Yesterday was a difficult day. I was really pleased with my first valve and took a lot of time over it! Yesterday I ruined it. Ok, it was always going to be a test piece to sort out the machining stages, but I had hoped it would survive after so many chances to ruin it.

Where did I go wrong? Or, where were the problems discovered if I want to be positive. Well the reduction in length to finished size went well to 1/2 a thou (how accurate can we measure with the tools available to model engineers?) and facing the valve to finished depth also was achieved with the little fixture I made. So the process is now set for the production run. So how did it go wrong?

Looking at the plans I have found yet another error! and one that has **&^^%^&* me off. The write up in Edgar's article brought no comfort on his brief description on making the valves and his plan shows the wrong size BA thread! It reads 8BA and the diameter for cutting 8BA according to British fasteners is 0.086" and the plans shows only one diameter of valve stem, 3/32nd" or 0.09367" a difference of nearly 8 thousandths of an inch!

So when I decided to finish the valve by threading the end it was obviously much too large. With previous experience I know the plans are riddled with errors so I thought it must be perhaps 6BA instead. It was over to the books to find out what BA size came nearest 3/32nd". In the publications there are many data tables and drill sizes for tapping threads but little or no data for threading (well not in my books) however a quick search on the internet found the size of 7 BA nearest but the valve stem was 0.00445"  under 7BA. If we go to a thread that is under the stem diameter (and as stated on the plans) then a further 0.00775" need to be removed. This also does not account for a further reduction of between 5 and 10% recommended in some of the literature to stop pushing metal in front of the cut.

Perhaps I should have seen it and checked but I think that the plan should show the reduction in stem diameter, shouldn't it? Another wind up point is the length of the thread is not shown either on the plan or in the article! Measuring against the plan shows it near to 0.250" so that's the plan and I will try the next one with a 1/4" end reduction.

On the positive side I  made a suitable collet for holding the valve in the chuck for facing and bring it to finished size. After the messing about with the first valve I decided to make the final collet in brass for durability.

Well this morning I made a start on the valves for the pair of Edgar T Westbury's Seal engines I am building. Its been a while since my last work on this pair for various reasons but at least I managed to make a start on the valves.

I still have to finish the two flywheels but I seem to have had a bit of a block turning these and instead of ruining the good one I am leaving it alone while I start on something else. The valve stems are very small at only 3/32nd " in diameter (about 2.4mm in dia) and with a little apprehension I made a start by first making a pencil drawing from Edgar T's plans. I find this helps as I at least once have had to focus on the dimensions. Also it helps to clarify my approach to machining order.

I decided it would also be useful to refer to the 1947 Article in Model Engineer for guidance as well as several articles published in Model Engine Builder (American Magazine) but in the end I felt more confused with the different approaches and fixtures shown. So a 'trial' valve was the order of the day  (my excuse in case it goes wrong.....then it turns into a 'trial' piece!).

I started by chucking some 3/8" diameter free cutting stainless steel before facing it off then centre drilling. Once done I decided to run a couple of light cuts to check the tailstock was in line. After the first cut I found it to be out about 2 thou over the short length so adjusted it until it ran true.

I first brought the length of the valve to the outside diameter of the valve over its length (except for approximately 1/4" at the live centre/tailstock end) to the design size of 9/32nd" (just over 7mm in diameter). Then working back from the chuck, using the digital readouts, I came to the point where further reduction of the stem was required.

Because of the thin stem I made light cuts (many many light cuts) but whilst it was more work at least I hoped to reduce the possibility of the valve stem doing its own thing and perhaps wrapping itself round the cutting tool! When getting close to the finish size I again checked it was parallel and was disappointed to find about a thou and a half of an inch difference! However running the tool along a couple of times brought everything back to where it was.

I decided to change the disposable insert for the final cut and was glad I did since it gave a nice bright surface. I then decided to try some of the micro mesh sanding pads I bought for my pens finishes and was really pleased with the results! Will definitely use these for metal as well now. They did work better with a little lubrication (WD40 sprayed on).

Woodturning Lathe MICRO MESH Variety Pack 9 pads3x4    £12.95

WOODTURNING MICRO MESH 9 PAD VARIETY PACK SMALL    £8.95

The next task was to cut the 45 degree face and to do this I set my top slide over to 45 deg. I used the DRO again to scribe a finish line on the outside of the untouched bar and when repositioning the cross slide to the face end simply kept cutting until reaching the scribed line. Checking the distance again with the DRO's (and magnifying glasses!).

Because of the small diameter of the stem I used my Proxxon tool with its Dremel quick fit cutting disc to cut the tailstock end but oversized. Once this was done the tool was changed to the parting tool and using the DRO to set the point I parted off the valve with the depth of the head a little oversize.

DREMEL SC690 SPEEDCLIC ACCESSORY SET IN CASE    £15.95

DREMEL S406 SPEEDCLIC STATER KIT    £9.05

Next time I am going to make a fixture that will allow me to cut the 8BA thread on the end of the valve and also to face off the valve head to dimension, so not quite there yet but I must admit to being pleased at the first attempt! No doubt there are many failures to come with the next 17 needed (or even this one!) so I must not smile too much yet!

Anyway here is a picture for your delectation!

Part finished valve alongside its phosphor bronze valve guide.

I decided to turn the mandrel out of  BMS (mild steel) and set the taper by adjusting the top slide over to give the 10 deg inclusive angle. After getting the bar to run true in the 4 jaw chuck, the bar was turned down to just under the 0.25" diameter required to match the end of the crankshafts. The thread I used was 1/4" x 40 tpi (model engineer thread) so I checked the Drills Taps and Dies reference book in the Home Workshop series (no.12) by Tubail Cain where he recommends a 5% to 10% reduction in size to allow for the Die to cut correctly.

Once the mandrel was made a elongated nut was mad to hold the flywheel against the taper. Once the nut was threaded I drilled out around 1" in length away from the nut. It was then back to the 4 jaw chuck to centre the mandrel, and fit the flywheel.

I was pleased and disappointed at the same time when I ran the lathe because the flywheel ran true! Pleased because of the work done and disappointed because of the work done in turning the mandrel! On reflection I decided that it was still the right thing to have done and really confirmed the trueness of the flywheel.

So that completed all the turning machine jobs and whilst this one is scrap I at least now know the best procedures to produce the flywheel. So the next time I will ready to go full steam ahead and get the two flywheels made.

I managed to get out into the workshop a couple of days ago and carried on with the manufacture of the two brass flywheels I am making for the pair of Seal engines. My session started well enough until I misread the dimensions and removed too much metal from the face! I decided however to carry on with making the flywheel so I could iron out any other problems and also make the tool for the flywheel starting cord. The pictures below show the progress and tool profile.

It is a big advantage to grind your own tools and the profile soon ground. I used the plan to get the correct profile. I took the cuts very carefully and got to depth but the next time I shall use the parting tool to remove more material and then turn to the profiled HSS tool. This should make the process even easier.

I will now have to prepare another blank. Fortunately I still have enough material but will have to be careful.

Well today I managed to get back out to the workshop for a couple of hours. Since the cylinder liners have now been made it was time to start on the other cylinder fittings, namely the 16 valve liners (yes I am building 2 engines).

Having looked at the plans several times and referred to Edgar T Westbury's article published in Model Engineer (April 1947!) it seemed to me that since the guide must have the valve bore exactly central and to size, it would be better to use the 4 jaw chuck to make them.

I then considered the machining process to make the valve guides and due to their shape  the best way forward would be to produce phosphor bronze blanks. These would then be inserted into a special collet (yet to be made) which would allow me to produce all the blanks in one go (see photo of the first trial blank).

The blanks could then be inserted into the collet, which would be set to run true in the 4 jaw chuck. Then the very small 3/32^nd” central hole can be drilled and reamed before finally boring the ¼” diameter inset which needs a special HSS tool ground to shape, allowing the bottom radius to be turned.

Whether this is the best way to make the valve guides I am not sure, and if you know a better way then let me know before I start the job in earnest. Edgar’s article is very skimpy on making the valve guides and this worries me in case there is an easier way to proceed.......A second question arises in my mind in relation to Edgar’s design. Again I will have to do further research since I cannot see why he would have produced the guide with such a small diameter bottom end. It is only 5/32” in diameter and the valve stem is 3/32” in diameter. Making it larger would have the benefit of allowing a larger diameter valve stem, although that may have an influence on the inlet and exhaust volumes......

I may have missed a very good reason for his design being so, so I decided to put further work to one side on the valve guides until I know more and push ahead instead with the 2 flywheels.

Valve guide on the Block casting

]]> http://mikes-models.com/blog/index.php/2010/01/seal-15cc-4-cylinder-valve-guides-and-flywheel-under-way/feed/ 1 http://mikes-models.com/blog/index.php/2009/10/inline-boring-seal-15cc-edgar-t-westburys-engine/ http://mikes-models.com/blog/index.php/2009/10/inline-boring-seal-15cc-edgar-t-westburys-engine/#comments Tue, 06 Oct 2009 17:35:40 +0000 Mike Freeman http://mikes-models.com/blog/?p=1913

I have started to in line bore one of the Seal main cylinder block castings and some 6 months later than expected, used my tool setting fixture for the boring bar (the making of which is on mikes-models.com and the plans for the fixture are available from me if you want a copy - no charge!) which I am please to say works well.

I was a little apprehensive that the movement and positioning of the fixture each time could cause an error but each time I mounted it for the next tool advancement, it read the previous setting exactly. I have long hankered after a set of slip gauges and have scanned eBay for many a month and was fortunate enough to get an imperials set there recently. So I brought these into use when sorting out the packing required between the cross slide and the casting base.

You may well laugh but I had to get my digital calipers just to check whether there marked dimension was width, length etc. Putting that to one side I was able to make two stacks up for the casting to sit on whilst I compared the tapered centre in the headstock with the scribed line on the front of the casting. Armed with this information I then sort out material for the casting to bolt to, giving me the least amount of work. I nearly came a cropper though when I was using a piece of aluminium I thought was the same width only to find on checking it was quite a bit out so it was fly cut in the mill and an extra piece of material sought (ended up as some sheet copper I have) before it was bolted down and the position checked.

After that it was just a case of making sure it was in line (used a dti to make sure) and then mounted the boring bar between a live centre in the tailstock and a half centre (only other MT2 I had) in the headstock. The bar is driven by a dog and home made brass pillar bolted to the faceplate. After checking that I had sufficient movement on the cross slide I had to reverse the bar to allow the full travel.

My next error was forgetting to make sure the tool was in the right orientation (it cut, but not cleanly!) and after I got over the disappointment of the quality of cut, I saw my mistake and put the tool the right way around. From then on (I have yet to complete the task....) everything went as I had hoped and the tool advanced by a known amount. I may live to regret this, but I think it should work fine. Fortunately Edgar T Westbury tells us the diameter is not too critical................we shall see..... Some photo's................

Set of Metric Slip Gauges    £50.00

Micrometer 150 175mm Mahr    £80.00

Slip Gauge Block Lathe Micrometer Turning Grooving    £150.00

COLLECTORS J T SLOCOMB USA 0 1 MICROMETER DATED 1918    £5.99

Today I managed to get the practice cam turned enough to satisfy myself that the system will work so a start has been made on the first of the two real camshafts.

I was hoping to make faster progress but I got distracted by the arrival of another set of castings. When inspecting them I was very surprised to see quite a bit of difference between them. My first set always seemed a little out, especially the cylinder block and head (see photo below). Seeing the second set has confirmed that the size difference is not the same with the second set. Also the sump casting is a lot bigger compared to the rest of the first cylinder block and hen comparing the two sump castings you can see just how much difference there is.

I don’t know if there is another supplier of castings for the Seal other than Hemingways, [link]but if they come from the same source there must be another set of patterns! At least I now know the differences between the both sets and what work I have to do to put them right.

There it is. I have done it now. Whilst the last couple of weeks have been a little 'disruptive' with  being a little under the weather, this has been the least productive fortnight for a while. So what would you expect me to do? Yes I have bought another set of Seal castings that were advertised in a recently published model engineering magazine.

I have hankered after a twin installation in the boat my brother is building. I have also said it is nearly as quick to build two as it is for one. So now we shall see! That's when I can get back out to the workshop of course!

Today I managed to get back into the workshop and having received the camshaft fixture plans and the cutting chart from Steve Huck (thanks Steve) I decided to leave the casting I have been working on and return to making the camshaft.

The first job is to make the fixture and after locating the nearest sized steel, it was a case of squaring up the base and two upper blocks. It never ceases to surprise me how much time is spent in setting up compared to actually making swarf! I now I have to concentrate more than most and this must add some time, but it is still catches me out.

So the sum total of my work today is to get the base to size and the two upper blocks cut roughly to size. More work tomorrow will be required before the fixture is completed. I have time on my side however, as the material I was going to use, then harden, will not now be used. Instead I will be trying Steve's recommendation of using silver steel (drill rod in the USA I believe) instead without hardening. Time will tell but Steve has built, and run successfully, several cams in his engines this way.

So I will need to buy some material for the camshaft. Between its arrival and starting to cut the cam lobes, I will go back to the main cylinder block and carry on with boring the crankshaft aperaures.

Steve Huck's fixture plan sent to me along with the cutting chart.

Well I felt well enough to spend some time in the workshop today so I attacked the cylinder block casting for the Seal 15cc petrol engine build. I decided to fly cut the top and bottom of the casting and by using a set of 1,2,3 blocks, managed to take off enough metal to just clean them up.

When checking the height on the new granite surface plate (Christmas present form my son Adam and his fiance, Jemma) I was pleased to see that it measured the same wherever a reading was taken from. The casting has not been finished to size but I now have a reference point and by using an angle plate I will be able to clean up the two ends. Not much, but it is a start! A couple of photo's to show what I mean.