Author Topic: Dragonfly of despair, crankshaft restoration  (Read 917 times)

0 Members and 1 Guest are viewing this topic.

Offline AndyMorgan

  • Member
  • *
  • Join Date: Aug 2017
  • Posts: 17
  • Location: Carlisle UK
Dragonfly of despair, crankshaft restoration
« on: 28 Mar 2018 at 21:13 »
"Do not despise the snake for having no horns, who is to say one day it may become a dragon"

 In the jumble of parts that will hopefully become a Dragonfly, there were two crankshafts. I decided to dismantle the one that rattled most, it was also slightly mis-aligned but I managed to push out the crank pin centers and found they were full of a hardened dark grey crud.
Pressing out the crank pins followed

The crank pins don't look so bad

and


but the white metal shells are not so good.
Front looks ok but is a rattling fit on the pin

The rear is a tight fit but with signs of galling


Could the good people of this forum offer a lowest cost solution?
What measurements should I have that are within tolerance?
is it possible to replace the white metal with a roller bearing?


Offline eddie

  • Master Member
  • ****
  • Join Date: Mar 2006
  • Posts: 1438
  • Location: Hampshire, UK
Re: Dragonfly of despair, crankshaft restoration
« Reply #1 on: 28 Mar 2018 at 22:17 »
Andy,
         Your crank has already been heavily modified - it should have 3/16" x 1/2" rollers in alloy cages. I have rebuilt quite a few postwar cranks with new crankpins and INA needle roller bearings. Unfortunately, I no longer have any new crankpins, but I will get back to you tomorrow with details of my method of rebuilding.

   Regards,
                 Eddie.

Offline eddie

  • Master Member
  • ****
  • Join Date: Mar 2006
  • Posts: 1438
  • Location: Hampshire, UK
Re: Dragonfly of despair, crankshaft restoration
« Reply #2 on: 29 Mar 2018 at 09:09 »
Andy,
         As promised, attached is the article describing the method I have used to recondition postwar Douglas crankshafts
 Hope it helps with your Dragonfly rebuild.

  Regards,
                Eddie.

Offline AndyMorgan

  • Member
  • *
  • Join Date: Aug 2017
  • Posts: 17
  • Location: Carlisle UK
Re: Dragonfly of despair, crankshaft restoration
« Reply #3 on: 22 Apr 2018 at 22:33 »
This could well be an early prototype as it came from engine number 1007/6. I have another crankshaft and will see how that one goes