Marklin 3015 repair

Marklin 3015 Crocodile was faulty.  Appeared to be seized up on one side.

I found a diagram of the crocodile, also looked on eBay and found spare parts for the gearbox on sale, so had an idea of how the gearbox came apart.

Thought long and hard about it, then started to disassemble the croc.

Took off central cover and the end pieces.

Eventually decided which side was seized up.  This was identified by manually turning the motor until it was stiff, one side’s wheels had no play, other side had some play.

Took croc apart more by loosening 3 of the four hinge screws, front part eventually separated from central body.

 

This had lots of wires going to the reverser, took reverser out and was surprised it was in two pieces.  Also removed light contacts.  Only wire now keeping the items together was the feed from the pickup shoe.  I decided not to unsolder this.

Next step was to remove the connecting rods and pry off the wheels connected to the worm gear shaft.

Wheel was pried off using two small screwdrivers pushed between the wheel and body and slowly pressed on the screwdrivers to pry the wheel up without bending the shaft.

Made up a special screwdriver from a very worn old one by sawing and filing a 2.5mm slot to allow me to remove the axle inserts. This allowed the axle with worm gear to be removed. 

No damage on gear, so proceeded to take out the worm drive shaft.  Removed the C clip and washer, then using a plumbers pliers to push the shaft out backwards. 

Found a sliver of steel in the worm gear, appears to be swarf, might be from when the thread for the axle inserts were cut. (Screwdriver pointing to metal sliver)

  

Then reassemble the worm gear, found it to be smooth again.  Used plumbers pliers to push the worm gear back into the housing, replaced the washer and C clip.  Adjusted worm gear to ensure no friction by pushing the worm gear in a bit more.

Next assembled the worm axle, then pressed on the wheels again.  Had fun trying to get them aligned to get the connecting rods to work.

I have a sneaky suspicion that even though I found some metal in the gear teeth, the problem with the croc may not have been the worm gear after all as the photos I took of the break down show the connecting rod holes on the wheels on one side at an odd angle that caused the wheels to lock.

Now I am not sure if this was the initial fault or was caused by me manipulating the engine during the disassembly.

Anyway, Crocodile tested and working again.

DIY USB Microscope

DIY Microscope assembled from a very old USB camera and even older camera equipment.
I took the rear lens cap and drilled and filed a hole in the centre.
Then I disassembled the USB camera and carefully positioned it in place so that the USB camera was square with the lens when the cap was locked in place.  Then used hot glue to fix it in place.
Lens was mounted to a bellows.

To operate:
Adjust the length of the bellows for magnification.  Adjust the height from the lens to target object for focus.
Set the aperture to get the best amount of depth versus brightness.  Bigger the aperture number, the better the depth of field.

Download the USB Camera software.  In my case it was Microsoft LifeCam as the USB camera was a VX1000.
Only issue I have is that the old USB camera and software has a significant amount of lag, so positioning the object for viewing takes some time.