Author Topic: Oil Spray Bar Failure M32  (Read 335 times)

0 Members and 1 Guest are viewing this topic.

Offline Hamwic

  • Full Member
  • **
  • Join Date: Feb 2020
  • Posts: 67
  • Location: Hampshire, UK
Oil Spray Bar Failure M32
« on: 10 Oct 2021 at 15:34 »
Hi All,

In the last episode, the oil sight glass suddenly filled with oil whilst riding the bike. There was then a slight "clonk" from the bowels of the engine, but it passed quickly and I gingerly rode home.

Upon stripping the engine, I found that the oil spray bar had fractured at the thread near the pump, broken off after rubbing on the upper timing wheel teeth, and had escaped inside the crank chamber, to be mangled by the crank. All the bits have been retrieved, and a quantity of brass filings washed out of the works. There was plenty of oil in the two chambers, and no other damage seems to have been done.

This pipe was sheared off when I first stripped the machine, so it has "previous" for doing this. As this pipe is basically a resonant cantilever pole when only mounted at one end, is there a way of improving the design to obviate another failure? There doesn't seem to be a register on the far side of the crankcase for the bar to locate in, so would perhaps a steel tube be better than a brass one?

Any thoughts?

Cheers for now
Doug


Offline eddie

  • Master Member
  • ****
  • Join Date: Mar 2006
  • Posts: 1726
  • Location: Hampshire, UK
Re: Oil Spray Bar Failure M32
« Reply #1 on: 10 Oct 2021 at 16:30 »
Doug,
          Your question ' would a steel pipe be better?' - I am surprised that your pipe was brass - Mr Douglas was not known for being extravagant with his selection of materials - I'm sure steel would have been his first choice! I am assuming the oil pump is mounted on the inside of the timing cover, with the spray bar going through a hole in the timing side crankcase. If the spraybar is not a reasonably neat fit in the crankcase, maybe a sleeve could be soldered in place to give the bar some support - thus reducing the stress where the thread ends.

  Hope this helps,
                          Regards,
                                       Eddie.

Offline Hamwic

  • Full Member
  • **
  • Join Date: Feb 2020
  • Posts: 67
  • Location: Hampshire, UK
Re: Oil Spray Bar Failure M32
« Reply #2 on: 10 Oct 2021 at 19:05 »
Thanks Eddie, mine has been repaired in the past, so not sure what should be there. Thick walled steel tube in that kind of size doesn't seem to be popular at the moment, and I doubt I could drill a solid rod that length with any accuracy at the far end. I suspect a high-pressure tubing might suffice if I can find an appropriate size.
 
Before it failed it was a 1/4" OD tube, threaded 1/4 Whit and set with a lock nut, but at 1/8" bore that doesn't leave much meat - about 30 thou wall thickness under the thread, and at least the brass pipe didn't do a lot of damage when it went into the mangle.

I think some local wall thickness increase with an internal sleeve and perhaps some kind of spring-loaded extension at the far end to contact the far crankcase wall might be called for. It'll keep me quiet for a bit!

Cheers for now
Doug

Offline eddie

  • Master Member
  • ****
  • Join Date: Mar 2006
  • Posts: 1726
  • Location: Hampshire, UK
Re: Oil Spray Bar Failure M32
« Reply #3 on: 10 Oct 2021 at 19:42 »
Doug,
          Thick wall steel tube - have you thought of contacting a diesel injection specialist? - they may be able to help out with some diesel injector pipe - that is very thick wall, but may be a bit small in the bore.

  Regards,
               Eddie.

Offline Hamwic

  • Full Member
  • **
  • Join Date: Feb 2020
  • Posts: 67
  • Location: Hampshire, UK
Re: Oil Spray Bar Failure M32
« Reply #4 on: 10 Oct 2021 at 20:51 »
Hi Eddie,

I'd not thought of that - certainly worth an ask. It can't be thicker than 5/16 as that's when it touches the timing gear, so not many options.

Cheers for now
Doug

Offline Doug

  • Administrator
  • ****
  • Join Date: Mar 2004
  • Posts: 4338
  • Location: Glen Mills, PA, USA
Re: Oil Spray Bar Failure M32
« Reply #5 on: 11 Oct 2021 at 03:54 »
All the ones I have seen first hand (A31, Aero 600, two Aero 350) were steel.

-Doug