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Webster IC Engine build log.
Bogstandard:
Nick,
I have used that method a few times in the past, where the valve stems required were rather thin.
As long as your silver soldering is in the capable category, then it saves a lot of wasted material, plus the stems fit the guides perfectly.
John
raynerd:
Hi John
I must admit, I`ve just done one of the valves using the method that Doug described. I didn`t want to do it with the head at the tailstock, ideally I wanted to do it the other way around so I could keep testing the shaft in the valve guide but I think that has something to do with my lacking in confidence in my machining. However, with some careful measuring and using my mircona parting tool with a live centre in the tail stock, it took me about 45 minutes and countless measurements, but I`ve managed one. I then went for a second one, spent another 30 minutes and bent the damn shaft parting it off!! :palm:
I`m in two minds as to carry on and try another. The one I`ve made is a very good fit, but I do believe that it is a fraction narrower than the 3/32 drill rod I have tried in it.
I don`t want to waste too much of your time because I must admit I might go first try and machine another one piece valve but could you briefly explain how you would go about making a 2 piece valve? I think I`ll go tomorrow and see if I can get a few 3/32" drill rod sections and then make some two piece valves and see which are best. I`m guessing you would cut your drill rod section to size and then on the end of a steel bar stock, centre drill, turn the OD and the cut the valve head angle, insert the drill rod and silver solder up? I think I`d have two concerns, holding the shaft absolutely square to the head (will the hole in the head square it automatically?) and secondly, I`d end up getting solder on the shaft and where the shaft and head meet, probably stopping it mating correctly with the valve. Could you loctite the shaft into a head?
Chris
Bogstandard:
I think a little common sense and more thought is required with your last statement.
In such a hot environment, Loctite would definitely not work.
With regards to fitting the seperate valve head. What I do is to make the valve head slightly larger than what is required, drill the hole for the stem then part it off slightly overlength. Just remember, the hole requires to be a couple of thou larger than the stem, to allow the solder to penetrate and make the strong joint required.
That is then silver soldered to the stem, and then a brass or aluminium split collet is made to fit the stem for holding in your chuck, unless you have a very true running collet set. By holding the head as close as possible to the chuck, the head is very finely and gently turned to size, perfectly concentric to the valve stem. When silver soldering, carry out from the opposite side of the head to the stem, just to stop solder flowing up the stem, and on no account, if using silver steel (drill rod) cool it down by artificial means (dropping into water) otherwise you might find that you won't be able to machine the head as it will get hardened too much, let things cool down naturally. I always used stainless steel for the heads.
I have made valves by both methods, and I found that this method caused less anal sphincter twitching when valves with such small stems were required.
Bogs
raynerd:
The plans on page 10 state that the valve guides are "pressed and loctited into place" in the valve block. I was presuming that the valves would therefore be at a very similar temperature as the loctite supporting the guides in the blocks. I`m going to have to get some high temp loctite anyway so I was just thinking it might work for both... clearly your advice is that it will not, but that is where my thoughts had come from.
I`ve just come back from my local K-supplies with a few lengths of 3/32" silver steel however, I expect I`ll try and machine another valve for the time being as I don`t expect my silver soldering skills are good enough. I didn`t appreciate that the hole needed to be a fraction bigger to allow the silver solder to flow into the joint. It seems obvious but my last failed attempt at silver soldering I expect I made the two parts too tightly fitting. I also didn`t consider that the head would be turned after being attached to the shaft. I stupidly was thinking that the head would be turned to shape and size and then soldered concentric with the shaft, which would be extremely difficult. So using the correct method, your basically using the silver steel as a perfect shaft diameter and then silver soldering a wide head blank which you then turn to size once fitted to the shaft so that it is machined concentric with it. Thank you, that makes sense. I may very well give it a go (or even have to give it a go if these one piece valves don`t work out)!
Cheers
Chris
dbvandy:
--- Quote from: craynerd on April 18, 2011, 06:32:42 AM ---The plans on page 10 state that the valve guides are "pressed and loctited into place" in the valve block. I was presuming that the valves would therefore be at a very similar temperature as the loctite supporting the guides in the blocks.
--- End quote ---
The valve guides do not take the beating that the valves will take and the amount of surface area that the valve guides and valve block have will keep it from moving.
My valve blocks never got above 220 degrees F when running full out, so the high temp loctite hold them just fine. The problem I think results from the two piece design is keeping the head and stem concentric without having a perfect collet in my lathe.
I bent one up when I was doing it the first time as well, so don't let that get you down... those things are tiny... I did make a little collet to hold the valve as I faced the head and stem to length. I cut mine off with a hacksaw and then faced it to size.
Doug
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