The Chopper Compendium

I have ordered hardware for front end!!

It will be here tommorow!!

Here is a print and I belive the final linkages layout???

Anyone see any problems???

I know I am getting anoying with all of this!!!

I went to check the simulator and found it did not really match???


I rendered this in a 2d cad???

See any problems or want any measurements???

here is the front end rules
http://www.choppercompendium.com/ccforu ... f=34&t=494

Rule of thumb for setting trail of hydraulic and girder frontends:
First use the tire width formula (T=(((rear tire width/front tire width)*100)-100)*0.01) to find the needed adjustment trail.
I.E.: 90/90/21 front tire and 250/35/18 rear tire
T=(((250/90)*100)-100)*0.01
T=(((2.778)*100)-100)*0.01
T=((277.778)-100)0.01
T=(177.778)*0.01
T=1.778" of trail adjustment needed

* remember this equation results in American Standard Measuring not metric so you would have to do one more little conversion for metric: simply multiply answer by 25.4 to get mm answer
* i try to round to three decimal places as that is a common amount when machining.

So now using a baseline trail of 2" I will add the trail adjustment to the 2" baseline and come up with my needed trail.
I.E.: 2" + 1.778"= 3.778" of needed trail or round to nearest 1/8" so 3.75" of trail.

- I do not concentrate on wheel flop for these front ends as they respond better to the trail numbers rather than the wheel flop numbers. Frontends with a rocker system at the axle, I use my wheel flop equation and shoot for .125" of trail as the axle travels in an arc about the fulcrum point.






Hello krymis have I done this right???



3-21in front = 80/100/21
4-18in rear = 100/100/18
http://www.cb450stuff.com/tires/




So

T=(((100/80)*100)-100)*0.01=19
T=(((19)*100)-100)*0.01=18
T=((18)-100)0.01= -0.82
T=(-.082)*0.01= -0.0082
T=- -0.0082 of trail adjustment needed????????



So I need to be shooting for 2in instead of 3.5in????






Here is my flop number if I did it right at 3.5 trail??? This is actual trail not ground trail???


(((3.5 * sin(45°)) * cos(45°)) / 90) * 40 = 0.777777778


And the flop for 2in???

(((2 * sin(45°)) * cos(45°)) / 90) * 40 = 0.444444444

3-21in front = 80/100/21
4-18in rear = 100/100/18
http://www.cb450stuff.com/tires/
So
T=(((100/80)*100)-100)*0.01=19
T=(((19)*100)-100)*0.01=18
T=((18)-100)0.01= -0.82
T=(-.082)*0.01= -0.0082
T=- -0.0082 of trail adjustment needed????????
So I need to be shooting for 2in instead of 3.5in????
Here is my flop number if I did it right at 3.5 trail??? This is actual trail not ground trail???
(((3.5 * sin(45°)) * cos(45°)) / 90) * 40 = 0.777777778
And the flop for 2in???
(((2 * sin(45°)) * cos(45°)) / 90) * 40 = 0.444444444[/quote]


your math seems to be a little off
80/100/21 use the 80 for the front tire
100/100/18 use the 100 for the rear tire

so,
[{(100/80)100}-100]0.01
[{(1.25)100}-100]0.01
[{125}-100]0.01
[25]0.01=.25" of adjustment

2"(base trail)+ .25"(adjustment)= 2.25" of adjusted trail

now using an adjusted trail of 2.25" and a rake of 45* to get wheel flop factor
[{(2.25)(sin45)(cos45)}/90]40
[{(2.25)(.7071)(.7071)}/90]40
[{1.12498}/90]40
[.012498]40=.4999" of wheel flop

so to sum up: 2.25" of adjusted trail with a wheel flop factor of .4999" at a 45* rake angle.

If you would like to, you can use the easy method for trail. If you can do the real trail # that would be better. However the difference between real trail and simple trail is very little.

Thanks!!!

Maybe you could help me with a way to formulate the real trail???

Wheel diameter + tire I have read for a 21in wheel is normal 27.60???
I would have to measure contact patch or is there a known number????

I have been using the simple trail right???

Excuse me for being a dounce!!!

and Thanks Again!!!

if you use simple trail keep doing it. you really are not far off (less than .125" in most cases). At the end of the day don't worry too much about the trail or the wheel flop. I made these rules and formulas to hit a good starting sweet spot. I always like playing with frames and front ends so i just figured i would post my findings.

Thank You!!

With the way I have streched and lowered this frame I will most likley not have much room for error???


Here is CAD of adjusted rake!!

I will have a built in rake in trees of 3 degrees!! With minimal flop factor!!

Girder Legs will be at 48 degrees!!


I now know linkages and proper trail and length of all girder components!!







Thank You Kyrmis!!!

I have no experiance with these being just a young punk kid!!!
Thanks!!!

looking awesome. that is what we like to see. On the girders you want to find the arc sweep of the axle along a 40* segment, 20* up 20* down. Find out what your wheel flop, rake and adjusted trail are.

Thanks Again!!



I keep looking out the window for the hardware!!!

Soon as they come I can start assembling and checking measurements of all componets!!!

Then start making the parts!!

I have about as much time in fighting my way thru engineering the girder as building the whole frame!!!

Looking good Man & welcome to the Site Man.

Thanks and It is NICE to be here!!





I got started steering my girl my girl!!!


I got the planned machining of the trees done!!

We will see with fitting if any more machining will need done???


I started by fly cutting the plates down to 1.750 thickness I wanted from 2.00in!!!!
This took awhile!!!














The two plates at thickness!!

















Then used the infamous 30mm drill bit to drill hole in top tree!!!

















Then used 15/16in bit to drill bottom tree!!

















Then threaded 1in 14tpi!!!




















I then drilled the clamp bolt hole in top tree and ran 1/2 13tpi tap down as far as it would go so I could hand thread latter!!!





















Then drilled the two holes one each plate for the linkage bolts!!!
































These bolt wil be cut to size and threaded on both ends later once sure proper length!!






















Then slotted for the shock!! I decided to run just one!!
I decided to cut this direction so I would not have any sharp corners to avoid cracks and breakage latter!!
















Showing how well shock fits!!!
I will turn a piece of steel and put inside the rubber so shock will not be a structural part when tightening the legs down!!





















Then put recess in for the shock clearance!!!


















Showing the shock inserted!!





















Showing shock has enough movement if the forks leave the ground!!!!





















I then used a known angle gauge and made clearance for upward movement!!
































































Then drilled the holes for the handlebars!! Then used 3/4 endmill to recess the bolts!!! While testing depth!!!















































Then clamped on rotary table to put the curves in top tree!!





































Then used grinder to cut for the clamping part that will fix the top tree!!!





















Then hand sawed the rest of the way thru!!
I also used a sawsall after to open up it a little farther!!!























I put it back in vise and used the drill bit to drill the clamping hole to line it back up!!

Then used a 1/2 endmill to drill thru shoulder side of plate!!
I used the saw blade to know when I was to the other threade part of plate!!!














Then 3/4in endmill to recess the bolt head!!



































Then fly cut the top tree to clear the backbone!!!

















Then put curves of bottom tree!!

















The two trees done!!
Top














Bottom!!!
















Set on top each other!!!

















I also have 3/4 of the steering shaft done!! It is turned to size and theaded for the bottom tree!!!
After 18hrs straight machining only stopping to eat and the ocasional planning session I am taking a break!!!

nice

Very nice to see your progress.

Couple things, drilling the corners to prevent stress cracks was new to me, but I think it's a damn good idea.
I'm not a machinist, haven't even played one on TV, but it sure seems reasonable to me.

I'm wondering what kind of bender you're using that you can get those long radius bends, like the backbone.
They look really good.

A great thread all around...