Author Topic: Chop Friction...or...Bobber by comittee (Read 6969 times)

kerryb · « **on:** October 15, 2009, 05:38:57 PM »

I always wanted to build a bike, so I collected a couple parts bikes and took 'em apart. After staring at the stuff for a couple months, reading this forum a lot (inspiration) and riding the one that works to keep my grin on... here is the result.

I could do this the usual way...in my shop by myself till I gave up or accomplished an acceptable result. But it would be more fun to discuss the vagaries of the current state of bike mangling while deciding how to proceed. I've never built a motorcycle before. Heck I've never cleaned a set of carbs...the worst that can happen is try again.

So the plan is to build a bike governed by the premise that form follows function, cool is in the eye of the beholder, and he who holds the saw, gets to guide the cut.

So join in if you want, express your opinion if you dare, but be nice, cuz the computer is in the kitchen and the MiG is out in the shop with the remains of the day....he he!

mystic_1 · « **Reply #1 on:** October 15, 2009, 06:26:47 PM »

Nice lines!

I think yours is one of the first hardtail frames that I have seen which keeps the triple backbone arrangement. Got plans for sheetmetal yet?

mystic_1

Industrial Rat400f Killer · « **Reply #2 on:** October 15, 2009, 06:39:22 PM »

I like where your at so far.

kerryb · « **Reply #3 on:** October 15, 2009, 08:34:11 PM »

Yes Mystic1, the plans for the sheetmetal are to reuse the stock '78 fuel tank and fenders, but to reshape them to fit the new form direction. The tank specifically needs to be narrowed at the tail to fit the narrow waist frame. The frame was hardtailed to lower and narrow the seat area so I could stand over the bike with my heels on the ground.

Tonight I started making brackets to mount forward controls. When those are further along, The placement of the seat can begin along with some exploration of what handlebars will give a comfortable riding position.

The triple backbone was to keep some semblance of rigidity in the neck area. This is intended to be a nimble bobber that can be ridden hard and not be "wiggly".

Thanks for the encouragement Rat, it took a lot of head scratching to get this far.

Ogri · « **Reply #4 on:** October 17, 2009, 02:19:09 PM »

Looks very good, natural, like a hardtail frame the factory would have offered (in an alternative reality.) I like the way you haven't stretched the back tooo much.

Does the motor have stock ground clearance? The front downtubes look original (unstretched), and the motor appears level (so you haven't dropped the back end - apparently).

mystic_1 · « **Reply #5 on:** October 17, 2009, 02:27:08 PM »

If I might make a suggestion....

Take the swingarm pivot bolt and the swingarm pivot collar, and reinstall them in the stock location. Make a collar to cover the pivot tube if you want out of some suitably sized tubing or just paint the collar.

This will have the result of tieing your frame together from side to side right behind the motor. That should keep things nice and tight back there and take some stress off your motor mounts.

I presume you have plans for a rear fender crossbrace when the time comes, to tie together the rear of the frame?

The more I look at your frame the more I like it. What's up with the welds at the top where everything meets? Looks complicated.

mystic_1

kerryb · « **Reply #6 on:** October 17, 2009, 08:00:51 PM »

I didn't realize how deceiving the pics could be...so a little background is in order. The rear triangle was created around the original rear dropouts and then the swingarm was cut away and removed. This allowed the rearend to be built in a "dropped" position while retaining the stock wheelbase. The tripleclamps were then slid two inches down the fork tubes to get the original frame tubes level. Ground clearance is now about 7 1/2" to the oil pan. The top tube welds evolved in sequence as the tubes were built, with the last two being from the upper rear engine mounts to the top central "waist".

Mystic... I tried the swingarm-pivot-tube-thing, and I think a cross-tube welded on above the upper rear engine mounts might give better strength and keep those new joints from spreading and flexing. There are still many gussets to make and weld in. My welding is getting better...I'm concentrating on strong...pretty will come with time.

Retro Rocket · « **Reply #7 on:** October 17, 2009, 08:23:34 PM »

Nice frame, i don't generally like modded standard frames but that one looks very good. I have an old slightly damaged K2 frame that screaming for something like this. Where you have the 2 bracing rails under the main frame, do you think it possible to make them one piece all the way to the swingarm pivot, then weld in the middle to the top frame rail? And what type of tubing are you useing, thanks.

Mick

kerryb · « **Reply #8 on:** October 17, 2009, 08:56:52 PM »

retro...yes, the central vertical support could be a single tube down to the swingarm pivot, like an early harley frame. I gave that a lot of thought, but chose this way to keep the rear motor mounts in a cage-like configuration. This also made alignment easier because I welded braces around the motor area before cutting away the rear triangle parts. The tubing is 1" diameter x 1/8" wall continuously welded tubing (not pipe). This frame is actually practice for the next one which will be drawn-over-mandrel tubing which has a higher tensile strength. I'm gonna put it all together, ride it around the block a few times to be sure I like it, and do it all again with better materials, more welding experience by then, and correct the mistakes that come with this type of adventure. For now...I'm just havin a ball!

blindguy76550 · « **Reply #9 on:** October 17, 2009, 09:34:28 PM »

that is a sweet machine.
i am working on my first as well and already see things that are going to be different on my secound one wich is waiting for the finish of the first. my frame is going to be similar to yours on the secound bike. let me know how the tank works out for you.
see ya round,
da blindguy

Retro Rocket · « **Reply #10 on:** October 18, 2009, 01:44:43 AM »

Quote from: kerryb on October 17, 2009, 08:56:52 PM

retro...yes, the central vertical support could be a single tube down to the swingarm pivot, like an early harley frame. I gave that a lot of thought, but chose this way to keep the rear motor mounts in a cage-like configuration. This also made alignment easier because I welded braces around the motor area before cutting away the rear triangle parts. The tubing is 1" diameter x 1/8" wall continuously welded tubing (not pipe). This frame is actually practice for the next one which will be drawn-over-mandrel tubing which has a higher tensile strength. I'm gonna put it all together, ride it around the block a few times to be sure I like it, and do it all again with better materials, more welding experience by then, and correct the mistakes that come with this type of adventure. For now...I'm just havin a ball!

Excellent Kerry, Actually i just reread your reply, i meant the 2 support struts under the central strut.They could be bent to go from the front all the way to the axle in one piece, then weld everything to them. Hope you don't mind me pinching some of your ideas, i really like the way it looks. I was thinking maybe, when the unused parts of the frame are cut away,to bend the front down tubes to make use of the extra fork length and slightly rake the front out a bit, and also make it a straight line from steering head to the axle..what do you think?

Mick

kerryb · « **Reply #11 on:** October 18, 2009, 06:35:18 AM »

Wow! That's a lot to think about! Some time ago there was a custom frame built for the "Horse" amateur chop-off that had that configuration, a la Schwinn bicycle cruiser frame. That would be real cool, but I don't have building jig to work with so the alignment would be "iffy" at best. I'm still trying to figure out how to rake the front end out to use up the extra 2" of stock fork tube. I think that would be easier than shortening the tubes, and I get to keep using the stock parts, which was part of the original premise in the design. The other danger with changing the front rake is changing the handling. I don't want to lose sight of "nimble"

The gas tank is going to be a side epic of it's own. I read that the metal is thin...I'm not a sculptor... no english wheel yet...but I do have two extra tanks for reassurance.

if you use my ideas that would be a great compliment...make me feel good, show us.

Retro Rocket · « **Reply #12 on:** October 18, 2009, 03:22:18 PM »

Quote

I'm still trying to figure out how to rake the front end out to use up the extra 2" of stock fork tube

I was thinking that {if it can be done without altering the integrity of the tube} that maybe where the front down tubes meet the brace {about where the front frame tubes passes the tappet cover} it may be possible to heat and bend the down tubes back slightly to increase the rake and also make the top frame rail into a straight line to the axle. It would extend the rake and straighten the backbone, which would kill 2 birds with one stone.....

Does that make any sense?

Mick

kerryb · « **Reply #13 on:** October 18, 2009, 06:18:32 PM »

Hmmmm...OK...lets see....
1. this must be done before the rear triangle (are they called seat stays on a MC frame?) are bent and installed, the three tubes coming back from the head tube are modified. The main tube is bent down, to form a straight line with the rear axle by bending the down tubes up front.
2. the lower two of the top three would need to be raised slightly to maintain space above the engine and carbs for clearance of the throttle linkage.

3. The heat and bend sequence would take place where a lot of metal is (the bracing for the neck) and would require careful alignment. Currently I don't have a jig or measurement table to keep it all straight. I suppose if you could get the same amount of heat to both tubes, they would bend evenly...I don't see that happening with my crude equipment and techniques.

We gotta work out a better way. I saw a post of someone who cut the neck right behind the steering tube, bent the neck, and welded in plates to fill the gap. alignment again!

I gettin a bald spot from scratchin my head!

Retro Rocket · « **Reply #14 on:** October 18, 2009, 06:33:40 PM »

Quote

I gettin a bald spot from scratchin my head!

Thats the fun part, working it all out...

What i was thinking was, to do what you have said about heating both sides , then using a hydraulic jack slowly bend the neck back, it wouldn't need to be bent much if you look at your pics, but i think its doable. The frame would have to be pretty well secured so the jack could work properly but i think i would rather try this method than cutting the neck area. Or alternately the down tubes could be cut and a piece added each side then braced and welded back up....I love the problem solving part of construction....

Mick

blindguy76550 · « **Reply #15 on:** October 18, 2009, 07:27:09 PM »

i have always heard that heating and bending metal weekens metal, hmmmm?

??

Retro Rocket · « **Reply #16 on:** October 18, 2009, 07:44:10 PM »

Quote from: blindguy76550 on October 18, 2009, 07:27:09 PM

i have always heard that heating and bending metal weakens metal, hmmmm???

Yeah it can but it can also be treated to retain its strength. Cutting sleeving and welding may be better. Just as well we both have old frames to test it out on.

Mick

blindguy76550 · « **Reply #17 on:** October 18, 2009, 07:47:51 PM »

cool let me know how it goes, cause i never thought of doing that.

kerryb · « **Reply #18 on:** October 19, 2009, 08:48:41 PM »

It's time to move on...we can go back to frame design during final analysis.

What comes first? The seat, pegs, or the bars? I didn't buy a Dyna wide glide cause I couldn't reach the pegs comfortably (another childhood dream squashed) the dealer said they couldn't be moved.

I guess the pegs come first. They will be forward controls so I'm not folded up in a squat to ride it with the lower seat.

Then the seat can be located close enough for comfort (a little bend in the knee). Once the seat and pegs are on, bars shouldn't be too hard to figure out.

I never knew you could cut 1/4" steel plate with a handheld jig saw...this is getting easier!

manjisann · « **Reply #19 on:** October 19, 2009, 09:12:18 PM »

Sorry, nothing constructive to add, but diggin the lines. I would live to try this some day, so I wanna tag along.

Brandon

Retro Rocket · « **Reply #20 on:** October 19, 2009, 09:16:15 PM »

This is the kind of look i will be going for.....

I love the look of the exile bikes.

It will be a while before it is actually started though because i am building another bike at present and are trying to sell my property up north and buy a new home...

Mick

kerryb · « **Reply #21 on:** October 21, 2009, 04:40:55 AM »

Oh I love the "Exile look" too! You are jumping ahead though. How fat can I make the front tire with stock rims? Can I learn to ride a foot clutch with a 1-down transmission? And...a question soon to be answered...Will the reach on those bars be comfortable with the seat that ends up on the bike.

Speaking of seats, I have a cool old tractor seat pan to cut down and put springs under.

Manjisann...don't wait, start now, I had to go through a horrible illness before I realized "life is short...do it now...tommorrow may be a whole new story line.

Spikeybike · « **Reply #22 on:** October 25, 2009, 05:38:31 PM »

i'm diggin it man , definitely think you should go the "big tires" route

i don't think heating the pipes and bending them will hurt the metal , as long as you don't quench them (pouring water on hot welds, for the layman)
the only problem i see is setting up some sort of jig to make sure it bends where you want it to ... but it's not impossible

keep it up, looks great .. and as i always say "if ya can't find it ... make it"

Spikeybike · « **Reply #23 on:** October 25, 2009, 05:47:05 PM »

or you could just brace everything. cut them off and use miter cuts .. then just grind everything smooth

just a thought

Ogri · « **Reply #24 on:** October 25, 2009, 05:56:09 PM »

I'd visit a chopper forum before you start bending tubes. There's a lot to learn. It can be done without an expensive tube bender but I think you'll need to pack the inside of the tubes with wet sand or they'll flatten when you apply pressure.

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Author Topic: Chop Friction...or...Bobber by comittee (Read 6969 times)