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For lateral stability there should be as much weight as possible over the axle with 2 wheels. Kind of like a fork lift load triangle. (Similar to a tricycle as the rear axle pivots in the center.)

For lateral stability there should be as much weight as possible over the axle with 2 wheels. Kind of like a fork lift load triangle. (Similar to a tricycle as the rear axle pivots in the center.)

View attachment 266434
That suggests a shorter wheelbase so the seat will be closer to the rear wheels giving more percentage of weight over the two rear tires.

That would also give more braking action to the rear with the extra weight on the rear. I can probably get by with just brakes on the two rear tires.
WC you are creating a monster here! Really diggin' it!
I like the way you were able to lower the fork / axle to crown height and give the All-Terror-Reign Trike a more low slung look. Chad T makes a couple good points about weight placement as well. You made some great progress since I last checked in.

RaT oN~!
I took a look with a short wheelbase, it looks short but the overall length is still 68". The seat tube is in a good spot for a set of apes matching the front set. A person or two could stand on the back and ride easily
21 May 24 short.jpg

Here's my idea for the bottom bracket. I have the guts for a fatbike and just need to make up the bracket itself. I'll need that wide of a crankset to get low gear on the cluster. My previous setup used a standard bb and the chain would rub the tire before getting low gear. Here's what I think will work:

1. Trim the sides of the donor bracket so it's just a round tube.
2. Slice it down the middle.
3. Thread the bearing set onto each bracket half leaving a gap in the middle.
4. Find a piece of tubing that will slide over the bracket snugly to cover the gap with a little overhang on each side.
5. Get the sleeve welded to the bracket while the bearings are still installed.

21 May 24 bb.jpg

From there it will get welded to the supports that somehow attach to the fork.
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I checked out a boat seat like that for a previous build, but the price was way too high. I'll settle for the plastic kitchen chair.

It's on it's way already, along with the third tire.
The new rim is going for truing today! That means a big burger for lunch.
That little video gives a good idea of the fun you'll have on this. Gonna be cool with those big wheels.
My third tire got lost in shipping and was found the next day. The ad pics show 2 different tread patterns, but for 18 bucks shipped I took a gamble. It should be here in a day or so.

I started out today with the BB. I made sure the threads were good before I used that piece of scrap frame. Now it needs to be cut up and I need a sleeve that will slide over the 1 1/2" shell.
23 May 24d.jpg

Then the struts needed shortened and drilled.

23 May 24 c.jpg

Done. I think it'll have a mad max vibe with that springer.

23 May 24 b.jpg

I worked on the layout again. Keeping the head tube angle where I want it and keeping the length to 68" it sits like this.

23 May 24e.jpg

My latest idea is to make up a framework for the rear wheels that would bolt (or weld) them up to the main frame. I would cut off the rear portion of the main frame, but not until I had the rear section worked out and ready. That would minimize the "utter failure and start all over" risk factor.

I tried some bars in the seat tube. It looks like that will work out.

23 May 24g.jpg

Where the seat will go. That's not the chair I'll use but it shows I can use the rear bars as support.

23 May 24f.jpg

The next task is to come up with a framework for the rear tires. I'm also going to integrate a standing platform into it somehow. I've got a lot of cardboard from a new washing machine box to use for a mock up.

23 May 24 a.jpg
Gonna be cool to see this human powered MadMax war chariot come to life

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The front wheel drive idea is history. I was setting it up this morning and realized it was too dangerous for me. I had thought the ride would be about the same as standard adult trike, but the difference is the center of gravity with my legs up and sitting in a laid back position. If the trike started to go over it would be hard to get footing to right it. The turning limitation was also a factor, but the crash factor was the primary reason I'm going with rear wheel drive.
24 May 24 layout.jpg

It still will use 3 wheels, only the third will be on the sidecar rig. It will be welded up as one frame, it won't be bolted on. I did some research awhile back for placement of the third wheel, it doesn't go parellel and in line with the drive wheel, it needs to be slightly forward by a few inches and pointed inward slightly.
24 May 24 sidecar.jpg

I'm still going with a Mad Max type theme, using sheet metal and rivets. Maybe something like a chariot.

I'm getting the drivetrain and brakes set first. It's going back together like the original except the front is lowered now. The disc brake adapter has to be redone. The rear brakes shouldn't be a problem and the gears are good also. I changed to a 32 tooth crankset, the smallest I have. With the weight this thing will have, a 32 tooth chain wheel with a low gear cog of 34 teeth will have me pedaling faster than the wheel. I might even be able to climb some small hills.
24 May 24 bike.jpg
The front brake adapter won't work with this fork setup, so I'll have just the rear wheels with brakes. I tried to reposition the flanges but still no luck for the brake, but I did lower the front a little more by setting the flanges differently. I think it looks beefier.

25 May 4.jpg

25 May 3.jpg

The third tire showed up and is the same tread pattern, it just has some lettering. Np.

25 May 5.jpg

25 May 1.jpg

The kitchen chair showed up also. It was to be the driver's seat with front wheel drive, but now may wind up as the passenger seat.

25 May seat.jpg
I think a width of 32-34 inches should be good. I'm starting with the base first and then going from there. I'll have this made up of 9/16ths tubing like the frame has down the middle. I can get 20' sections of the tubing, then do some bending and cutting. This uses right at 20' of tubing. Once I have it all bent it will get welded at the shop.
I drew up a plan for the layout. The wheel will be mounted inside the framework with a slot for each side of the axle.


26 May 24 b.jpg
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I make another diagram showing the 90 degree bends and I added it all up. 24' is needed.
A 13' piece will do the whole outer edge with 3' for the inside of the wheel well and 8' for the crossmembers.

26 May 24 plan.jpg
I'm looking forward to the ride video with MrsCat riding in your bmx sidehack.

Maybe I'll be the one riding! :rofl:
We had a bike with sidecar when I first moved here back in 2014. But that was just bolted to the bike with no consideration for alignment. The fork bent from the pull to the right, so I put on a BMX fork. There was no way to adjust the extra wheel. I attached my old office chair and it was a luxury sidecar! I did all the pedaling though.


I've almost got it ready to ride, the two wheel part. I hooked up the gears and used a photo to see how to attach the rear disc adapter. I just need to get a chain on it, the alignment looks like it will get low gear easily.

27 May 24 gears.jpg