Full size custom pushbike springer progress shnaps

Discuss your bike, modifications etc.
Timbo
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Post by Timbo » Sun Dec 10, 2006 1:56 pm

This front end was alot more work than I expected, but here it is all tacked and bolted together.
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I'm going to weld the nuts on one end onto the cut axles on all the pivot points at the base of the forks then smooth em over for a cleaner look, hopefully I can lay my hands on some classy type of nuts for the outside then send em off for a chrome finish. These old rusty layabouts are makin this look like a paddock hack.
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The pre-tension adjustment on the top set of springs needed an extra spacer, I welded some axles within the tube but then didn't cut them at the right length, I forgot they needed to be under tension at full extention, anyway, they work really well with the spacer & doesn't look too bad after all. Even though it's only tacked, (there's not too much weight on the front itself with the seating position where it is) I took this out and rolled it up and down the street on the bumpy naturestrips, the front end was workin away with about 40 to 50mm of available travel, looked cool as from the seat.

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I'm diggin the profile of this machine again, the lines have to be right, and they are. I'm not too sure the whitewall idea is going to work, most characters Ive talked to are of the opinion the paint will peel and crack, and rightly so, but I'm clinging onto a hope/dream that it can still be done. This machine is going to have a touch of class in contrast with the matt black of the of the more industrial machines I knocked up in the other threads.
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I reckon a roadgoing chopper springer front end wouldn't be too much harder than this little one, everything would just be bigger and thicker. Might give it a go and invest in tools to do it rather than just buyin one off the shelf.

Timbo
Rock on !

SimonJ18
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Post by SimonJ18 » Sun Dec 10, 2006 9:17 pm

That's awesome Timbo, i was beginning to wonder how it was turning out for ya, nice job as always!! early next year i am gonna have a go at building one myself... i have recently gathered some really nice wheels and a couple of frames to hack up etc.. You have really inspired me... great job mate :mrgreen:

Timbo
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Post by Timbo » Mon Dec 11, 2006 3:13 pm

Make damn sure those progress pics you take are posted here Simon ! :) I'm looking foreward to seeing them 8)

Timbo
Rock on !

Blackjack
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Post by Blackjack » Wed Jan 24, 2007 11:33 am

Timbo wrote:This front end was alot more work than I expected, but here it is all tacked and bolted together.

.............................

I reckon a roadgoing chopper springer front end wouldn't be too much harder than this little one, everything would just be bigger and thicker. Might give it a go and invest in tools to do it rather than just buyin one off the shelf.

Timbo

Hmmm...

While well you're investing in the tools you might want to buy a tin opener for that can of worms....

What material you going to use?

You going to weld the rear legs into the lower yoke? Ask anyone who has been around choppers since the seventies where aftermarket springers break. If they don't know, they weren't around 'em enough.

What about trail changes from the rocker geometry?

How you going to mount the brake stay?

I could go on.

There's about the same amount of work in a set of girders, but a lot less rocket science.

Timbo
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Post by Timbo » Wed Jan 24, 2007 9:26 pm

Blackjack wrote: Hmmm...

While well you're investing in the tools you might want to buy a tin opener for that can of worms....

What material you going to use?

You going to weld the rear legs into the lower yoke? Ask anyone who has been around choppers since the seventies where aftermarket springers break. If they don't know, they weren't around 'em enough.

What about trail changes from the rocker geometry?

How you going to mount the brake stay?

I could go on.

There's about the same amount of work in a set of girders, but a lot less rocket science.
Thanks for the reality check Blackjack, but hopefully I have it under control.
I was just going to use DOM tubing with some solid slugs snugly fitted internally, extending around 100 to 150mm beyond the bottom of the trees for the strength factor.

Yes, I was going to weld the legs in. I've seen a few examples on machines which seemed OK. Could you possibly fill us in on your experiences you mentioned above that may better prepare me for what's to come or what to expect ?

I've made around half a dozen of these human powered choppers now, all which comply or follow the rules of the game when it comes to the trail. I've posted a couple of other threads here on this forum whereby the wheel offset is different on each example to compensate for the different rakes and wheel sizes. I suspect though you mean the trail changes as the wheel travels up & down with the road conditions. My thoughts here are pretty basic, but it was to keep the geometry of the rocker arm horizontal @ rest, so to minimise the difference it creates when operated either way.
Does that make sense to you? I didn't do well in English @ school but the pure & applied HSC mathematics wasn't a problem, so it's clear in my head. I'd need a pen and paper to really get my explanation across properly, but feel free to harass me if you suspect I have it wrong.

The brake stay, this is something I don't think I'll be adventurous with, I'll just mount it as similarly as I can to the springers my friends ride, If I have to buy some hardware to complete the job I will.

If you wouldn't mind 'going on', I'd be more than happy to listen, sounds like you've got some experience(s) under your belt, might save me time in testing & rework when I finally get going.

Timbo
Rock on !

Prof
Founder, Choppers Australia
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don't worry

Post by Prof » Wed Jan 24, 2007 10:01 pm

Don't be too worried about the English Timbo. I could never understand Maths even though I had to do it right through school despite wanting to be an art teacher!!! Ended up teaching Tech Drawing! Flunked the maths in my matriculation year... in fact didn't even attend maths calsses for last term. But I managed to pick up enough of the basics as needed for specific problems.

Black Jack... Interested in your comment about springers causing a problem with changing trail, as I believe I have observed that trail changes less on a springer than on teles... and yes I have read that a girder's links can be set up to minimise trail change... But it does appear that a girder would tend to have more unsprung weight that a springer.

However on the other hand chopper riders are usually not cornering and speed demons.

Having ridden a number of springer front ended bikes I'll opt for a properly set up "semi springer" on my shovel as soon as I have some time to build it. By semi springer, I mean springer rear legs and rockers but shockers mounted direct to rockers... best of all worlds to me. Means less unsprung weight and I can still pack my sleeping bag etc under my headlight on trips.

Look forward to your comments.
Chopit'nrideit... Prof

Timbo
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Post by Timbo » Thu Jan 25, 2007 4:43 pm

Having ridden a number of springer front ended bikes I'll opt for a properly set up "semi springer" on my shovel as soon as I have some time to build it.
Hey Andrew, when you say 'build it' do you mean build a new whole bike with a new semi springer front end, or building a new front end for your existing mean machine ?
If it's the new front end only option are you going to fabricate it all, buy it complete, buy components and assemble, or a mix of both ?
Rock on !

Prof
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Post by Prof » Thu Jan 25, 2007 6:37 pm

Just building the front end. Plans so far...

Rear legs of heavy walled tube... friend is building a trike with assistance from a recognised engineer so I'll ask him to recommend material and size for them. Would prefer square section but see what he says...

Triple trees will be 3/4" steel plate with steering post welded in

Legs will attach to top tree with a bolt down into top of tube.

Legs will be welded to outer edge of bottom tree... so welding isn't all the way around to create a potential weak spot.

Rockers of steel plate. You can get mag wheel nuts with the same thread as seat belt bolts. Combined with (I think its teflon) bushes they make excellent rocker pivots.

Will use failrly slim shockers and need to do a bit of a play around with rocker length for best results and to get about 3" axle travel.

Hope that gives a you some food for thought.
Chopit'nrideit... Prof

Timbo
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Post by Timbo » Thu Jan 25, 2007 7:07 pm

Excellent, dont forget to post the progress shots, ( if you want to of course )
I'll look foreward to seeing them, I'm looking foreward to Blackjack's next post and I'm looking foreward to getting this front end in the thread back from the electroplater and powdercoater. Till then it must be beer time :)
Rock on !

Violent_Jay
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SickWork

Post by Violent_Jay » Fri Jan 26, 2007 2:47 am

Omg Timbo..Man when you do things you dont do em by halves thats for sure .. Ive never seen anything like that .. keep up the good work.Love checking back on this site now an then, you've inspired me to build a chop/Pushie too, nothin like your scale though thats mad.
Cheers
Jay

Blackjack
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Post by Blackjack » Wed Jan 31, 2007 5:24 am

Hi guys,

First off the rear legs, I've had some doubts about welding them for a few decades now. Bottom line is that if your day job is welding springer rear legs into the lower tree then fine. If it isn't then you're opening a whole can of worms that can be left firmly closed by clamping the rear leg in the lower tree.

Seen quite a few broken springers (and some of them just broke in normal riding) and that is always where they break, right where the leg is welded to the tree. There's a whole load of things you can do to reduce the problem, true enough. But two things to think about, clamp the legs and you don't reduce the risk of a problem, you remove it, is the first one. Second one is that when some pratt in a car pulls out in front of you and you poke the forks into their door, which would you rather be doing? Dropping the rear legs out of a clamp and replacing them, or making a whole new lower tree as well as the legs?

You're going into production then fine, weld them. You're screwing around in your shed making a set, clamp 'em. Sugar Bear, who probably makes the best springers in the world, welds his. But then he's been doing it for decades and frankly it stops the idiot customers from screwing up the carefully worked out geometry. :D Bear's got a completely different set of considerations from a home builder though.

Geometry, because the bottom rocker is usually fairly short then it describes an arc with quite a tight radius. This means that as it goes up and down there's a fair bit of fore and aft invloved. When it's coming up to the horizontal the spindle is moving forwards, trail is shortening, when it's moving upwards away from the vertical, trail is getting longer. That's one thing.

The other thing is that you don't have this problem with the rear leg. To keep the spring rate something like constant, in an ideal world a line through the pivot on the rear leg and through the pivot on the spring or front leg would be at 90 degrees to the rear leg in the middle of the travel. This minimises the nasty rocking motion in the spring leg and helps keep the spring rate something like linear.

But, the line from the rear leg pivot to the spindle really wants to be horizontal at rest with the suspension loaded, or running slightly up hill from the rear leg to the spindle to keep the trail changes sensible.

So, the chances of all three holes in the rocker being in line are pretty remote, and the ideal position for them is going to vary with the rake of the rear leg.

Brake mounting, well that's easy.

http://www.thefont.pwp.blueyonder.co.uk ... _brake.htm

Well easy to say.....

Briefly touching on girders, yeah the unsprung weight can be higher. But to counter that you don't have a lot of problem mounting coil over dampers on them. Even better girders are as stiff as buggery if their done half right, don't need weird brake set ups, and are relatively easy to build so that you get fairly consistent trail out of a set.

I guess the bottom line here is that you chaps already have the goverment on your case, so the last thing you really want is a rash of snapped off home built springers. If you see where I'm coming from?

You see quite a few "How-To Build your own Springer Forks" posts on the Net. But I've yet to see one that started off "This is how I built the springers I've had on my bike for the last 10,000 miles (16,000 kms)..." it always seems to be "This is how I built the springers on my bike/trike that I haven't finished yet...". Which is a bit interesting......

Prof
Founder, Choppers Australia
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Post by Prof » Wed Jan 31, 2007 10:16 am

Blackjack, your point about clamping rear legs to bottom tree is a good one and I will definitely consider that option.

We definitely don't want home built bikes coming apart or crashing from bad geometry through lack of knowledge hence this website and forums, so your comments are worth all chopper builders taking to heart.

I try to ask a lot of questions of people who have expertise before I embark on "new creations" as well as looking around at what has stood the test of time. I usually manage to over engineer, but at least feel safe that way and am not jepadising other chopper builders chances.
Chopit'nrideit... Prof

Blackjack
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Post by Blackjack » Wed Jan 31, 2007 11:50 am

Andrew,

This probably isn't the place for it, but there's a phrase that sort of sums it up, "best practice".

For a guy messing about in the shed, best practice won't be the same thing as it will for a commercial operation.

For the guy in the shed, best practice is the way of doing it that has the least chance of going pear shaped and dumping his bum in the road.

Seems entirely sensible to me. 8)

Timbo
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Post by Timbo » Sat Feb 03, 2007 12:05 am

Thanks for the informative post and link Blackjack. They great and will prove helpful.
Rock on !

Timbo
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Post by Timbo » Wed Feb 14, 2007 2:33 pm

The bike is finished, and that front end works like a charm !!

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I bent the bars with one of those lever action benders, I was stuck with it's given radius, but it worked out OK, any sharper and the tube would have squashed.
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Sharpy about to go for a cruise !!
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My last two years work in one snap.
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Rock on !

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