Easy Detents for Shift Rails

This was a fun build. The instructions are a bit sparse for me. Brian Muramatsu's eight year old videos make it easy! https://www.youtube.com/watch?v=UABvEoZ_kuI&ab

The shift rods slide on their own from the neutral position. Original documents recommend that detents can be added with ball bearings, springs, and tapped screws. I created this way of adding detents without the additional hardware purchases, using the magnets that hold down the covers. The magnets set to oppose each other acts as a spring.

By the way, WHERE ARE THOSE COVER MAGNETS SUPPOSED TO BE INSTALLED??? I wish thingiverse had a comment search feature. If you know, please leave a comment!

I solved the magnet issue for holding the covers. Use the parts with "MAGNET" in the name.

PARTS NEEDED:
This uses the same 4mmX2mm disc magnets for the covers. You need 15 of them. 12 might work if that is all you have. Installation is easier if you have a 20+.

PRINTING
The detent pins are three in one STL. They are tiny. They're spaced out to increase time per layer, allowing the previously deposited plastic to freeze before the next layer comes up. I printed them in PLA with a 0.25mm nozzle, 0.05mm height, no brim, with all speeds reduced to 10mm/s. You can try a 0.4mm nozzle if that is all you have - you may need to scale and reprint. Just go slow and avoid stringing and goopy filaments. Use brim if they don't stick - but they're difficult to remove on such small pieces.

Print other pieces as you did for the original transmission housings.

SHIFT RAIL DETENTS
This involves disassembling and reassembling the transmission a few times. You probably got good at this when shimming the shafts with 3mm washers so that gears line up and don't slide axially. It also helps to shim for more neutral space between reverse and 5th gears. The provided diagrams show the minimum number of washers.

Start with the shift rails adjusted to perfect neutral.

Set the top shift rail to dead perfect neutral and mark the rail with a sharpie on both sides of Transmission housing 2. Remove the rail. Repeat this for the middle and bottom rails.

Use a file or small grinding stone to make a divot exactly between the marks on all three shift rails. A "V" shape is better then a "U" shape.

I made my divots larger and on one side instead of shallow all the way around. Clean the rails with isopropyl alcohol to remove the sharpie marks.

ASSEMBLY
This is a precision fit with small parts. Printers, filaments, and tolerances vary. You might need to scale and reprint the detent pins. They're small and they print fast.

Use a 3mm allen key with a swivel ball at the end to ream out the hole where the detent pin pokes through. Push it all the way into the shift rail hole. Clean out the hole of any stray filament.

Install a detent pin in each hole and tamp them down with the allen key. Test them in each hole by holding them down with a 3mm allen key and depressing them in the shift rail hole with the tiny allen key used for the grub screws. Reprint them scaled down if they stick. Remove a stuck one with a piece of insulated copper wire through the shift pin hole.

Install the three shift rails. Test them by putting pressure on the detent pin with a 3mm allen key. Use a sharpie to mark the top of the rail with the divot facing the detent pin. Leave them in while you install the magnets.

Review the diagram for the magnet and keeper orientation. Put 20+ magnets in a stack. Insert three into each hole, sliding the stack off to let three drop in. Using multiple magnets prevents them from flipping over in the hole.

Flip the magnet stack around so that it repels the already installed magnets. Starting from the bottom (reverse/5th) add two to each hole, cleaving them off with the keeper. Fully inserting the keeper will cause the lower magnets to engage the divot in the keeper. Slap the hood. That isn't going anywhere. If you need to remove the keeper, use some magnets to repel the magnets out of the divot.

You now have shift rail detents!

Be careful not to shear off the detent pins when reinstalling the shift rails. Use the tiny allen wrench for the grub screws to push the detent pin down while inserting the shift rail.