MY 1978 XS chopper/ Custom

[roccet]

here is the fix to that..
its now 2.75 inchs and can get it to 5.1 with a little tweek with out any issues.
I went the wrong way before.. Thank you PEEPS for spotting that out.. i had my terminology backwards. Thank you for straightening me out.. and Thus the reason i have been posting this thread..
XS11 For life!!! I like the adjustable of this system because i can get it right where i want it pretty easily and be able to play with my trail . My goal will be 5.1" trail

[DGXSER]

WHEW!!!! OK, you updated the image. Yep, your on the right TRAIL (pun intended) now!!

[jwhughes3]

that looks better

I think it will actually make the wheel look stretched out though in reality it won't be...

Nice...

I'm glad there's a safe way to lay it out because it looks so radical it just begs to be ridden!

John

[roccet]

by playing with this from all the comments i was actually able to be a bit more travel in my suspension as well so that was a plus...
I designed this so it fit together like legos .. if i didnt like the fit or look or size
i can change it out quickly. looks like it paid off already because now im able to remake a couple pieces pretty easily and get this thing on the road.

Now i just need to decide on a decent headlight..

[crazy steve]

Yep, that's way better...

One last comment about trail; those low trail numbers that guy was mentioning can be ok. But to safely use low trail numbers, you need more rake in the neck. That's the main reason for reducing trail; as the neck rake goes up, stability gets better but steering effort and responsiveness goes out the window. Because of the different 'leverage' you're seeing with increased rake, less trail isn't as big a deal. But with a 'standard' rake of 26 to 32 degrees, too little trail is a bad thing...

[fredintoon]

either that picture changed or my mind is older and more feeble than I thought. What I see now shows positive trail. Not a lot, but some.

Hi Don,
betcha Mr Sneaky changed his graphics but was too embarrassed to 'fess up.

[DGXSER]

Thanks for the support of my visual accuity Fred! I am guessing he uploaded the new image with the same name to where he is storing it but did not realize it would change it here. (I'll give him the benefit of the doubt on that one).


The more I look at it though it does have alot of bolted up components in some pretty substantial shear force locations. Thinking about bending moments and such, those will definitely need to be some pretty stout fasteners. I believe Tony is evaluating that and accounting for it. Mr. Cautious here would be hesitant of it though. I think I'd try to find a testing setup and put it through several thousand repititions of some reasonable occilations at force before I would throw in on my bike and ride.

Of course it would only make sense to try it out at some very low speed stuff to start with and see how it reacts.

[cowboybob998]

Off bace ?

i may be way off bace but the way i see it in that dwg. is as the frame comes down and the wheel goes up because of the rotation of the pivot of the wheel the trail will change as the the bike moves up and down makeing a bit hard to handel, i aint no engineer just an ol red neck.

[fredintoon]

- - - - Mr. Cautious here would be hesitant of it though. I think I'd try to find a testing setup and put it through several thousand repititions of some reasonable occilations at force before I would throw in on my bike and ride.

Hi Mr Cautious,
compare the drawing to the two lengths of skinny clamped together pipe that are the stock forks, eh?
Mind you, there's still room for improvement.
I don't like the wasp waist where the shocks attach to the fork legs. That girder should run straight with a lug stuck out where the shock attaches.
I don't like that the trailing links are individual pieces because that set-up can flex a lot. The links should be integrated into a single U-shaped piece around the front of the wheel.
And that fork is gonna nosedive unless the brake calipers have a parallel linkage to the fork beam instead of transmitting the brake torque to the suspension links the way it's shown now.

[crazy steve]

..And that fork is gonna nosedive unless the brake calipers have a parallel linkage to the fork beam instead of transmitting the brake torque to the suspension links the way it's shown now.

Fred's right about that; this is going to have bad brake dive without a link to transfer the torque reaction. That's not something you can fix with spring/shock rates either.

If this were reversed (leading link, rather than trailing link), the brake torque would help prevent brake dive...

[roccet]

WOW you guys are awesome.. I love the feedback.. some are really looking at this really deeply which i really appreciate..
I also like how honest people are being.. if they dont like they say.. and i really respect that.
>>>betcha Mr Sneaky changed his graphics but was too embarrassed to 'fess up<<<

Nothing to fess up to.. I changed the graphics base on my conversation about positive and negative trail. one of the original pics was up till i deleted it on my photobucket. I deleted all previous revs as to make sure im moving forward on my design.


Hi Mr Cautious,
compare the drawing to the two lengths of skinny clamped together pipe that are the stock forks, eh?

(skinny?? those are 1.75 diameter not skinny by any means and will remain
there until the rest of the pieces are fit properly)
when I get the pieces fit together properly they will be replaced by Bars are same size .. Basic rectangle part that will replace those round bars


Mind you, there's still room for improvement. (Its all proto type even at first ride then i will make my permanent changes)


I don't like the wasp waist where the shocks attach to the fork legs. That girder should run straight with a lug stuck out where the shock attaches.
I don't like that the trailing links are individual pieces because that set-up can flex a lot. The links should be integrated into a single U-shaped piece around the front of the wheel.
And that fork is gonna nosedive unless the brake calipers have a parallel linkage to the fork beam instead of transmitting the brake torque to the suspension links the way it's shown now.

>>>>>>>><<<<>>
All things I have been considering. as far as the lower arms go.. I found some material 1.75 x 4. thick instead of 1.375 Flex is defiantly not a problem

I am only mildly concerned about a couple things and flex is not one of them.
I agree with much of what your saying though. Nose dive im a bit on the fence about. I am working with another Aircraft engineer on this and are using some of the data we collected on a landing gear system we made some time ago . the force and direction are a bit different but some of the same principles apply.
We are thinking of linking the two lower arms together just as you said but not infront of the tire it will be roughly like a mountain bike style .. just over the rear of the shock. I really do not want to attack the look of the forks to much im trying to keep it simple.

[Pat Kelly]

i may be way off bace but the way i see it in that dwg. is as the frame comes down and the wheel goes up because of the rotation of the pivot of the wheel the trail will change as the the bike moves up and down makeing a bit hard to handel, i aint no engineer just an ol red neck.

The trail (and rake) change on telescopic forks too as the wheel goes over bumps and during braking.

When I was a kid we made our bicycles into choppers. Most kids removed the front wheel, then jammed the fork legs into the top of another set of forks. This created a set of forks twice as long as original. The bend in the forks was also doubled creating the positive trail illistrated in the earlier submission. On my bicycle, I had straight fork tubes with raked triple trees (looked cooler). Though a bicycle isn't as fast as a motorcycle, the handling charicteristics are the same. Even with the positive trail I could ride with no hands at any speed, around corner too. The one disconcerting effect was when you turned the bars to the right, the head tube would move left a bit. Took some getting used to but it was more stable the faster I pedaled.

[fredintoon]

- - - - (skinny?? those are 1.75 diameter not skinny by any means and will remain
there until the rest of the pieces are fit properly) - - - as far as the lower arms go.. I found some material 1.75 x 4. thick instead of 1.375 Flex is defiantly not a problem - - -

Hi roccet,
I meant the skinny 37mm diameter fork tubes of the stock XS11 tele-forks.
And the link bars themselves seem to sturdy enough as shown.
It's the assembly that will flex, not the links.
You have a bolt-up U-section made from 2 links joined by the wheel axle and whatever spacer tube you have between the wheel bearings while the whole thing pivots on the two bearings at the other ends of the links.
The flex will be in the joints, not the links.
Better to join the links into a fork around either the back or the front of the wheel so when the wheel is bolted in the subframe makes a box instead of a loop.

[roccet]

Hi roccet,
I meant the skinny 37mm diameter fork tubes of the stock XS11 tele-forks.
And the link bars themselves seem to sturdy enough as shown.
It's the assembly that will flex, not the links.
You have a bolt-up U-section made from 2 links joined by the wheel axle and whatever spacer tube you have between the wheel bearings while the whole thing pivots on the two bearings at the other ends of the links.
The flex will be in the joints, not the links.
Better to join the links into a fork around either the back or the front of the wheel so when the wheel is bolted in the subframe makes a box instead of a loop.

Oh yes , Im with ya. I will be doing that but honestly i think its overkill. I am just doing it as piece of mind and since i am getting some great feedback on this . At first go it was a thought but decided against it for looks but its better to be safe an go with the masses and there gut feel. Everyone involved in this thread is actually helping me design the last portion of this bike.

[roccet]

not exactly the same but i found a few ugly versions of what i am doing.
I also was able to view an old landing gear.. and there is very little difference.

I can almost hear the argument now saying there is a cross bar merging the bottom section. PRETTY WEAK excuse of one.
The is NONE on the couple of pieces that i found .. I will see if i can get a picture up of one. The aircraft guys squirm a bit when i ask for pics of things so we will see.