SwingMX from down under - with test ride vid!

[reverendrally]

Lovin Ratrodbikes and all the cool rides on here. After seeing some swingbikes last year and a few youtube vids I resolved to build one of my own so here goes.

I started with two of the cheapest, nastiest, crustiest, BMX frames you've ever seen. They were so bad I couldn't bring myself to take pics of them. This warning sticker off the newer one says it all...

Would you let your child ride this bike?

So a cutting I went. How much fun is it to cut on an old bike. The top tube of the old frame had so much rust and scale in it you wouldn't believe it. Just as well I wasn't using any of that steel. Anyhow, here's my first mockup...

The top tube is an bent VW tie rod off my 60' dunebuggy. It's forged and so nicely bent (by a tow strap on the back of a landcruiser ) that I had to use it. The lower tube is some bright steel tube I had from a previous project. Everything that is going on the bike is recycled like my last custom build, which btw sold for $90 on ebay to a very satified buyer. Here's a pic of it...

The swingbike will be a keeper though.

 

[Graylock]

Re: SwingMX from down under

Just finished my third swing bike. All different style builds, all behave differently. Love them all. I'd like to build one like yours but after another I have in mind.

Here's my latest

GL

 

[reverendrally]

Re: SwingMX from down under

what thing that effects the handling the most? is it the length of the frame or where the seat is or what?

 

[Graylock]

Re: SwingMX from down under

what thing that effects the handling the most? is it the length of the frame or where the seat is or what?

That's the part I'm still working at. My first one was my Huffy that I built from watching a build on youtube. That one is stable from the begining and I use it as a trainer.

The second one is an AZ SideWinder. It's frame pivot is out in front of your knees. It was hard to ride till I changed the angle of the head set and extended the forks.

My Vista swingbike needs, I think, to angle the head set back and a shorter frame. But first I'm going to change the stem so that it will raise the bars and bring the grips back. Still I think it's to long.

One thing I think that effects it is fork trail. This allows the forks to self center. The frame pivot centers everything forward of the pivot. I call it frame trail but that might be wrong calling it that. Putting these two effects together I see the frame pivot at a steeper angle than the head set at the fork. We'll see when I tilt the headset back on the forks.

Then there is your Schwinn style build. I still see frame trail in the rear pivot. Just keep building them till the neighbors complain.

GL

 

[reverendrally]

Re: SwingMX from down under

my thinking is to copy my angles of the original swinn swingbike. I'm interested in your thinking re the angle of the back pivot. angled forward or back and how much?

 

[reverendrally]

Re: SwingMX from down under

Got a few things done today, including changing my thinking re the frame. I've very much tried to copy the original swinn stingray in terms of angles and such. So i ended up with the pivots 700mm apart. I came to this figure based on my size and the need to reach the handle bars comfortably.

I spent about 3 hours just trimming the old bit and hitting them with a flapper disc ready for welding and painting down the track.

Here are the pics...

an initial mockup of angles and such with the bottom bar in position.

both bars in position and tacked in place...

Then welded...

I was thinking about making the bars paralell, but in the end, it looks more organic with the angle. It may get some gussets yet but I'm not sure. I'm pretty happy with the welds too... for once.

 

[Graylock]

Re: SwingMX from down under

Looking good.

GL

 

[reverendrally]

Re: SwingMX from down under

now with gusset...

simple, not too much weld, I'll be using the 3 hole design on other parts of the bike I reckon.

 

[xHOBOPHOBIAx]

Re: SwingMX from down under

I would have made the back tube straight, but that's just me. I'm not sure if it has any mechanical difference.

 

[reverendrally]

Re: SwingMX from down under

I angled the back pivot as such for two reasons;
1. the specific angle gives it a natural castor action that will keep the wheel straight when just riding along without any input from the rider. it also means that pushing down on the pedals with the pivot straight ahead finds the bottom bracket at the lowest point in it's arc, which means it will be less likely to do weird stuff and pivot away under hard pedalling.
2. the original scwinn has a very similar rear angle and they would have put a lot of thought into those sorts of angles for safety (read liability) as well as manouverability.

 

[xHOBOPHOBIAx]

Re: SwingMX from down under

ok, those are good reasons . When I make swing bikes i want them to swing uncontrollably to people who don't know how to ride them :mrgreen: but i guess i'm a little evil.

 

[reverendrally]

Re: SwingMX from down under

you are EVIL! :lol:

 

[reverendrally]

Re: SwingMX from down under

this has been moved to the anything goes build up...

 

[reverendrally]

Re: SwingMX from down under

werl, i miss the build off end...

It's been a year or more since I touched this... amazingly, I didn't throw this project out when we moved recently. although I have to say I was tempted... also, I packaged up the bearings and such and brought everything to the new house in a box and a few things wired together like wheels. So today, I pulled it off my hook board and started. The steel plate was also left over from another project. So I got out my new drop saw off ebay (how awesome is a dropsaw! and $70 too) and set it up. First up I put a hole saw through the plate to shape it the same radius as the crank housing and then cut it in half. Then, I put the two plate together holesawed the same little design into them that is in the frame... only bigger of course...

My little bench drill really struggled with the 55mm holesaw but I got there in the end.

Then for a testfit...

One side will be welded to the inside of the forks to clear the chain. The other side will go on the outside most likely. Still some trimming and filing to do, but it's almost ready to weld together and once that is done I can put it altogether and take it for a test ride!

 

[reverendrally]

Re: SwingMX from down under

well, after some welding... some good, some werl... lets just say the good stuff is hidden
anyhow, the rear carrier is all together and so I put the whole bike together to see what it was like. I lost the chain somewhere, and there is no seat, but you get the general idea.

rear carrier

2 wheel steering...

and it's getting a centering spring and now I totally understand why they had them...
The seat will take some more thinking, not sure what to do with it just yet. The local kids were totally freaked out by it. 8)
One kids said, "that's an idea that could really take off". I let him off the hook and told him someone else had already done it.

 

[reverendrally]

Re: SwingMX from down under

btw, any comments on what sort of seat to get would be welcomed.

 

[reverendrally]

Re: SwingMX from down under

Got heaps done today. Love monday arvos. picked up some more wheel nuts, shortened and installed the new chain, and put it all together. Figured I could ride it without a seat if I sat on the square BMX gooseneck. Let's say it was almost lethal. For a few reasons. First up, without the occy strap you see in the pics the back end literally goes wherever it feels like. Braking makes the back wheel head in whatever direction the foot pushes it backwards. So the first thing I did was put an occy strap on it to hold it in the centre and tried riding it again. This helped a lot. Next up was the seat. The local bike shop that gave me the wheel nuts didn't have an old one so I had to invent my own. I cut off all the useless bit of the BMX gooseneck and welded some thickwall 1" tube I had to it. I then cut it off so the seat could go on top. Not a work of art, but it works very well and still allows access to the gooseneck bolt.

Then I took it outside and rode it A LOT. My neighbour's son was coming home from school at the time and he's been champing at the bit to ride it, so he and I got the hang of it. He's not quite 10yo so he did very well really. See me in the vid below...



A few observations.
1. without some sort of centring spring (in my case the ocky strap) the bike almost uncontrollable. Can't stress this enough.
2. I'm not sure if it's the geometry of my bike, but in most riding the front steering is almost totally unused. Under brakes is a different story.
3. Again, it's my geometry but I've noticed the pedals are very close to the ground and scraped at various times.
4. The other side of the rear carrier needs another diagonal brace and it will get one.

 

[aka_locojoe]

Once you got comfortable riding it did you try removing the occy strap?
I think I've just gotten lucky on the 3 I've built. All are ride-able without any spring or strap.

 

[stretch]

i see the concept in the return spring but i dont exercise it, makes it harder to have fun with it!

 

[reverendrally]

mmm, now that I think about it.... I had no proper seat on the bike and it was the first time I'd ridden it when I saw the need for the spring. Now that I've ridden it some more it might be better. Have to try it again once I fix the front flat (stupid chainstore innertube).