"BLACKJACK" MiniVelo FatBike BUILD. (New owner, new progress soon!)

LukeTheJoker

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Some of you have probably seen the lead up to this build in my RRB BO#9 Joker thread: http://www.ratrodbikes.com/forum/index.php?threads/custom-diamondback-joker.83242

But I am moving it here as an extra build because the Joker build deserves to stand on it's own in the build-off, it is a cool bike! So this bike will be built outside of the build-off, just because I want to build it!

A quick summary to this point:

Came up with the idea to build a MTB style MiniVelo to go with my 120 tooth road racer and the Joker BMX/Cruiser, I am having so much fun with them that I just wanted this one extra to complete the set. If you have seen my other builds you will know I never do anything standard, with that in mind I went to buy some wheels:



They are 90/100/14 tired rear wheels off those 80cc mini trailbikes you see everywhere, they measure out to 21x3.75 in bicycle terms.

Then I went to buy some new bearings for the wheels and also picked up some leaf spring trailer bushings for the fork rockers:



By now I had some idea of what style of bike I was building so I started to mock them up in Paint.net:







As you can see, my thoughts were all over the place, but I really liked that last one, then I remembered why it was standing out to me, a few months back I had read about the Trek Broadsider, and decided one day I would like to build something along those lines:







So then I tried a similar design of my own:



I liked it, but realised I had reached the limits of what a paint program can do, so decided to try out BikeCad:



Very cool, but too small a bike for me to ride...



A better size, but looks out of proportion. (too tall)



Success! Now I could work on the finer details:



There were many, many more mock-ups involved in getting to this point, but I have only shown the pivotal ones here to keep it brief and interesting.

As to the origin of the name here is a Wikipedia link: http://en.wikipedia.org/wiki/Kata_Tjuta

Next update very soon!

Luke.
 

LukeTheJoker

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bump ! don't want to miss this :113:
Thanks 1HP!

First update: Building a mini ladder/dogbones/fork rockers!

Finally started melting metal on this build today, I spent a couple of days working out the best way to do this, as it is very important that they are all the same length and have no twists or they will bind as the fork moves through it's travel, so I decided to build the 4 rockers in one piece as a kind of ladder arrangement, that way I could be sure that they were all the same length and on the same angle as each other.

Started by cutting the 4 centre pieces, bunching them all together and ensuring they were all the same length, then laid them out with the tubes at the ends and with a strip of steel underneath to raise the centre sections to the right height and clamped it all together, then welded away and here is the result:



Then I marked them up for cutting to length to suit the nylon bushings:



After cutting them to length and cleaning up the cuts, I inserted the bushings and then proceeded to slowly sand and file down the tubing to perfectly match the bushings, with a cool down bath at intervals to stop the bushings from melting, and just keep switching which rocker I am working on to allow them to cool thoroughly:



And here they are:





As you can see I still have the welds to clean up, but I want to test run the fork before I spend to much time on looks, no doubt there will be some changes made yet!

Next time I am out working I will be working on the rest of the fork which will look sort of like a Girvin, but with parallel and equal length rockers...

Luke.
 
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LukeTheJoker

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I can't wait to see those wheels under pedal power! Interested in how you will get a freewheel on them or if you have other plans.
I will be going far easier than I did with "BigJim", this will have no jackshaft, it will have a widened BB and I got a spare brake disc to cut down to make a threaded freewheel mount that bolts on to the rear wheel, much simpler set up, but means it will have a wider Q factor than a standard MTB, but I actually prefer that on an offroad bike, more stability... ;)

Luke.
 
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LukeTheJoker

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Ok, need some opinions...

I have been laying out the steel, spring and rockers for the Girvin style springer fork as shown in this drawing I did a few days back:



But laying it all out on my workbench I finally realised just how big the whole contraption will be, it will only be as tall in the spring region as a regular Girvin, but it will be over 11" wide! It has to be that wide to clear the wide hubs on the trailbike wheels, here are pic's with a standard BMX fork for comparison, it is over twice as wide...





You have to imagine the two outside pieces of tubing as long fork legs and the centre piece as a headtube with the spring mounted in front of it, not off to the side as it is in the pics, the actual forks themselves would look ok, but the wide mounts off the forkstem would be hanging out in the middle of nowhere.

Starting to wonder if it is just going to look stupid, and I should be going with a simpler/smoother looking rigid triple tree set up?

There are of course advantages and disadvantages to both set up's, very low on the list is the actual comfort provided by the suspension (I actually prefer to ride completely unsprung bikes) the main reason I wanted to do the spring set up is just because it is cool looking, and I guess so I could show of my fabrication abilities a bit, but if it is just going to be horrible and clunky to look at, it defeats the purpose.

What are your thoughts? Should I continue with the Girvin style springer? Or should I just cut my losses with only a couple of hours wasted on the rockers and switch to a rigid triple tree?

Luke.
 
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Go for the Girvin style I would say they will be one off and if that's the spring your going to use you can set that to be really hard.

How wide is the widest part of the frame ?


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How wide will it be at the head set tube. ??

I'm really liking that


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Are you going to have 2 top tubes like this ?
then have them going down all the way to the drop outs with the loop round ? That would look sweet


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That is the plan! ;) They wont taper in to meet at the seat tube like the Broadsider though, they will be linked with a plate there.

Luke.
That would look really nice. What size tube are you planing to use?
Would look good if you had everything chunky to go with the wheels.


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LukeTheJoker

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38mm down tube, 32mm intermediate tube, 22mm top/loop/chainstay tube, 32mm fork legs.

It is fairly chunky, could be bigger tubing in places, but this is a good compromise between size and weight, there will be some cool braces added that are not shown in the mock-ups, they will toughen up the look.

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38mm down tube, 32mm intermediate tube, 22mm top/loop/chainstay tube, 32mm fork legs.

It is fairly chunky, could be bigger tubing in places, but this is a good compromise between size and weight, there will be some cool braces added that are not shown in the mock-ups, they will toughen up the look.

Luke.
That's going to look the nuts
I'll be watching this build
Are you going to make the fork yolk as we'll ?


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Going to make the fork similar to this if I go rigid:



But much wider of course!

Luke.
They will look really cool
I've been thinking....
I've always wanted to do somthing like this

Maybe you could have something like that on your forks. Just something different



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