

[tjwilson]

Day 4

 

[tjwilson]

Day 5

 

[Psychographic]

That is one sexy BB mount!

 

[MattiThundrrr]

I love the step by step build-a-chop format of this thread.

 

[tjwilson]

That is one sexy BB mount!

Seeing the design and fabrication magic you've been working I consider that high praise. Thank you.

 

[tjwilson]

I love the step by step build-a-chop format of this thread.

Thanks. I think it's an artifact of OCD and the fear that I'm going to forget how I did something.