Disassembly

First the snow blower needs to be disassembled: the parts are connected by clips which can be opened by using a screw driver to push them apart. The clips of the drum end disks are not needed later, so I simply cut them off. After the drum has been disassembled the clipped in center part can be removed. 

I hollowed out the housing with my Proxxon Micromot tool and proper cutting and grinding bits, see pictures:

The socket for the chute is replaced by a roller bearing and a printed part and can thus be removed completely. The original center part will be replaced completely and can thus be disposed.

I created all needed parts in CAD with precise fit: blower housing with worm gear box, engine mount, blower fan, gear box cover, distance rings, chute socket with sprocket and cover. I ordered them as Nylon laser sinter printing and already colored accordingly:

Gear Box and Bearings

I used a 6 mm aluminum round rod for the drum shaft. To install the two outer ball bearings to the snow blower housing reduction sleeves are necessary. These are available as printed parts, too. I glued these together with the ball bearings with super glue.

I had to extend the bore of the worm gear to 6 mm, and to make sure that it is absolutely centric I did this on the lathe with an inside cutting bit.

For the gear box I pressed ball bearings 7x3 mm and 12x5 mm into the respective bearing positions. Also the gear box cover gets a ball bearing for the second bearing of the worm shaft. The worm shaft is mounted as shown in the photo. The shaft is 31 mm long. For fixation I used M3x3 worm screws. To position the gears I also used the ball bearings and made sure that the shaft is equally set back in both bearings.

To install the gear box cover M2 threads need to be tapped into the housing. For this pre-drill with a 1,5 mm drill bit with the cover in place. Afterwards the holes on the cover can be enlarged to 2 mm. Now the engine pinion can be put into place. A small bore is in the housing to tighten the worm screw on the motor pinion. Afterwards the worm shaft and finally the worm gear is put into position. Between worm gear and ball bearing a 1,2 mm washer needs to be inserted. 

Don't forget to grease the gears well!

Motor

I used a relatively slow running and high torque brushless motor to drive the blower fan and drum. I designed the printed parts fitting for this specific motor. The green Turnigy motor shown in the pictures is no longer available. The new motor is similar. The shaft needs to be replaced by a longer shaft, which is fortunately possible with brushless motors. To remove the socket set screw I heated the shaft with a soldering iron to soften the thread locker. 

After removing the e-clip I could remove the shaft on the drill press by placing the housing on the machine vise and pressing down with a 3 mm shaft (of course with the drill switched off). I made a groove for the e-clip on the new longer 3 mm stainless steel shaft on the lathe. I also milled flat parts on the shaft for a better bite of the socket set screws for motor and sprocket. Then I screwed the motor to the printed part, and I used the flat head screws which come with the motor to install the blower fan (see photos).
Tipp: If the motor turns into the wrong direction, simply switch 2 of the 3 wires. 

I glued the drum rakes to each other. The left and right rakes can not be mixed up because the connections have either one or two inside teeth. Now the left and right drum have to be adjusted so that they fit exactly without any clearance. For this I carefully adjusted the end parts on the lathe. I fixed the drums with M2 flat head screws to the shaft, the screws going through the shaft. As they cannot be tightened a (removable) thread locker is absolutely necessary.

To attach the end disks I shortened their hubs and glued fitting turned aluminum hubs in place. These hubs are also available as printed parts. The hubs have a M2 socket set screw. To ensure concentricity the turned hubs have to fit tightly and need to be pressed to the disks while glueing them with super glue.

Chute

Following the recommendation of Klaus Bergdolt I enlarged the chute to 25 mm to avoid possible snow block up. For the first version I enlarged the existing chute myself, but for version 2 and the kit the enlarged chute is available as a printed part. To change the throwing distance the black part of the original chute is used.

Chute as printed parts

I carefully enlarged the throw out hole so that it is flush with the chute part of the blower housing. A thin roller bearing with an inner diameter of 25 mm enables the chute rotation. The adjustment is done by RC with a 1:50 motor gear box combination which is installed into the perfectly fitting housing. With the printed cartridge the ball bearing is positioned exactly in the correct position. The cartridge is glued to the chute part of the blower housing and to the inner ring of the ball bearing.

The speed controllers for the chute rotation are really small and they have the advantage that they can be plugged in directly to the receiver. Only wires with a servo plug have to be soldered to them (see picture below).

For version 2 I realized a simple RC adjusting of the throwing distance with a servo which is directly mounted to the chute. I glued the 1 mm steel wire into the groove of the rod of the Bruder chute. Of course this can be made nicer and hidden with a dummy hydraulic cylinder. Maybe I'll do this later.

The chute socket is glued to the outer ring of the ball bearing, and finally the chute is glued to the socket. Now the snow blower is ready for the first test run.

Double Snow Blower

To combine tow blowers to a double blower there are basically two versions:

- two separate single blowers (as I did it for version 1)

- combined blowers with a single center drum, like the original (my version 2)

Separate Single Blowers

This is the easier version. Two identical snow blowers are built, each with end disks on boht sides, which function completely indepent. With the mounting frame they are positioned side by side

Double snow blower with two identical single blowers

Combined Snow Blowers with Single Center Drum

This version is realized at the original, the center drum is one piece. To built this as a model 3 Bruder blowers are needed, because one has to be a part donor.

Due to the self-locking worm drive the drum shaft has to be made of two pieces: the (in driving direction) left motor powers the left outer drum and the entire center drum. The right motor powers only the right outer drum. Therefore the right blower housing has an additional bearing mount as can be seen in the picture below. This housing must be to the right because only then both shafts are hold in position by the end disks and the worm gears and can thus not move. 

To connect the housings I cut the drum mounts like shown in the lower right picture and fixed them with plenty of epoxy glue. The easiest way of filling the 7 mm wide gap is by using the special printed part (see part list at the bottom) which was designed by Constantin Woywod. Alternatively it can be made from parts of the 3rd Bruder blower. I glued both housings together and I additionally used bolts (lower left picture).

Double snow blower with single housing and center shaft

One piece center drum

Mounting to the Snow Cat

To mount it to the snow cat I designed a frame in CAD based on the mounting frame which Westa is using for their double snow blowers. Eric made good photos a couple of years ago when he visited the Westa factory. I removed the bolts at the snow blower housing and drilled 3 mm holes in the exact center (see photo below). I attached the snow blower to the frame with M3 screws. 

The lower screws of the engine mount have to be cut flush to the nut because otherwise they would not fit into the gaps of the mounting frame. 

Finally the cables of the motors had to be extended, for which I used black silicone wires to make them look like hydraulic hoses.

Of course I made the frame fitting to the Pistenking attachment carrier to make the mounting on the snow cat really easy. The multiple wires were bundled with zip ties and guided into the chassis. I'm using a separate battery for the blower motors.

Each snow blower weighs about 375 grams and both can still be easily lifted by the blade servo. The massive snow blower fits size wise quite well to my PistenBully 600 Polar.

To mount a single blower to the Dickie PistenBully 600 I designed a fitting mounting frame as well. It can be simply clipped to the Dickie front attachmend carrier instead of the snow blade.

To mount a single blower to a Bruder tractor conversion kit by ML-Tec a fitting mounting frame is available as well (it was designed by Jonas Dietrich). With this a single blower can be mounted to a ML-Tec front hydraulics Art.-No.: ML-FH-100-01.

Upper right shows a video of the snowblower in operation. 

The measured power consumption for the double snow blower while blowing snow is about 1300 - 1800 mAh for 10 minutes operating time.

List of All Required Parts

All given prices are approximated because prices may always change on short notice.

Printed Parts for a Single Snow Blower:

1x Blower Fan Housing

1x Blower Fan

1x Motor Housing

1x Gear Box Cover 

1x Chute Base + Sprocket 

1x Chute Bearing Base

1x Cover for Chute Gears 

1x Distance Ring for Ball Bearings + Hubs for the Side Discs

1x Chute Top 

1x Chute 25 mm wide for manual adjustment or 1x Chute with servo mount, 25 mm wide

1x Mounting Frame for Dickie PB600 (if the snow blower is installed to a Dickie PistenBully)

or 

1x Mounting Frame for ML-Tec (if the snow blower is installed to a ML-Tec front hydraulics)

Total about € 200,00 plus shipping

Version 1 (left) with 2 separate blowers and version 2 (right) with one piece center drum

At Hobbyking.com:

1x Turnigy TGY-1440A Analog Servo for adjusting the throwing distance (optional), select the fitting chute. Of course any other servo with body dimensions of 20 x 8 mm may be used. The width between the mounting bars is 20 mm. 

Total about € 3,50 plus shipping

At Sol Experts:

1x GM50 Gear Box Motor G50 with metal gears (fits exactly into the mount)

1x ER100 Speed Controller

Total about € 20,00 plus shipping

Additionally:

3 mm stainless steel round rod for the extension of the motor shaft (73 mm long) and for the worm gear shaft (31 mm)

6 mm aluminum round rod for the drum shaft, about 380 mm long
Screws are available for example at www.screwsandmore.de

Needed screws are: 

M3x10 Counter Sunk Screws for the motor housing (5 screws)

M3x5 Hexagon Bolts for mounting the motor (4 screws) 

M1.6 Counter Sunk Screws for mounting the gear box motor for the Chute adjustment (2 screws)

Retaining Washers 2,3 mm for the extended motor shaft (1 piece) 

M3 nuts, washers, spring washers

Mechanical Parts for a Double Snow Blower Consisting of Two Separate Blowers:

Twice the amount of all parts as listed above for a single snow blower, plus additionally:

M3x16 Hexagon Bolts to mount the blowers to the frame (10 screws)

Mechanical Parts for a Double Snow Blower with a one Piece Center Drum:

Twice the amount of all parts as listed above for a single snow blower, except:

5x 295612RC-CAR KUGELLAGER 6X12X4 - Bearings drum shaft, here only 5 bearings are needed. 

plus additionally:

M3x16 Hexagon Bolts to mount the blowers to the frame (10 screws) 

Aluminum Angle 10x10x2, for re-enforcing the mounting frame for the double snow blower with a one piece center drum