Just finished a leaf spring front fork setup. It's pretty stiff. Let me know what you think.
Here's a pic.
Here's a pic.
Leaf Spring Front Fork
- Thread starter neicull
- Start date
I like the simple concept.
Is trail predetermined or experimental?
Are the rockers bushed? Just some things to think about.
I would want more than one bolt on the base of the spring. Despite the wheel axle and spring pivot bolt to tie it all together, the spring could still theoretically walk to one side under heavy breaking.
JMO,
Dave
KC
Is trail predetermined or experimental?
Are the rockers bushed? Just some things to think about.
I would want more than one bolt on the base of the spring. Despite the wheel axle and spring pivot bolt to tie it all together, the spring could still theoretically walk to one side under heavy breaking.
JMO,
Dave
KC
The simple concept is definitely what I'm going for.
This is pretty experimental, were going to try different spring resistances, right now it's very stiff.
There's a nylon sleeve inside for the through bolt on the spring end. If I can find something better I will consider using it. It's such a small load on the spring that bushings may be over doing it. I'm trying to keep things affordable at the same time.
The single bolt on the base of the spring hasn't seemed to let the spring walk any, but that's a good point. It's using a 1/2 serrated bolt so I'm confident it won't slip. I may come up with a notch mount or weld on a tab that allows for two bolt holes. Good idea. Thanks for the feedback. I want to keep it as simple as possible, ultimately, for the sake of cost and design. I'll do a little more testing. This hasn't been configured for a front break yet.
This is pretty experimental, were going to try different spring resistances, right now it's very stiff.
There's a nylon sleeve inside for the through bolt on the spring end. If I can find something better I will consider using it. It's such a small load on the spring that bushings may be over doing it. I'm trying to keep things affordable at the same time.
The single bolt on the base of the spring hasn't seemed to let the spring walk any, but that's a good point. It's using a 1/2 serrated bolt so I'm confident it won't slip. I may come up with a notch mount or weld on a tab that allows for two bolt holes. Good idea. Thanks for the feedback. I want to keep it as simple as possible, ultimately, for the sake of cost and design. I'll do a little more testing. This hasn't been configured for a front break yet.
As far as the spring rate, you could mount the axle outboard as opposed to inside on the rockers. This will give greater leverage using that stiff spring. This can go only so far as stresses on all parts(especially pivot points) are increased using leverage to overcome a spring that is too stiff. Additionally, you likely have decreased your trail significantly. A spring that settles when mounted will effectively increase the head tube angle and further decrease trail. Big bumps do it more.
I would mount it up and take some measurements for trail. Having rockers extending the axle forward will eat into your trail and you might end up with a bike that is unstable(might even roll backward better than forward). Once you measure it, if it is 2" or less, you could consider turning the fork around then mounting it all back up. This will restore some of the trail. To even begin to do it correctly you have to take the simple trail measurement with the head rake and wheel you plan to use. Experimentation is great but the testing begins with knowing the geometry you have created not just that it "works". Build it, then reverse engineer it to fit safe and proven specs - certainly so if you are selling something.
About the bushings, I meant how are the rockers at the bottom bushed? Without bushings, they will wallow away in no time - especially if you mount the axle outboard to increase the leverage. Either way they must not be just bolt on metal.
Dave
I would mount it up and take some measurements for trail. Having rockers extending the axle forward will eat into your trail and you might end up with a bike that is unstable(might even roll backward better than forward). Once you measure it, if it is 2" or less, you could consider turning the fork around then mounting it all back up. This will restore some of the trail. To even begin to do it correctly you have to take the simple trail measurement with the head rake and wheel you plan to use. Experimentation is great but the testing begins with knowing the geometry you have created not just that it "works". Build it, then reverse engineer it to fit safe and proven specs - certainly so if you are selling something.
About the bushings, I meant how are the rockers at the bottom bushed? Without bushings, they will wallow away in no time - especially if you mount the axle outboard to increase the leverage. Either way they must not be just bolt on metal.
Dave
Thanks for the feedback. I did test ride it, and it worked great. Stiff but it worked nicely. I can do the geometry but ultimately rake and trail is a subjective measurement. I can't afford to engineer a part like Yamaha. I have to use my best judgment. This isn't an unsafe configuration. I have some work left to do with bushings on the rockers. It's still a prototype at this stage. I'll keep you guys posted.
i like it , i saw a nice custom harley with a front like that , i wanted to make something like that myself , nice job .
Good job and good thinking. I love all the talent that is out here. You may need to find a lighter metal for your spring but that is cool. I am going to make a springer for that Whizzer, thanks. Have fun, Dave
lol if you "engineered it like Yamaha" it'd have about a zillion parts to do the same thing, cost a minimum of $800 and you'd not be allowed to fix it else you'd void yer warranty 
However, I have five vintage Yamahas and I have yet to find a design flaw. Gussets are welded correctly, bolt shoulders are the correct length, bushings and spacers are used in the appropriate places, etc. The two cannot be compared. That costs money.
Who can say the same of Chinese products coming into the US? I suspect this is why "all Chinese" cars are not yet here.
But we are on a site where few of the basics are discussed.
JMO
Dave
KC
Who can say the same of Chinese products coming into the US? I suspect this is why "all Chinese" cars are not yet here.
But we are on a site where few of the basics are discussed.
JMO
Dave
KC
A: It was a comparison to the "do it yerself" fork, not the chinese bits.
B: Was a reference to new yamaha, most vintage stuff is an exercise in simplicity.
C: I was joking
Geez, I even like the bdang things lol - Also, I dunno how much more "basic" ya can get then a forum populated by peeps building toys themselves
B: Was a reference to new yamaha, most vintage stuff is an exercise in simplicity.
C: I was joking
Geez, I even like the bdang things lol - Also, I dunno how much more "basic" ya can get then a forum populated by peeps building toys themselves
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Agreed. I just think we need to promote safety. That means doing it right - not that the OP doesn't have the capability to do that. It took me years of building things before I realized there was a reason it took my grandpa all day to fab a part. He was a tool and die maker during the war. I have learned so much since then but it has slowed me down quite a bit. Confidence and capability greatly increases though.
I'll start a new thread and not take away from the OP any more.
I like the concept but can't quite take it seriously until it's "finished". I assume the OP doesn't either.
Dave
KC
I'll start a new thread and not take away from the OP any more.
I like the concept but can't quite take it seriously until it's "finished". I assume the OP doesn't either.
Dave
KC
You finally made something!
Your Fork looks sweetits! I'll buy one if- Is it compatible with a Sturmy Archer Dyno/Brake Hub?
I've been waiting for you guys to make a tank, any news?
Ready to order when you are. and Keep it up!
K
Your Fork looks sweetits! I'll buy one if- Is it compatible with a Sturmy Archer Dyno/Brake Hub?
I've been waiting for you guys to make a tank, any news?
Ready to order when you are. and Keep it up!
K
Still working on the tanks as well as this forks. It'll be 'safe' when it's 'finished'. I agree with promoting safety, due diligence, and US manufacturing. I wanted to get this out there to show folks what's possible and what's coming up. I'd hate for this MAB community the enthusiasm that comes with us to get stail. Like the seat post I'll probably make this compatible with bikes for the most common tube size. I'll make the threaded portion longer as to accommodate most head tube lengths you'll be able to cut it down if it's too long for shorter head tubes.
oh.. and Technocyclist if that bolt breaks. Nothing good will happen. I'm going to put two bolts there that will bolt on a tab that's welded to the fork and gusseted to keep it from walking left and right, making the whole connection much stronger. I would like to be able to provide different rate leaf springs that you can bolt in and out for different suspension qualities.
oh.. and Technocyclist if that bolt breaks. Nothing good will happen. I'm going to put two bolts there that will bolt on a tab that's welded to the fork and gusseted to keep it from walking left and right, making the whole connection much stronger. I would like to be able to provide different rate leaf springs that you can bolt in and out for different suspension qualities.
I built a spring front end for my board tracker using a spring from a utility trailer. the lightest i could find was rated 550 lbs. cut it down rearched it in my hydraulic press. i found the longer you can make it the softer it is. shorter is more stiff. Great job on your prototype.
im looking at the springer forks from piston bikes, $39 any one have any info on these, are they of decent quality , and wonder if i can hook up the hand brakes, im pretty handy but no welder, should be my next investment. thnx chopper
Haha! My dreams are true! I can make my replica of burt munroes bike do they come in 20 or 24 inch sizes? I got a thred posted in strech cruzers and choppers