Mounting an MTB fender on a Wren inverted fork

Having recently retired, I have been thinking about things I want to do. I've been a bike geek for my entire life, and always wanted to try some long trips including off-road camping, etc., but never had time. Now I have time! I'm starting to have joint pain and other problems that will probably get worse over time, so I decided it's now or never.

I got a great deal on a new Priority 600X hard-tail "adventure" bike. It's an awesome machine that has a Gates belt drive instead of a chain, a Pinion 12 speed gearbox mounted at the bottom bracket, a Wren inverted suspension fork with 110 mm of travel, and Tektro Orion 4 piston hydraulic disc brakes.

When the 600X arrived I didn't have room for two bikes, so I sold my Priority Continuum Onyx. I was sad to see it go- it was a great bike! 

I'll make a thorough post about the 600X soon. 

I will be riding the 600X on Milwaukee's pot-holed streets as well as doing some off-road riding, so I wanted to fit it with fenders (aka mudguards) for wet weather riding. I did a lot of online shopping and review surfing and found the most promising ones to be made by MuckyNutz in the UK. I found a dealer on ebay and ordered a set. 

The rear fender fits on the bike just fine. The front fender was a little bit of a problem. MTB front fenders are made to attach to the fork lowers and bridge. The Wren fork is inverted - the lowers slide into the stanchions instead of sliding over them- so it doesn't have a bridge. There wasn't enough room to mount the fender on the lowers, so it has to go on the stanchions and the fender can't move with the wheel as the fork compresses. I tried mounting the fender on the stanchions but it wasn't stable enough- it really needs a bridge to stabilize it. 

The Wren "inverted" fork. The "lowers" slide into the stanchions and there is no bridge.

Typical MTB fork. The "lowers" have a bridge connecting them together and they slide over the stanchions. The bridge is a convenient place to mount a fender, light, etc. 

Almost every problem, both personal and scientific, can be solved with a 3D printer, including this one. I spent a few minutes measuring the fork and the fender and designed a 3D printable bridge. It fits the stanchions tightly without requiring any additional clamps. I printed it with TPU and tried it out. Perfect!

The fender attached to the fork stanchions with velcro tape. It was very wobbly.  The slots in the top of the fender are for using velcro tape to stabilize the fender on this fork's nonexistent bridge.

The fender mounted with the 3D printed bridge. Very stable! The fender can be installed and removed in just a couple minutes without tools.

The 3D printed bridge. I used black TPU filament. It fits the stanchions tightly and stays put without any additional clamps or tape.

The fender is mounted on the stanchions that do not move with the wheel when the fork compresses. That means it has to be mounted pretty far above the wheel so the wheel won't hit it when the fork compresses, or for street riding, mount it close to the wheel and lock out the suspension. There's plenty of room along the stanchions for either use.

If you have a Wren fork and want to add fenders, you can download the STL file for the bridge here.

Fun for Cats!

 Arrakis 2.0 has been my coffee table for well over a year. I probably turn it on a couple times a week to just change the pattern currently on the table, or to draw new patterns. When the 1000 mm/sec spiral erase pattern runs, Ms. Kitty recognizes the sound that the table makes and comes running to chase the ball. She will push anything on the table to the floor so it won't be in her way. 

I'm hoping to catch that on video one day and will post a link here if I do. There's another thing I want to catch on video. Sometimes she spins around so fast that she loses her footing (maybe she gets dizzy?) and falls off the table. If I catch that on video, Ms. Kitty and I will be making the late night talk-show tour and probably die rich and famous.

Anyway, I was thinking about cat toys and which ones keep Ms. Kitty interested and which ones she gets bored with. I've come to the conclusion that cat toys that will hold the her interest for a long time should have random motion at speeds that she can keep up with or a little faster. The toys Ms. Kitty never seems to tire of are balls hanging by string on the end of a stick and a laser pointer. Both exhibit movement that will catch a cat's attention and move as fast as you move your arm. Everything else bores her to tears.

That got me thinking that she might find it interesting if I make the ball on the sand table move in random directions at random speeds. To that end I wrote a spreadsheet that would generate the necessary gcode. The spreadsheet generates gcode that will move the ball a random amount at a random speed, then stop for a random period before darting away.

The spreadsheet needs to know the size of the table (or the area to which you want to restrict the ball's motion), the minimum and maximum allowable speeds, and minimum and maximum allowable dwell time. It's currently set up to create 500 moves, so if you average 2 seconds of dwell time at each point, you can expect the pattern to run for about 17 minutes. That's long enough for Ms. Kitty to lose interest (she's usually good for just a few minutes), but can be easily extended if she ever demonstrates interest for the duration of the pattern. 

Now I know what you're thinking. "I'd like to try this with my cat and sand table." There's a link to the spreadsheet, below, but before you get too excited, you should know that I run the ball between 500 and 1500 mm/sec with acceleration at 10,000. Ms. Kitty won't pay much attention to anything slower. Arrakis 2.0 achieves that speed by using servomotors instead of steppers. If your table uses stepper motors, it's probably limited to a maximum speed around 100 mm/sec, and that might not draw much interest from your cats.

The servo motors are NEMA17 size, so you might be able to fit them into your sand table, but they also need step/direction/enable signals to run, and a beefy power supply- Arrakis 2.0 uses a 350W 24V supply.

Here's the spreadsheet.

I tried to implement similar random motion using arcs instead of straight lines, but it's a much more complex problem- the arcs can go beyond the limits of the table and that causes the table to stop moving. If I make any progress on it I'll post it.