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Author Topic: Girder Forks.  (Read 77908 times)
Olds
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« Reply #120 on: September 29, 2013, 10:59:19 AM »

Sorry,  but can't see the problem. Huh
I am not altering the rake angle of the frame which is actually 41degrees 30 minutes.
The greater the rake angle the greater the ground trail. This can be reduced by using yokes with a greater offset, 'raked yokes' or using forward axle forks, all of which push the axle line forwards. Girder forks also tend to do this because of the length of the links. The rake of the forks is not dependent on the rake of the headstock but rather on the relative horizontal positions of the upper and lower pivot. By adjusting the lower pivot point forward or back I can change the rake of the forks (not the frame) to achieve the required trail.
« Last Edit: September 29, 2013, 09:33:58 PM by Old Newbie » Logged

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stumpy
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« Reply #121 on: September 29, 2013, 11:29:08 AM »

no problem mate im here to learn i think your forks are a work of art the off set looks quite large and i was expecting you to say the trail had increased
41 degrees of rake would explain 159mm of trail at present then you say you hope to have 41mm now
there is no problem mr ON ... like most topics on here folk are in search of input or knowledge im not having a pop at your work merely trying to understand for my own projects
please take it as a compliment not a criticism and look forward to you road testing it  Grin    
« Last Edit: September 29, 2013, 11:31:18 AM by stumpy » Logged

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Olds
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« Reply #122 on: September 29, 2013, 01:32:57 PM »

Sorry stumpy, wasn't suggesting you had a problem. You just made me think that there may be a problem with my own logic and to be honest, it's been so long since I had to do this sort of thing, doubts creep in.
« Last Edit: September 29, 2013, 03:58:56 PM by Old Newbie » Logged

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ByzMax
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« Reply #123 on: October 04, 2013, 11:01:51 AM »

Nice Job ON.

The only issue with the trail that you need to watch out for is when braking the front does not dip too much. This reduces the trail and often into the negative area as the headstock height and angle changes as it is pivoting around the rear axle .

On trikes it's usually ok though as the handlebars are normally long enough to stop you going into a tankslapper due to the leverage you have.
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Olds
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« Reply #124 on: October 04, 2013, 02:41:36 PM »

That is one concern among many.
Hopefully with the small amount of suspension travel expected, we should not quite get into a negative trail situation.
In making the bottom pivot adjustable (sort of) I can change the trail to overcome any handling problems that arise.

The tight bushes I mentioned earlier, turned out to be a slightly bent shaft, caused by welding on the lower shock mounts. Not enough to notice but required some (a lot) heat and a little (a lot) of persuasion to straighten. Embarrassed
« Last Edit: October 04, 2013, 02:44:01 PM by Old Newbie » Logged

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Olds
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« Reply #125 on: October 07, 2013, 06:43:18 PM »

Will soon get to the point where I can go no further till I can assemble the forks on the trike.
Turned up the outer thrust bearings/washers today and hopefully will get around to the inner ones soon.

« Last Edit: October 07, 2013, 06:50:15 PM by Old Newbie » Logged

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Olds
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« Reply #126 on: October 07, 2013, 06:46:41 PM »

I also decided to have a go at bending the new handlebars. 25.4mm x 3.24mm wall  CFS tube, annealed where the main bends are. These are 38" wide 14" pullback with a 2" rise. Not entirely sure if I like them.  Undecided

« Last Edit: October 07, 2013, 06:50:39 PM by Old Newbie » Logged

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Baychimp
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« Reply #127 on: October 07, 2013, 07:00:21 PM »

I recon they will look alright Dave,once you have mounted them up.
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Olds
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« Reply #128 on: October 08, 2013, 11:16:39 AM »

Thought the straight centre section was too long, so I had another go
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Getting older but no wiser! Just using bigger hammers.
The answer to most problems, fire and lots of it.
Olds
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« Reply #129 on: October 09, 2013, 07:39:15 PM »

Decided add built in risers to the handlebars rather than use Flanders as intended. Still have a couple of hours of weld smoothing ahead.
Trying hard to get a vintage look/feel about them
At the moment these are free to rotate, so I can adjust the angle of the bars once everything is assembled.
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merv
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« Reply #130 on: October 09, 2013, 07:57:32 PM »

nice looking bars
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Olds
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« Reply #131 on: October 16, 2013, 12:43:18 PM »

Thanks.
Being this wide they do look a bit thin but I will see how they look once painted.
Assembled everything up on the bench today and all seems OK. Next on the list is the headlight mounting.
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Getting older but no wiser! Just using bigger hammers.
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twisted
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« Reply #132 on: October 16, 2013, 02:15:09 PM »

looking very tasty ON  Wink.
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hornet6
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« Reply #133 on: October 16, 2013, 05:27:21 PM »

Going slightly off on a tangent here....but seeing as you lot are way ahead of the game on girders and suspension set ups. Do you think this set up would work ok....it looks simple enough. Huh Huh
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spanners
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« Reply #134 on: October 16, 2013, 07:07:35 PM »

Going slightly off on a tangent here....but seeing as you lot are way ahead of the game on girders and suspension set ups. Do you think this set up would work ok....it looks simple enough. Huh Huh
leading links or ,earls, forks as they were once known  i had them on a DOT trials bike years back  some even had bent/curled forward stanchions and were commonaly called ,,,banana forks,,,
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