Roy's Little Engine

[Dave Otto]

Here is a picture of the same S&S sensor mounted on the frame of my buddies Atkinson Differential engine.

Dave

[Jasonb]

Stick the Minimag one into a 6mm slot with some silicon sealant, it will hold it in place, insulate it and is easy enough to remove should the sensor need replacing.

You could also make the ring that carries the sensor from an insulating material like Tufnol, corian, etc for a belt and braces job.

[Manorfarmdenton]

Bill and Dave - that is a good suggestion.  Thanks.
Jason - I hadn't thought of using silicon sealant as an adhesive.  Good idea. 

Julian from Minimag suggested Tufnol too.  I'll have a look on eBay.

[Manorfarmdenton]

Apologies for my seemingly endless list of queries.  Put it down to ignorance!

The latest in the list - exhaust valve timing.  The Redwings are timed so the cam hits the push-rod at 155 degrees after TDC.  Does that sound about right?

Thanks in advance! John.

[Alyn Foundry]

Hi John.

I just spotted your post, things move very fast here!

In the ideal situation the exhaust should commence to open around 25 past the hour be nearly fully open just after half past and fully closed at TDC. The important one is fully closed on the hour. This allows the atmospheric inlet valve most time to operate.

Cheers Graham.

[Manorfarmdenton]

Hi Graham!

Wonderful thing, the internet!

Thanks for the information.  I'll do some experiments in the workshop tomorrow - I trust my setup will meet your parameters.  Once again I have complicated matters by making the cam like one on a Redwing, simply because I'd had experience of them.  We'll see.......

Best regards, John.

[Manorfarmdenton]

Graham,

Its fine.  Assuming TDC is 00.00 mins, I set it so the cam touched the push-rod bearing at around 00.25 mins, the valve was within a gnat's whisker of fully open at 00.30 mins ( the push-rod actually stops moving at about 00.32 mins) and the valve is completely closed again at around 00.55 mins.  A very slightly shorter exhaust stroke than your ideal one. but I reckon it will be ok.

Thanks for the help.
John.

[Alyn Foundry]

Good morning John.

I’ve always used the “ clock “ for visualising, my age probably, but perhaps not so useful in the digital age!

You might like to try retarding the half time gear by one tooth because with the exhaust valve shutting at 5 to a slight pressure will be made. This pressure will have to be first dissipated before a negative can allow the inlet valve to open. This shortens the amount of time available for induction of the fuel/air mixture.

The above would be considered “ ideal “ but somewhere near will work for our case.

Cheers Graham.

[Manorfarmdenton]

Graham,

That's a very good point, which hadn't occurred to me.  I haven positively fixed the small gear to the crankshaft yet, so can adjust that position if necessary.  It would have been simple to make the dwell of the cam a bit longer had I thought about it, but its a bit late for that now.  I wonder whether I can fit a slightly larger bearing to the push-rod, which would have the same effect.  I'll have a look when I go out to the workshop.

All the best,
John.

[Manorfarmdenton]

Update.  I have fiddled with the position of the small gear on the crankshaft before fixing it permanently, and the cam now starts to move the push-rod 'a couple of minutes before 00:30' and the movement of the con-rod into the cylinder after the valve is fully closed again is infinitesimal.  I reckon that'll do?

John.

[Jo]

I felt brave enough this morning to make a little swarf on the RLE. But first milling the valve stem extensions square it was possible to turn the outside of the head round. Only to find holes 

There were no dimensions for the location of the valves so I squared up the head in the vice and targeting the centre of the two bosses and found that a spacing of 16mm came about central. Then followed a bit of confusion looking at the diameter of the valve heads at 9.53mm diameter and thinking double that = 19 but they are only spaced 16. Then the grey fog lifted and I realised that it only needed 9.53mm plus a small gap between the valves So 16mm is ok.

The drawing then says the head mounting bolts are 2BA clear on the pads. It is a good job I checked the other drawing which says the holes go on a specific PCD

I didn't like the look of those holes  But I won't know if they can be over come until I turn it over after lunch 

Jo

[Jasonb]

Good to see you are back upto working with castings. Hopefully the holes won't come on a valve seat or link between passages.

The couple of R&V engines I have been working on have a good method of placing holes where there are bosses, the drawings have "COB" next to the hole dia. This stands for Center on Boss.

[Alyn Foundry]

Don't despair Jo.

They aren't holes as such, notice the shine on the bottom surface, that was trapped gas. Before we got really organised the R.L.E. comprised of " loose " patterns, each part being individually moulded along with others. This method is ok for the odd few castings but if the moulder runs to the " sprue " without
" turbulence " suppression gas can enter with the metal. The R.L.E. was the first kit to get " plated " with very precise running systems.

You could try to remove them by reducing the thickness of the cylinder head a little.

I do have a few spare cylinder head castings left, so if needs be I can get you a replacement.

Cheers Graham.

[Jo]

Thanks Graham, I think this is a keeper 

The mounting holes when you use the measurements on the cylinder do not line up with the bosses  But turning the head over and picking up the holes for the valves and reaming/boring them shows that the valve faces are well clear of those occlusions.

Drilling for the spark plug took a bit of thinking about. First I drew a circle on the underside of the head so I knew where I wanted the sparkplug hole to come out. then brought the line round the side of the head so that I could trace the line up to the sparkplug land. this was then used with the vice inside a vice to provide the correct angle for milling the sparkplug face and pilot drill.  Luckily I had a 9mm slot drill to cut the sparkplug pilot hole with, then it was a case of tapping it with the head still at the correct angle.

turning over the moment of truth yes close enough to where I had planned it to come out 

The port angles were equally challenging, especially as I had left the head thick on the rim. I am not sure how big the ports should be but I managed to get a 5.5mm slot drill down both at an angle that join up the 3/8 26 threads I had tapped and the valve holes, without breaking into the reamed valve guide holes

Last bit for today (one mustn't push our luck  too much has been going wrong of late    ) was a bit of filling with JB weld to get rid of the holes and smooth things out a bit.

Jo

[Alyn Foundry]

Nice one Jo.

Just the valve seats to cut and finished!

I see you opted for the " improved " version of inlet/exhaust layout, it does make for a neater look!

Yes 5.5 mm is more than adequate for the transfer ports, we want a quiet runner not a racehorse!

Cheers Graham.