Lurker's V-twin build

GoldenMotor.com
Lurker

Lurker

New Member
Jan 29, 2010
403
133
0
Pittsburgh
I don't know if I should post this or not, but here is some of the concept art I have done for the bike. The red dot in the photo indicates the driven unit of the cvt. Obviously the unit goes on the other side of the bike, but I am using this to illustrate my point. As you can see most of the ugly part of the keystone is hidden behind it. Hopefully this will help you guys understand how it will work.

Please don't be disappointed if the actual bike falls short of this rendering.

THIS IS ONLY A RENDERING.
 

Attachments

  • Like
Reactions: Tom from Rubicon
motorhedfred

motorhedfred

Member
Jul 31, 2009
421
17
18
United States
Man this is an awesome piece of work, so well proportioned and vintage looking. It's inspiring.

There's only one thing that's troubling me. You've planned everything so well I have to believe you've covered this, but the geometry of the steering seems to have no trail whatsoever. I truly hope I'm wrong about this, but if I'm not, it will be an evil handling bike.

Looking at the angle of the headtube and drawing an imaginary line through the center of it, the line should reach the floor several inches ahead of center of the front tire's contact patch. From the pictures it would appear that it's well behind that point.

Maybe something about a springer front end changes all that and I'm just ignorant of the fact.

Please check this out before riding it.....we'd like to keep you around for a good long time.

My apologies if I'm wrong or out of line.

MHF
 
Mr.B.

Mr.B.

Well-Known Member
Oct 21, 2008
1,329
559
113
Upper Mississippi River valley
Hate to dog pile you as I’m have nothing but respect of your artistic approach and originality.

However mhfred has a point, with the triple tree & those long forward links you do have positive trail. That’s a lot of motor to have to deal with squirrelly steering issues.

Perhaps you could roll it around outside a little (downhill, etc...) to see just how hard it is to handle?

Easiest fix may be to pitch the head tube rake forward. With a heavy & powerful machine like that I reckon you would want around 1-1/2 to 2 inches of trail.

-Kirk
 

Attachments

Last edited:
  • Like
Reactions: Tom from Rubicon
Lurker

Lurker

New Member
Jan 29, 2010
403
133
0
Pittsburgh
Thanks for all the positive comments and concern for my safety.
To start this off I think it would be important for you all to know what inspired the front end. In order of importance
1923 hd: geometry
1919 excelsior: gusset, trail and rake
1911 hd: fork design
1911 indian: head tube length

Geometry is the key element to make any bike look and perform properly. My friends call me the bicycle snob, and make fun of me for talking about the geometry of a bike whenever I see one I like.

I have already done a push test with the v-twin and I can tell you the handling is not twitchy at all. It has a nice smoothness to it but it is also responsive.

Below you will find two photo the first one is my racing bicycle the other is a 1923 hd. The bicycle is unbelievably twitchy I am just using these photos so you guys can see I have done my research.

Also triple trees and linkages change the rake of a bike. the bicycle in the photo has a rake of 25mm most normal bicycle have 45mm of rake. The v-twin has almost 4 inches of rake due to the triple tree fork and linkage. This allowed me to keep the head tube steep and still have a adequate amount of trail.

Please look at the hd photo and then refer to the one Mr.B did of my bike. I think I am well with in the limits.
 

Attachments

  • Like
Reactions: Tom from Rubicon
motorhedfred

motorhedfred

Member
Jul 31, 2009
421
17
18
United States
Great ! I'm really relieved that you covered this. I felt bad about even suggesting there might be a problem. Thanks for taking my comments in the spirit they given.

MHF
 
C

curtisfox

Well-Known Member
Dec 29, 2008
6,081
4,056
113
minesota
Thats AWESOME! Not only satisfied them but informed others. Including me sometime when we go along and do things we kind of forget the responsabilty to do the math,or geometry. THANK YOU.
Is there some kind of book or post that tells all of this?................Curt
 
  • Like
Reactions: Tom from Rubicon
Lurker

Lurker

New Member
Jan 29, 2010
403
133
0
Pittsburgh
Curt, there is lots of stuff out there on rake, trail, and general geometry. Just do a search, Wikipedia has a really nice article on it. A good basic rule of thumb is if the axle is closer to the frame and head tube it will be twitchy. If it is further from the bike it will be sloppier. You need to find a happy medium that works for you. Measuring different bike is a good place to start if you are going to build a bike from scratch.

link to rake and trail
Bicycle and motorcycle geometry - Wikipedia, the free encyclopedia

If any of you are really in to old motorcycle or considering building a replica/tribute like myself I recommend you purchase this book. Lots of wonderful info about every little detail. I don't think this build would have turned out as well without it.

must have book for builders
Amazon.com: Early Motorcycles: Construction, Operation and Repair (Dover Books on Transportation) (9780486436715): Victor W. Page: Books
 
  • Like
Reactions: Tom from Rubicon
Lurker

Lurker

New Member
Jan 29, 2010
403
133
0
Pittsburgh
I got my sediment bowl the other day, but just now had a chance to install it. I was able to find one that was fairly small with a 3/8npt thread pitch just like older Harleys, just incase I should ever decide to use a normal petcock. I used a regular Harley petcock on my last bike and I was never really satisfied with the look of it, it was too modern looking.

The sediment bowl also helps fill the visual gap between the engine and seat tube. eventually I will add a toll box in that area, but this is a good start.
 

Attachments

  • Like
Reactions: Tom from Rubicon
You must log in or register to reply here.
Top Bottom