newbie xs 6-fiddy chop

sluginxlt

sluginxlt

xs6-fiddy
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westland MI
ive been getting the urge to build a bike and finally scraped up some money to get a patient. here she is 79 xs650 plans are to build a custom 4-5" stretch drop seat hardtail, a slight rake, sportster tank, make some custom pipes, paint the motor black with polished odds and ends, and possibly jockey shifter with foot clutch.
heres how i bought her saturday. shes stripped down today but didnt take a pic.
bike021.jpg
 
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heres a little update, a week later its nothing but a garage full of junk. ive been working on the hidden axle plates at work, picked up a 94 sporty tank in great shape today for 40bux.
oh yeah and thats a 45* rake via zip ties lol, just getting an idea of the look. gonna try and get it jigged up and tacked to the table for the hardtail in the next couple days here.
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bike019.jpg

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Welcome to the site! Looks like you're wasting no time. What are your plans for the re-rake as far as how you're going to do it?
 
yeah im making hidden axle plates. just slotted the 3/8 plate and cut it to size today, ill tig weld them in on my lunch break tomorrow. then i just need to put in the adjustment bolts
 
Travis said:
Welcome to the site! Looks like you're wasting no time. What are your plans for the re-rake as far as how you're going to do it?
Click to expand...
im gonna brace everything in place then cut the whole neck off taking out a few inches of tube with it. then im gonna get a new peice the same size for the top tube but 1" longer and contour it to the desired rake angle and weld it in with a slug joining the new 1" longer tube into the back bone. as for the bottom tubes its up in the air of either adding an elbow to them for a goose neck, or going with a whole new single down tube. "made sense in my head" lol.
 
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I got a little progress today, finished the hidden axle plates on my breaks at work, came home and got the frame jigged up, and got to some cutting!
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well its freezing out but im still pecking away at the bike. i ordered the 1 1/8" dom tube for the hardtail and itll be in on monday, but in the mean time i was practicing on the bender with some plumbing pipe because i dont wanna play around on almost 100 dollars worth of tube, but heres the mock up pic with the plumbing pipe. also im working on a seat with a tube frame and 2 seperate pans... ill get some pics of it when i finish the main frame of it monday.
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made some progress, got the hardtail almost done just have to machine the a slug for the bottom of backbone and weld it in tomorrow. ofcoarse i couldnt pick a more simple tube design to bend but thats what i wanted it to look like but the harbor frieght bender put a some little dents from the die in the tubes, but i did pack them with sand so they didnt flatten or kink, looks like powder coatings out of the question cause there gonna need a skim coat of filler. threw the seat frame in the pics just to get the image, still need to make the pans for it "its just card board in the pics". what do you you think so far?
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If you have kinks in the tube then it is weakened and should not be used, the design of your hard tail with the bends down, (especially with the kinks), allows for the stresses from the down force to buckle your frame.:yikes: You may have some way of combating this :confused: Do you have the qualifications to understand what you are doing as this looks to me to be very dangerous. Sorry to be blunt but your life could very well be at stake if you intend to ride this
 
theres no kinks in the tubes just some little dimples from the die sitting on it angled to make the compound curves on the upper tubes. i understand what your saying about the frame design not being as strong as straighter higher mounted upper bars but i wouldnt think it wouldnt buckle with the weight of me and the motor unless i took it out jumping hills. i planned on adding some gussets to it, any suggestions on strengthening it up with the tubes that are there?
 
If the hard tail was strengthened the weight would be transferred to the engine frame and as the top rail intersects a 3rd of the way down the stress is transferred to the single vertical tube. That is why the hard tails intersect at the top of the downward bend. ....................Imagine an upward force on the headstock and an upward force on the rear wheel, (made worse because of no swing arm and shocks), the weight of the bike and rider is the downward force accumulating where the top rail (hard tail) and the vertical tube (rear of engine) meet.................as your hard tail is bowed down, the upward force (stress), of the rear wheel and head stock is spread between the bottom of the curve on both the top and bottom rail (as the tubing is already bowed down the tube has lost a lot of strength),and the intersecting point of the top rail and the vertical tube ...............Because your top rail intersects down the vertical tube, if you brace the hard tail, the upward force from the rear wheel and headstock is transferred as a horizontal stress against the vertical tube alone.

I am not an engineer and this is the way i see it if any one else can shed a light on this to verify or discredit :eek: my opinion pleas do
 
giving a quick look, i agree. it looks like it might be helped by triangulating up to the main cross bar, transfer the forward loads into the top rail. the curved shape of the hard tail will also want to collapse in on itself. the tube is much stronger in compression than in flexion, in this configuration, the top tube of the tail intersects the axle on the side and not at the end, with all the force tending to bend the tube, and given that the tube is already bent, it'll be easier.

i'm probably not explaining this right, and haven't done the math, the bending strength of the tube might be sufficient, but i wouldn't risk it without triangulating the heck out of it. think of a steel bridge, that kind of structure is what you would need, and like i said before, you'll want to brace it to the top member, which will transfer the loads down to the front wheel (the top member takes pretty much all the weight of the bike in compression, when you think about it).

if you like, i could try sketch up and scan what i'm talking about...

(and i'm not an engineer, just an engineering technician, hoping to go back to school to get that bachelor's in the fall...)
 
I think it looks awesome and plenty strong.. Triangulating the shit out of the whole thing is going to ruin it.

If this thing is holding together strong, you should be fine.
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And this this hasn't killed him yet, you'll be fine.


Make sure your welds are good, and I'll think you'll be okay! Maybe do pre-ride weld inspections to check for problems once in a while.

However, in the event of death or injury to yourself or others because of my "internet advice", I must also post the following disclosure:

I can not be held responsible for the injury or death of anyone as a result of my "that looks safe to me" advice! :D

Nice build by the way! keep the pictures coming! How about some close ups of these dings in the tubing. What size and grade of tubing are you using? 1 1/8" .120" wall 1020 DOM?
 
Travis inn the first pic the bows in the tubes on the hard tail oppose each other and the top strut is braced with a gusset brace on the bottom tube near the motor and also has what looks to be something clamping the top and bottom tubes together along from the axle pullers, all in all well braced. As for the video clip, i guess time will tell :laugh:
 
Well seeing as how you know what i am going to say before i am going to say it we might as well be married :laugh::laugh::laugh:
 

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