Now is time for an admission I am so frightened of making a error that I check everything I do in as many ways as possible
So when I started to make the jigs for this project I was worried about errors when spacing the fins on the barrel and the head
so I made a small test piece that when placed on the surface of the slitting saw located in the previous cut so that every time I
changed the settings I had a tool to prove it was OK.
Today was the day I was setting the saw to 21.6mm depth after getting it on the money I slavishly applied my tool and CLUNK.
it refused to go in the slot. Horrified I checked the settings, And I found I had been so intent on getting the .6 correct I had
inadvertently set to 20.6 mm.
Now you may say that ,surely you would have noticed that, yes but probably, only after I had cut about 1/4 of the cut One tends to get a
bit over confident when doing repetitive work
So 15 minutes making the tool, Saved two days making a new head.
The last radial fins have been cut leaving only the fins on the top of the head to be cut at a later date
The top two fins are cut to twice the depth of the others being clear of the ports and clamping force from the cylinder bolts ETC.
A shrink fit experiment, trying to determine the best way to shrink fit the bronze valve cages and the allowance necessary.
Two samples one of bronze (Quality unknown) and the other of 6082 aluminium both 5/8" dia.
The ambient temp 19°c. both pieces measured and true size recorded.
The bronze was placed in the freezer for 24 hrs at -19 °c on removal no change in size was recorded.
The 6082 was placed on a electric hot plate for 15 min's on re measuring it had increased in diameter .005"
It seems to me that .003"interferance may provide a tight fit and ease of fitting .
And after the inlet flange area comes the exhaust.
So far the 357 gram blank has been reduced to 208 gram and more to be removed yet.
I am sure you will be sick of looking at the same piece buy the time the head is finished.
The bronze is due this week, also I found that I have the need for a internal mic." Well I do don't I" so that is due in the post tomorrow.
While I am waiting I have made a seating cutter for the valves, from drill rod , turning the stem down from 1/2 " to 3mm was a bit buttock clenching
but we got er done as they say.
seat cutter looks nice. IT almost looks like you could have drilled it and pressed or interference fit a small shaft into the cutter if you had to. In fact it reminds me of one that I use to use but it was designed where you put a rod in the valve guide, then it spun on that to cut the seat then you removed it then put on the second one for a dual angle cut on the seat. but that was over 35 years ago that I did that.
I know the very thing you are talking about Ken my son probably still has mine including a throat cutter probably last used on the rebuild of his Healy
The material for the Cages/Cam boxes/Cams and valves are now in my possession so it's time to move on.
The first valve cage is ready to fit, final machining to be done after fitting in case there is any distortion.
I will make the other tomorrow each is matched to the head :003" interference.
It seems that the interference I allowed was two large even after testing samples to see the amount of change .
Also it appears that placing a small part into large one, the heat mass immediately raises the temp of the small part before it can be pushed home.
So the two cages ended up being driven unmercifully into place with a big hammer the inlet cage ending up deeper than was intended causing distress to the area in the head where it sits, both cages broached out a sliver of material from the bores in the head. After the event I found no change to the length of the cage, or any evidence of distortion to the head apart from the inlet cage being .5 mm low in it's bore.
Deciding that the head was probably ruined anyway, I reprofiled the area of the head around the low cage with the flexy grinder and a diamond burr then continued to bore out the throat's and lightly cut the valve seat's , Just to prove to myself I had not got it all wrong .
You can see the reprofiled area of the head around the cage nearest to the camera.
Now I have to rethink my method so I do not ruin another head. so it's time out on the valve work for the moment.
Hi Billy G, on the ball as usual, that is my intention to install the cages with minimal interference & 620 Loctite then with suitable rests to allow the stresses to work out, cut the throat -seat and inlet tract.
Because in my design the springs do not act against the cage but on the head ,therefore constantly puling the cage into position I think it is unlikely that the cage will dislodge The lower spring location plate will also be made to act as a retainer around the guide part of the cage, using 620 to keep it in place, as this is a relatively cool area I doubt anything will move.
Thanks for your input Billy ,Always appreciated This is a big adventure for me so keep your fingers crossed.
By the way did you see my post in the Collchester lathes section.???? A blast from the past.
best regards Brian.
No I have not been on holiday, Just slid down a set of marble stairs, hit the wall and bashed my head on the workshop door, The good news is that the wall and door are OK, I ended up a little fussy round the edges, just required a rest untill the head stopped spinning.
This is a drawing of the intended modification to the lower spring plate changing it from a flat washer to a top hat section .
the photograph is of the parts including the valve spring and cam follower.
Now waiting on delivery of the Loctite.
I am intending to make a set of drill bushes to reduce the ports so i can open them a little at a time
Glad to hear that you are OK. I know falls down stairs can be bad. even without hitting a door. (broken bones) Again glad you are ok. The drawing reminds me of some that I have seen on some car engines
The only thing is setting the backlash looks like it could be a pain.
The lash will be set by trimming the end of the valve stem or putting a shim in the cam follower.
Along with cam timing--- ignition timing & keeping the belt centres correct, while not altering the compression ratio or any of the above. I think it will give me enough to keep me occupied for a while.