Depending on the printing material and the quality of the print, we have found that the sun gear can become stripped from the axle of the wheelchair. We have created a solution for this involving a 5/8 inch sized ratchet socket.

Dremel the socket to the approximate height of the sun gear (24 mm), and drill two holes in the side (9mm up from the bottom of the sun gear).

Insert the adapted socket into the hole in the sun gear (File is called, Sun_Gear_With_Holes_For_Axle)

Use two Number 6 screws to secure the socket to sun gear.

Procede with assembling the Hand Drive as usual.

Geared up version of Hand Drive

Assembly Instructions

Print out the parts

(1) Annular gear

(1) Bar Holder

(1) Base

(1) Knarp tensioner

(3) Planet Gear

(1) Ratchet

(1) Stacked Gear

(1) Sun Gear

Hammer in three 5/16 inch bearings into underside of the sun gear.

Attach three planet gears to stacked gear using three M3 30mm screws and three M3 lock nuts.

*Make sure not to tighten lock nuts too tight, as the planets must be able to spin freely.

*30mm screws are too long and the ends need to be dremeled off so the surface is flat (other lengths of screws can be used accordingly.)

Take one M3 20 mm and put it through the ratchet. Sandwich the spring in between the ratchet and the M3 lock nut on top.

Put one M3 30 mm screw through the base, to reciprocate spring and one M3 lock nut, screwed tight to the base.

Sandwich other side of the spring between the first lock nut and lock nut on the M3 screw.

Once the ratchet is loosely attached to the spring, use one M4 40 mm screw to attach the ratchet to the base. Use one M4 lock nut to secure it.

*Make sure the screw is not to tight, so the ratchet can swing freely.

Put one M3 30 mm bolt through stacked gear 8 bearing. Secure with one M8 lock nut on the other side of the base.

*The bolt sticks out of the base. It either needs to be dremeled off flat to the lock nut, or use a shorter screw.

Put the sun gear in the planetary gears so it meshes.

Put the annular gear spider inset into the stacked gear so the gears are meshed.
Slip ten 5/16 inch bearings in the annular gear/spider through hole

*The stacked gear has spaces to accommodate the bearings, so put a bearing in, spin the annular gear/spider, then put the next bearing in again, and repeat.

* If the bearings need to be removed it is easiest to do this with a magnet.

Seal off the bearing hole with tape or glue.

Thread the steel cable through the ratchet and attach to the knarp tensioner.

*You may need to drill out knarp tensioner holes depending on the thickness of your cable.

Attach bar holder to back of base with three M5 20 mm bolts and three M5 nuts. (lock nuts are optional)

*Make sure bar is facing up

Test bar in bar holder and put hand drive on chair. Mark the bar on a height that feels comfortable and cut it down to that height.

Put the correct size bar in the bar holder, and mark the two holes for the screw to go through horizontally.

*Mark with either a pencil or a drill bit.

Drill holes through bar for corresponding horizontal screws.

Use two M4 60mm screws to go through the bar and attach it to the bar holder.

Attach break levers and handle grip to the bar.

*Make sure the brake lever isn’t upside down

*Make sure the brake lever is in the right position (lever forward)

Attach brake cable and knarp to tensioner, and tension the cable so when the cable is pulled the ratchet switches engagement.

Hand Drive Geared Up Components

10 3D printed parts

13 5/16 inch ball bearings

5 M3 30mm bolts (planet gear)

6 M3 lock nuts (planet gear)

1 M3 20mm bolt (ratchet spring)

1 M4 40mm bolt

1 M4 lock nut

1 M8 30mm bolt

1 M8 lock nut

2 M4 60mm bolts

3 M5 20mm bolts

3 M5 nuts (lock nuts optional)

1 knarp

1 handle bar grip

1 23mm diameter bar

1 brake cable

1 mountain bike brake lever

1 spring