Author Topic: A Robinson from rejects.  (Read 71969 times)

Offline Jasonb

  • Full Member
  • *****
  • Posts: 9466
  • Surrey, UK
Re: A Robinson from rejects.
« Reply #210 on: February 16, 2018, 03:51:00 PM »
Thank you Sir, looking forward to it.

Progress may be slowed a little as it's the time of year to think about repotting my Bonsai and I did not do many last year so plenty to do this time around.

Offline RayW

  • Full Member
  • ****
  • Posts: 735
Re: A Robinson from rejects.
« Reply #211 on: February 16, 2018, 07:51:24 PM »
Thanks Graham and Jason for the o-ring advice. I had assumed that the rings needed to seat on the bottom of the groove to ensure that the outside of the ring was held in contact with the cylinder wall. I have now made new cast iron rings and installed them on the piston relatively easily by locating one end of the ring into the groove, then gradually feeding the rest of the ring into the groove in a sort of spiral action until just the second end is left to slip down and into the groove.

One ring is a nice snug fit widthways in its groove, but the other is a bit too narrow, but I am wondering if this will matter as there is really strong compression and suction anyway. The piston is quite a tight fit in the cylinder at the minute, although it does move up and down with a bit of a push. I am not sure whether to leave it as it is and let it bed in with plenty of oil when running, or whether to hone the cylinder a bit more to give slightly freer movement, but at the risk of losing a bit of compression when fully bedded in.
Ray

Offline Alyn Foundry

  • Full Member
  • ****
  • Posts: 1653
  • North Wales, Great Britain.
Re: A Robinson from rejects.
« Reply #212 on: February 16, 2018, 08:01:32 PM »
Hi Ray.

An emphatic " leave it alone " from here....

Once that heavy flywheel is fitted and turned a few times things will " bed " !!

Cheers Graham.

Offline RayW

  • Full Member
  • ****
  • Posts: 735
Re: A Robinson from rejects.
« Reply #213 on: February 16, 2018, 08:49:27 PM »
Thanks Graham. That was what I thought. Next job is to machine the flywheel.

Ray

P.S. Yes, I did eventually drill the 1/32" gas hole. The problem why I kept breaking so many drill bits was that a tiny piece of the hard tip of the first bit that broke must have been left in the hole. Consequently, the other bits broke when they hit it. I eventually drilled a 3mm hole through from the other side then made a brass jet for the inside and a steel blanking plug for the outside so that that hole cannot be seen.
Ray

Offline RayW

  • Full Member
  • ****
  • Posts: 735
Re: A Robinson from rejects.
« Reply #214 on: February 17, 2018, 04:03:15 PM »
Completed machining of the flywheel today, apart from cutting the keyway, which will have to be done on the lathe as I do not own any broaches or an arbor press. I followed Graham's advice and opened out the bore with a small boring tool prior to finishing with a reamer. The result is a nice snug fit on the crankshaft and, hopefully, no wobble!

P.S. A handy hint  - don't stick your thumb on a grinding wheel while it is running. I did today while grinding a boring tool and it really hurts. Net result is a groove right through my thumbnail and deep into the end of my thumb.



Ray

Offline Roger B

  • Global Moderator
  • Full Member
  • *****
  • Posts: 6133
  • Switzerland
Re: A Robinson from rejects.
« Reply #215 on: February 17, 2018, 04:50:18 PM »
The engine is looking good  :praise2: The thumb not so good  :(
Best regards

Roger

Online Kim

  • Global Moderator
  • Full Member
  • *****
  • Posts: 7862
  • Portland, Oregon, USA
Re: A Robinson from rejects.
« Reply #216 on: February 17, 2018, 05:18:11 PM »
P.S. A handy hint  - don't stick your thumb on a grinding wheel while it is running. I did today while grinding a boring tool and it really hurts. Net result is a groove right through my thumbnail and deep into the end of my thumb.

Yes!  Excellent hint, Ray! I did that many years ago when I was working my way through school, working in a small machine shop.  Made a deep divot in my thumb nail and my thumb.  Still have a slightly odd shaped thumb nail which I blame on that incident!

Hope your thumb heals quickly!  Ouch!

The engine is looking great too!  I have been following along enjoying your build.
Kim


Offline RayW

  • Full Member
  • ****
  • Posts: 735
Re: A Robinson from rejects.
« Reply #217 on: February 19, 2018, 07:40:37 PM »
After toying with various ideas I got round to sorting out the big end lubricator today. Came up with the solution shown in the photos. Basically, it is an internally threaded tube with a small threaded plunger which, when screwed down, forces the grease through a series of interconnected holes ( as shown on the plans), exiting through a hole in the main journal. With all the holes filled, just a couple of turns on the plunger produces a nice "worm" of grease at the journal.
As can be seen, clearance is pretty tight - maximum length for the greaser body is 10mm.

Ray
Ray

Offline Ian j

  • Full Member
  • ****
  • Posts: 47
Re: A Robinson from rejects.
« Reply #218 on: February 19, 2018, 08:15:33 PM »
Ray,
Great minds think alike!
This is my solution as I didn't fancy drilling the crankshaft after it was assembled. On my fabricated base there  a little more clearance.The oiler/greaser is as yours.

Offline RayW

  • Full Member
  • ****
  • Posts: 735
Re: A Robinson from rejects.
« Reply #219 on: February 19, 2018, 08:55:53 PM »
Snap!! I must admit that I was a bit apprehensive about drilling the crank after it had been made, but it proved quite straightforward. Like you, my initial thought had been to fit the greaser into the big end cap, but as the cap is quite thin already in the centre, I was worried about weakening it too much by drilling and tapping for a 2BA thread.

The main job left to do now is the keyway in the flywheel, a job I am not particularly looking forward to as the only way I have of cutting the keyway is on the lathe, which is not ideal.
Ray

Offline Ian j

  • Full Member
  • ****
  • Posts: 47
Re: A Robinson from rejects.
« Reply #220 on: February 19, 2018, 09:37:11 PM »
"he main job left to do now is the keyway in the flywheel, a job I am not particularly looking forward to as the only way I have of cutting the keyway is on the lathe, which is not ideal. "

I built this slotting attachment:-

http://www.homemodelenginemachinist.com/showthread.php?t=4366&highlight=lathe+slotting+attachment

No plans, just from the photo's. Main part milled from a lump of ali. ( sounds familiar :) ) works very well----I don't cut that many keyways.

Offline RayW

  • Full Member
  • ****
  • Posts: 735
Re: A Robinson from rejects.
« Reply #221 on: February 19, 2018, 10:41:56 PM »
Thanks Ian. Just had a look at that link and how spooky is that - my initials are RSW! Now I feel I ought to have a go at making it.
Ray

Offline Jasonb

  • Full Member
  • *****
  • Posts: 9466
  • Surrey, UK
Re: A Robinson from rejects.
« Reply #222 on: February 20, 2018, 07:34:58 AM »
I never had a problem doing keyways in the lathe by using the carrage before I bought some broaches. CI is quite easy to do, steel takes a bit more effort but can still be done - these four are 3/16" wide and 1" long in steel


Offline Ian j

  • Full Member
  • ****
  • Posts: 47
Re: A Robinson from rejects.
« Reply #223 on: February 20, 2018, 05:05:46 PM »
Today working on the gas plumbing. The needle valves I had looked a bit industrial to mount as yours Graham plus they were female, So I went for a similair method used on the red engine shown in an earlier video ( this was the one I saw running at the Anson museum) Just need to set the timing and see what happens !!

PS Tried the hot tube burner and that's OK. In your video Graham is that in real time from lighting the burner and getting the engine to run ie just a few minutes to get the ignition tube hot enough?
« Last Edit: February 20, 2018, 05:11:32 PM by Ian j »

Offline RayW

  • Full Member
  • ****
  • Posts: 735
Re: A Robinson from rejects.
« Reply #224 on: February 20, 2018, 06:48:12 PM »
Looking very good Ian. We will expect the video of the first run any day soon.

Ray
Ray

 

SimplePortal 2.3.5 © 2008-2012, SimplePortal