My thoughts on a possible mini bike build

#61
Out of curiosity, sparkwizard, do you have pictures of the fork that failed on you? Have you contemplated on any changes that might make a second version successful?
 
#62
Not the one that failed. That was 25 years ago. My son does have a similar bicycle, though. I can snap a picture of that. I'll post it right here in a few minutes. Yes, I have a plan for the current project. IMG_20240613_175926.jpg IMG_20240613_175915.jpg
 
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#63
The one that failed bent both of those curved tubes between the cross bolt and the axle. The wheel went to the right, the rider went to the left.
The tubes were not strong enough. This one is Chinese. I THINK the one that failed was made in Chicago.
If you'd like to see my current mistake, I will get pics soon, but I can describe it if you want. You might like it.
 
#64
I was bending 7/8 OD .083 wall DOM tubing. I could bend it with the short bar, but I needed to bounce and pull on the lever down at hitch-ball level. My back was screaming and I needed more control, so I got the long pipe. I could easily bend the tube with one hand and a glass of tea in the other. I was able to add a degree or two that way, where I was crawling on the ground, digging holes with my boots to add a degree of bend without the long lever.
 
#68
That leading link is such a cool idea; but I’m afraid that would take a major redo to account for the trail in my case. I really like the Monarch idea, too; but I’m, again, afraid that having the downtube welded already has limited my options.

I don’t currently have a fork to say for sure; but I’d bet that I’m right on pace with a 20” bicycle layout.

My original Schwinn plan was to use bronze bushings to sleeve the pivots already welded on the steerer, and the fork’s pivot would slide over the bushing. A 10mm 12.9 bolt would hold the forks in and keep the tube from collapsing.
I believe I figured the fork pivot out at 7/8” OD, and use 1” chromoly for the curved portion of the legs. 3/4” tubing would be used for the straight fork bar.
To tie into the yoke, I was going to buy a set of clevises I found from a roll cage place online.

The yoke (having to support a 5” wide fork spacing) would be cut out of a 3” long piece of 6” od.125 wall dom I bought; and hope like hell I could heat and bend 1/8” steel plate to form the upper and lower reinforcements.

Lofty; but I can’t wrap my head around how to suspend the yoke and keep it straight yet articulate. That 3/8 bolt would be roughly 7” long!
Would the pivot I thought of even hold together? I’m guess I could always have a beefier steerer machined; but at what point am I throwing too much at an unknown?
 
#69
I’m not certain this is allowed; but if it isn’t, I’ll take it down.

I’ve been purchasing my small tubing online, researching the best deals I can. I was in need of some 1-1/4od .250 wall dom to use as reinforcement of the axle to body joints. My welder friend said 1-1/2 on each side should be fine; but this time make the joints tight. I’ll have the tubing quartered and turned down to fit the dissimilar walls snug.
I was afraid of getting a 12” piece of tubing, in case some is lost in the machining process, so I searched for a 16” piece on eBay. With shipping, the prices there fair better than Amazon.
Having no luck searching a 16” piece, I asked a seller if they could could sell me a 16” cut through a 12” BIN auction he had posted. He simply told me, ‘click the buy it now for the 12”, and put down 16” in the notes and we will take care of you.’

Mind you, the cheapskate in me isn’t who is singing praises here; but rather that he was willing to put himself out there to make the deal. I thought I was the only person left on earth that does that sort of thing. Plus, in talking to him, I found out that he has a CNC plasma cutter, and would be able to make the axle hangers when I am ready.
As I am not sure that, beyond this project I may need his services; I ask that you keep this guy in mind if you do. The seller’s name is matsonmetals_1.

Again, if this is against a rule, please let me know. I just purchased the tubing at 5pm as I was leaving work today. If it turns out I have been hoodwinked, I’ll be the first to let everyone know. Just looking to help a good person out.
 
#70
I have been right there with you, and I am somewhere near that point again, now.
I don't mind some fabrication, welding and grinding, and I guess I love the challenge of figuring out how to best accomplish a goal.
However, I am my own test dummy. I also have a 10 year old son who will never be a victim of my miscalculations.
I haven't seen one in a while, but I do remember seeing motorcycles with that Schwinn type fork. You might find a vintage one on Ebay.
I tried a HF tubing roller with 7/8 DOM to make the curved parts for the bicycle I showed above. It would not bend the tube.
If you don't have one yet, you need to get a 110 volt MIG welder.
 
#72
I buy from Speedymetals.com They have a clearance and scrap section sometimes.
The will cut your order for you. Shipping is cheaper for shorter pieces.
Shootyeah! Thank you!

And that HF tubing roller is a joke to me. I tried a lot of stuff just to get it to bend 3/4” EMT straight, and couldn’t.
I’ll admit, a tool is only as good as the mechanic; but mercy me! I’m convinced my last marriage needed less fixed to work out right!

if I get hooked and want to make another bike (scratch sounds killer!), I’ll invest. We have a nice Hobart at work, that apparently at one time got red tagged, that’s available to wield some skills. I’ve made a couple tools that have stood up to abuse. I like the idea of getting proficient at it.
 
#73
Ha! That Vevor seller got back to me.

Ladies and gentlemen, small PSA here:

Check the location of the seller before attempting to bargain with them. I got turned down; but I imagine a seller in China doesn’t see much good in C-canning a bender stand because it happens too be lying around.

As an aside, selling that bender from China for $100 shipped is pretty remarkable these days!

I guess a trip to HF is in order on Saturday. Return the roller, leave with a bench grinder stand.
 
#74
I bought a metal bender from HF with a stand. It is for bending wrought iron and steel bars, but not tubing.
I bought it for the stand, never took the dies and other parts out of the box. At the time, the whole bender with the stand was cheaper than the grinder stand. It is still bolted to the floor in the garage with a big vise on it.
 
#75
I bought a metal bender from HF with a stand. It is for bending wrought iron and steel bars, but not tubing.
I bought it for the stand, never took the dies and other parts out of the box. At the time, the whole bender with the stand was cheaper than the grinder stand. It is still bolted to the floor in the garage with a big vise on it.
I was actually hoping to find one of those on Facebook marketplace to do the same thing. The ONLY one I found is like 120mi away for $75.
 
#76
Guys, I am trying…

Ordered a 48” stick of 1-1/2” iron pipe to use for the stand last Wednesday on my Home Depot app, and it still hasn’t come in. HD is now telling me tomorrow. Ugg!
 
#79
A bit of progress. The pipe arrived for the bender stand; and I was able to contact a machinist that will make the tubing inserts and widen the triple trees to accept the fork tubes I purchased.

A small setback was caught. That 16” piece of tubing I purchased turned out to be 1-1/2” instead of 1-1/4”. I contacted the eBay seller I talked about above, and he is sending out the 1-1/4” priority mail on his dime. Responded immediately. I just don’t find that kind of service anymore, and that’s a shame. I offered to send the 1-1/2” back on my dime; but he insisted I keep it.

So, if things go well, hopefully the stand is welded up and I can begin to bend tubing by Saturday or Sunday.
 
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