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View Full Version : Head Tube Angle Questions...



SirJoey
06-24-2008, 07:15 PM
Just wondering, why the 58 degree head tube angle, as opposed to 72 on a regular bike?

Also, how much leeway is there on this angle, one way or the other?

http://img384.imageshack.us/img384/7131/sirjoeysigmedij1.gif

TheKid
06-24-2008, 08:41 PM
It depends on how you want to set it up. Whatever angle you choose, you have to make sure you modify the fork to give you the correct trail. Many builders go by the rule of 2" of trail, but I find that with a shallow head tube angle, you get too much wheel flop. Papa says he prefers 0 trail on a bike, and I believe he said 1/4" trail on a trike. I set mine up with 1/4", which will increase to 3/4" when I install the 20" wheels. That will be fine with me, because I checked it out first, and found the wheel flop to be negligible at 3/4", and unnoticeable at 1/4". I believe there is a thread in the "Discuss your Projects" forum that deals with steering geometry. I had 2" of trail on my Meridian, and there was a considerable amount of wheel flop, which caused very twitchy steering at low speeds.

gbbwolf
06-24-2008, 09:21 PM
Yeah I kinda goofed on mine I set the bucket under the boom at 13 inches
It was eleven then I moved it to play around a bit and forgot to set it back.

Live and learn, Don't build bikes after you have been up for 20 hours,with no sleep.....

Nelson

P.S. I am riding it this way when I get it done.
If it is way out of control, I will have to cut and readjust.

SirJoey
06-24-2008, 10:14 PM
Well, I understand about trail, fork rake & all that. I'm using a beefy, tubular, straight fork that I can't possibly bend, so it seems to me that a 58 degree angle with a straight fork, would give me a monstrous amount of trail! Seems to me that even the "standard" 72 would still have quite a bit of trail when using a straight fork, so I'm thinking it needs to be about 75, to get the trail down to a reasonable amount, right?

Even though it's a trike, I don't want the wheel to flop over every time I take my hands off of the bars.... :eek:

http://img384.imageshack.us/img384/7131/sirjoeysigmedij1.gif

robertwb70
06-24-2008, 10:56 PM
I have a jig I use to set the trail easily- it just holds the fork at the same level as the wheel would and I put a broomstick or piece of threaded rod through the center tube of the fork where it will point at measurements marked on the base of the jig indicating the trail- then I can either measure the angle with an angle finder or just build the bike to the head tube while it's on the jig.

I'll try to post a picture tomorrow- it's really just some old bed angle iron I welded up in about 15 minutes but it makes this part of the design really easy.

SirJoey
06-24-2008, 11:02 PM
I have a jig I use to set the trail easily- it just holds the fork at the same level as the wheel would and I put a broomstick or piece of threaded rod through the center tube of the fork where it will point at measurements marked on the base of the jig indicating the trail- then I can either measure the angle with an angle finder or just build the bike to the head tube while it's on the jig.

I'll try to post a picture tomorrow- it's really just some old bed angle iron I welded up in about 15 minutes but it makes this part of the design really easy.

Kool, I wanna see it!

http://img384.imageshack.us/img384/7131/sirjoeysigmedij1.gif

TheKid
06-25-2008, 02:53 AM
On the straight forks, you can either cut a wedge in the legs, then bend and weld them, or make new dropouts that extend forward. On the hauler, I did both.

gbbwolf
06-25-2008, 03:47 AM
Yeah I never thought about cutting off the dropout's.
And making Longer ones.
I have enough bend in my forks now.
But new dropouts might work.
At least if it does not I wont lose much.
I have Plenty of those same forks.
And some 3/16th steel flatbar I can Cut and weld in for drops.
Or I may fabricate some square tubes Like you did.
I can ride on the one I got and work on a modded square set in my spare time.

Thank YA

Nelson

TheKid
06-25-2008, 04:42 AM
I posted this in your DW thread, but here goes: You could also just change thge front tube angle without too much trouble, 1/4" more upright should do the trick. If not, changing the dropouts is pretty easy, a lot easier than building a fork. The only reason I built mine, was because I had no other fork to use except a suspension fork, which according to most hub motor manufacturers, isn't recommended with their motors.

robertwb70
06-26-2008, 11:42 PM
Took some pictures of the jig with a fork mocked up to show how it works. It's pretty simple but I haven't seen any other jigs that do the same thing.

http://tinyurl.com/4wwlle

TheKid
06-26-2008, 11:52 PM
Excellent. Simple, effective.

SirJoey
06-27-2008, 11:41 AM
Quite clever, Robert! I love it! There's just one thing wrong with it...

...it makes more work for me, cuz now I gotta build one, LOL! :D

Thanx for posting it.

http://img384.imageshack.us/img384/7131/sirjoeysigmedij1.gif

n9viw
06-27-2008, 01:46 PM
+1, Cle-vah! Good work, now we'll all have one! :D

gbbwolf
06-27-2008, 10:38 PM
Will build mine once the wolf is done.