Girder front end expert required...

[JDD]

Anyone can help me with geometry for a girder front end. I always planned to have a set of girders but now I’m getting a few bits together I’m questioning wheel sizes etc I chose to go with the frame size and clearance sizes.
Main question is do I have enough clearance as the girder strokes up to run a 21” front ( see frame dimensions in pic.
Cheers anyone....

[Luky]

Anyone can help me with geometry for a girder front end. I always planned to have a set of girders but now I’m getting a few bits together I’m questioning wheel sizes etc I chose to go with the frame size and clearance sizes.
Main question is do I have enough clearance as the girder strokes up to run a 21” front ( see frame dimensions in pic.
Cheers anyone....
[ATTACH=CONFIG]86106[/ATTACH]

Make sure the tires are on the wheels before taking measurements!
Tire OD can vary as much as 1 inch.
Contact the makers of the forks FIRST to make sure the measurement of the frame to ground is
from the bottom of the bearing cups or bottom of frame.

[Dougtheinternetannoyance123]

I have some copies of the old Jammer chopper guide vols 1-2-3 etc etc.. and they posted some cool tech on proper brake mounting and setting up a wheel on springers and girders, but there is a page also for various types of fork lengths which is somewhat helpful, but still hard to tell until you try.
Im sure TNC will be along with some cut and paste and reams of info which would be helpful, but if he cant find an online version I can scan some pages of the Jammer chop guide.

I have several Girders and springers in the shop. Didnt get around to it last week and temps are currently in the high 90s and pushing 100 deg F so we shall see how that goes, but I was going to post a whole series of photos on chop frames and geometry in the tech section of this board. "Reference standard Chopper frames"...

I could snap some photos if you like with some of those front ends on a frame or two and post measurements. I have some sweet frames,, one is a Santee, a Paughco and some others.

In the interim, can NEVER go wrong with this guys excellent webpage with TONS of tech, One of the best resources on the web!
See: http://www.chopperhandbook.com/rake.htm

[TriNortchopz]

What is the horizontal distance between the centre of the front axle and the bottom of the frame neck (at 25.4"high)?
what is the amount of offset(horizontal measure) from the front axle to a centerline drawn through the neck (at 30*)?
Save me doing calcs using the old sine law(a/sineA=b/sineB=c/sineC) and a2+b2=c2

From your research, have you determined the amount of offset from the center of the neck to the center of the front girder linkage pivots? Were you considering a built in adjustable rake?

Just a good pic from the CBH:

(cause ya always need a picture)

Guessin' you already read these:

2012 Thread: Building a girder...suggestions please

http://www.chopcult.com/forum/showthread.php?t=24091

2011 Thread: Girder Plans

http://www.chopcult.com/forum/showthread.php?t=13374

(some great links in here)

2016 Thread: Girder forks

http://www.chopcult.com/forum/showthread.php?t=48274

2013 Thread: Picture Thread: Girder Front Ends

http://www.chopcult.com/forum/showthread.php?t=27119

ChopCult news blogspot: Voodoo Vintage fabrication girder front end

http://chopcultnews.blogspot.com/2016/02/voodoo-vintage-fabrication-girder-front.html

I haven't got to your original question for geometry yet...

[53Bash]

Easiest way to know for sure is draw up an accurate diagram or make a full scale mock up from wood / cardboard / foam. At a guess I'd say yes assuming your wheel position is accurate, the girder has about 4" trail etc... but its really just a guess given all the unknowns.