Seal Main page (& Block) - updated 21st February 2011
Seal build Menu - new page!
After joining the excellent model engine forum (see links page) John, from the UK put a set of castings up for sale. These were for the Hemingway Seal engine. It is a Westbury design that has 4 cylinders and a capacity of 13.7cc although it is known as a 15cc engine and was first released in 1947!
Not much was achieved during 2009 but 2010 should bring much better progress as the pair of Seals are my main project.
However if you want to see a Seal engine built and running by a group of people the go to the following link. Craftsman's Museum
Latest progress picture 21- 02 -2011
Construction of the block Menu [Note: to help some readers (who have asked where they can buy an item) I have placed links in the write up which are sources on eBay for the relevant item]
Don't get too excited, I have only got the box of castings down from its shelf, tried to find the build article and dust the plans off! The first two days of the year have been spent building the stock storage system. Tomorrow however will mean a start for real and I am really looking forward to it! So bookmark this page if you want to follow the build of the 4 cylinder 15cc seal engine.
The first task I will undertake is to check the main engine casting on my NEW granite surface plate (thanks to Adam and Jemma and Farther Christmas). After which I will machine the base and head. To read the detail use the menu on the top right hand side of this page.
I have put making the camshaft to one side briefly (see camshaft page) so today I cleaned up the base and top of the block by fly cutting them.
I decided that the first reference point would be the 4 side brackets. By using and set of 1, 2,3 blocks and some parallels, I managed to secure the casting to the milling table. Taking very light cuts I only removed sufficient metal to get a clean surface.
Now the base and top are clean I can attach the casting to an angle plate and clean up the end faces. then it will be a case of making up a machining order sheet to guide me whilst I am in the workshop. I will laminate it to protect it from the workshop environment (and especially me!)
Only managed a short visit to the workshop today. So I decided to face off both ends of the casting. And it raised the second question of the build. The first was a timing question as the plan shows 1,2,4,3 as the firing order when a correction was later made in the magazine that the order should read 1,3,4,2. Todays however relates to the cylinder block casting being over the dimensions of the plan.
With the cuts made to the depth of the plans for the facing cuts I have a larger casting by about a 1/4". If I reduce the casting to match the overall dimensions then the casting will not look as it should. the alternative is to take it as far as I can and then add the dimensional difference to the crankshaft, camshaft etc. I have jet to decide what I am going to do.
I also found a dimension of 9/8ths of an inch and it seems that it has been known about for many, many years. One wonders therefore, whether the sellers of the plans are being fair! Plans should be fit for purpose and these WELL KNOWN (so I have now found out) errors should be fixed before the plans are sold. How many more errors are there that I have yet to find? So I have decided that I will record the errors that I find during this build on the Seal front page and when completed, I will write to the plans suppliers.
I decided today to have a go at boring out the 1.125" diameter holes at either end of the block casting. The first job I did was to turn two blanks that would fit tightly into each hole. Taking the opportunity to centre drill both before removing them from the chuck. Now I had a system to reference the centre position of the hole to bore out it was over to the milling machine. It was now that I discovered that the longest boring bar I had was going to be two short to bore both holes at one setting. Important for this particular task.
Well that was easy enough to deal with, I would make a long boring bar. However before I started I though I best check that the travel available on my mill would be sufficient on the Z or down axis. Yes, you guessed it, there was not enough so it was back to the drawing board as they say.
My only alternative (that I could think of) was to do what Edgar T, himself did, and bore the two holes by using the lathe. This requires the casting to be secured to the top slide and then the boring bar is run between centres. The cross slide being traversed to cut the holes.
My next task was to take off the top slide and this was the first time I have done this. In the end it was relatively painless, only releasing the two bolts normally used to allow the topslide to be set over to turn tapers. Once the toolpost was gone I Placed the casting with its two blanks between centres. This allowed me to measure the gap so packing could be arranged, allowing the casting to be clamped to the cross slide.
The next task will be to produce the packing and make up a boring bar with the ability to increase the cutter easily enough to get to the correct diameter.
Today I spent quite a bit of time on working out the co-ordinates for drilling then reaming the holes in the cylinder block for the 8 valves and 4 cylinder liners. It's critical that measurement should take place from a machined surface and I choose the right hand side face when looking at the photo of the cylinder block on the milling table. I had previously set the casting parallel to the X axis by using the two plugs centre drilled previously.
I normally use my electronic edge finder that lights to show contact, and therefore the edge (after allowance for ½ the diameter of the end) of the part being measured. However the overhang on the edge finder would not allow measurement and I do no possess any slip gauges or the like so I made use of the 'wiggler' set I used before buying the electronic edge finder. It was quite nice to revisit an old friend as it were and the edge was fed into the digital readout, after allowance for the ½ diameter.
Because the cylinder block is a substantial casting and the critical nature of making sure the valves, cylinders, camshaft etc. line up, I made several movements to see that the end co-ordinates looked correct. It was during this exercise that I found the co-ordinates wouldn't work in relation to the 4 holes already there for the pistons.
When checking the dimensions against the other recently bought set of castings, I found yet again that my casting was significantly larger. So I decided to center the mill over the nearest cylinder hole to the datum face and confirmed the 'extra' distance. So after recording the measured difference in case it is needed later, I reset the DRO to zero and carried out the checks for the co-ordinates again. This time everything worked out fine and I decided to center drill the 8 valve stem holes. Then it was the turn of a 15/64" drill before reaming with a ¼" reamer.
The remainder of the session was spent adjusting the belts of the milling machine to reduce speed for boring and a start made on the first cylinder bore. However at the beginning of the next session I will make a plug of the correct size to use as a set standard for all four bores. Whilst each cylinder liner can be 'adjusted' to suit I would like to get them as near as possible to the correct size so I can produce the 8 cylinder liners as a batch. After all I should seek to increase my engineering skills, and accuracy is a measure of progress is it not.
Overall a good session with the many checks proving of worth, even if there was not a great deal of swarf made!
I had a great Easter holiday with both my daughter Vicky and son Adam, with their respective partners Justin and Jemma, down for Adam and Jemma' s engagement party. Whilst it is very nice to see them it does take me three or four days to recover after they have left, so workshop time has been nil until today.
I started by trying to work out where I had gotten to with boring the second Seal cylinder block casting. Previous experience had led me to leave a note on the milling machine the last session, saying it was all set up for the next cut. However the reading on the digital readout did not match my setting when double checking everything. I do not know where I went wrong but the 'y' axis setting was incorrect. Looking through my scribbled note book I saw the reading I was on for the Y axis, but no workings on how I got there.
Whilst it was only a few thousandths out, it meant twice the error before getting to a round bore again. I could either go with the mistake for all 4 cylinders or make the first cylinder larger than it should be, but in exactly the right place. Since the error was contained inside the recess needed for the cast iron lining, I decided to alter the 'Y' axis reading to what it should be and accept that the liner would have to be slightly oversize on its outside diameter, to accommodate the error. At least it would be in the right orientation.
The rest of the morning was taken up with completing the 4 bores for the cylinder linings, including the top recess (see photo in gallery above) followed by drilling out the top of the eight valve bores, reaming to finished size. The penultimate task involved using a 3/8" diameter slot drill to make the recess required by the valve guides. Leaving me with the final task of the day, that of milling away the side of the casting alongside the valves. I wanted to get the casting squared at the same setting as the bores for both valves and pistons, although the final finish will be carried out when the casting is held on an angle plate at 90 degrees to its present position.
It will need to be faced properly on the angle plate, after having the inlet and exhaust ports machined, along with various stud holes. However by taking a cleaning cut now, I would have a good face to make sure the casting was set up as true as possible. That was enough for me for the first session back and it is progress at least.
Today I managed to drill, then tap the oil filler holes on both cylinder blocks of the Seal engines. The set up time for any machining task is normally much longer that the metal removal and today's task was a fine example of the little extra effort in making another engine.
The first job was to set the adjustable angle vice up on the milling machine. The plans call for the oil dipstick filler hole to be at an angle of 20 deg to the engine blocks head. The way I set this angle was to use the digital angle meter I have. A much valued tool and a recommended addition to any workshop. It was first zeroed on the milling table then with the casting standing on a pair of parallels, the meter placed on its top and the vice adjusted until the correct reading was seen.
I decided that I would reduce the speed of the drill and use three different sized drills before starting the tap. This method ensured that the threads would be cut in line with the drilling. However I find it easier to move the casting to the bench and finish the thread, BUT only after it has been started in the same position as the drilling.
Well I have been a little apprehensive about the inline boring of one Seal block (the other had been bored out by the previous owner before I bought his set of castings) because its a procedure I have never done before. In addition I would be using my Myford lathe I refurbished earlier in the year and a home designed and made, tool setting device. So all in all, a culmination of previous work.
In the end, like many times before, the reality was not as bad as was thought. the tool setting device worked very well indeed, allowing me to adjust each cut and bringing in the bore to 1/2 a thou. Not only that but both bores were the same as well. So the Myford behaved herself and the boring bar worked fine.
I started off firstly by working out how much packing I needed to bring the casting up from the cross slide. I did this by using my new (to me) slip gauges. I have been searching for an imperial set at an affordable price for months and eBay came to the rescue. The one lesson in using them was to have a digital caliper at hand to check whether the slip was end on or sideways.......but they worked a dream.
Another lesson was to mount the bar so there was sufficient travel for the casting. needless to say I put it the wrong way the first time! I then used the leadscrew to drive the cross slide for each end cut. To advance the tool, the tool setting fixture was clamped on the bar and over the tool piece. Making sure it was facing the right way (yes, I got that wrong too for the first cut) the grub screw was released and the micrometer moved to the required cut.
For the last few cuts the bar had to be removed so I could use the inside micrometer to get an accurate measurement. All too soon it was all over and I was really pleased with the results.
The only item left on the cylinder block is to bore out the two camshaft holes on one block. After that it is on to making the cylinder liners and valve guides. The facing off to size of both blocks can only be done after the cylinder liners and valve guides have been fitted then both flycut to final dimension.
Pleased to get out into the workshop and carry on with the Seal build. Today I spent my time boring out the previously made valve guide blanks. Once this was completed I reamed all the guides 3/32" to match the valves and decided to press all the guides and cylinder liners into place. Before pressing them home using the Myford face plate and tailstock, I checked the depth of recess and the amount of clearance on the cylinder liner or valve guide. Then I measured how proud they were so ensuring they were pressed fully home.
The next task will be to face the block off to size (allowing 5 thou for the base to be cleaned up) so I spent my last time setting the block on mill ready for tomorrow. I did a test running the new power feed and am wondering whether the control of speed has a wide enough range...... Will see the next time....
Today I managed to get the surface fly cut back and also the base but have left 3 thou for final lapping of the top and bottom. Hope its enough! The home made power feed worked great and certainly helped me with the physical side of turning x axis. So that was some good news!
Fitted the valves and couldn't resist trying a couple of springs just to see...don't know why we do it...get ahead of ourselves...anyway I will now sort out a cutter to cut the valve seats.
Decided to test out my idea for cutting the HT steel in half bought for the two crankshafts. My method is to tap the end of the bar (within the allowance of the finished length of the cranks) and secure two pieces of flat bar to it. These are then clamped to the saw table. This will allow both to be secured and remain there once the cut has been made.
Decided to try and make the two from one bar of HT (its very expensive in the UK) bit have left it for the next session when I will be fitter (don't want pieces flying around he workshop!
If it works all right I will start to make the crankshafts next.
