I felt well enough this morning to restart the machining of the Seal Flywheels. Progress to date involved making the first one (which I made an early mistake on, but continued to check out my machining list), followed by the second today (which will be the first! - confused? You would be working with me!) which I am pleased to say went well and all done to a tolerance of +/- 1 thousandth of an inch (0.001").

And before I stopped I made good progress with the 3rd (well the second really - still with me?) by bringing the blank to overall diameter + 50 thou. Then it was centre drilled, before drilling through 0.250". The next stage was to bore out the rear recess and I am about half way there before stopping. I suspect there is only another hour or so left to do (I can't muck it up because I don't have any more 2.5" dia brass bar!) . Once I have bored the rear recess I will cut the taper for securing the flywheel to the crankshaft.

The blank will then be put onto the between centres fixture, so the work on the front of the flywheel can be concluded. One lesson learnt with the first and unsuccessful flywheel, was the benefit to be had by clearing some material before using the specially ground tool steel for creating the chord grove (see photo). I used the parting tool to depth and when changing to the profiled tool it was significantly easier to machine.

Perhaps because of the positive session today, I have changed my project priority list to next start the crankshafts. This will require some fixture work first so I can cut the very expensive HT steel bar in half (along its length), allowing two crankshafts to be produced from the one piece of steel I have.

I am still having problems with the web hosts I use in getting the main website updated. Why do support staff that are supposed to help not understand that you pay them to be experts in server support! Really wind me up!

Anyway here are a few photo's to help you understand the information above.

GLANZE BOXFORD 16MM SQ INDEXABLE PARTING LATHE TOOL    £32.52

F Wunderlich G Frick K Richter MBO WP Sacred Arias    £15.75

4 CD HAYDN DIE SCHÖPFUNG JAHRESZEITEN Schreier ADAM    £31.50

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I had to have a refresher since its so long since I have switched the lathe on! But I did turn a taper in one of the brass flywheels needed for the pair of Seal engines I am SLOWLY building!  However I have seen some brass swarf this morning, well I am sure it is......... I then spent some time, checking, rechecking and checking again all the dimensions of the work done so far. Its surprising to me how you get into a rhythm when machining and how long it takes to get back into a nearly finished part after a long lay off.

Still it was a nice if very short session since I am a Formula 1 fan and the first race of the season is calling a halt to the day. However I have taken the plans and my machining notes with me to refresh myself ready for some serious work next week (with a bit of luck).

I did find another error with the Westbury plans when checking over the dimensions of the flywheel. the length of the taper at the end of the crankshaft. I was checking the taper (since this was the cut I was making in the flywheel) on the plans and the length of the taper is shown as 5/32" of an inch instead of 15/32"! This error is now added to the 2 9/8" (instead of 3 7/8" it should be) as the length of the main casting.

So its good to be out in the workshop even for a short time.

Work done before on the 'practice' flywheel (ok I made a mistake.....)

The 'practice' flywheel and the turning mandrel

I managed to get into the workshop this morning so carried on with the pair of flywheels for the two Seal engines. The need to ensure they do not 'wobble' when running is important so I decided to follow the advice of Edgar T Westbury in his article published during 1947 (!) in the Model Engineer magazine and make a mandrel to run between centres.

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.

Just had  a short session this morning and continued with the flywheel project for the Seal engines being built. However after getting the outside turning round and facing off I was left with 2.6315" diameter (need 2.5" finished size) so was pleased with progress. I don't know what specification the brass is made to but it machines great!

So feeling smug I thought I would rough turn the inside of the cavity (will be the rear of the finished flywheel) and using one of my home made boring bars before reversing the blank and bringing the front to roughly the correct diameter so that finishing cuts could be made all the better when running the lathe at faster speeds than the unbalanced blank would allow. This is when I hit a snag! One that I did not expect or had come across before using the Turner lathe.

The diameter of the cavity when finished, will be 1.75" and when I reversed the jaws, they were too big to go inside the cavity! So my smart thoughts went out the window! I will now have to remove the remaining excess by another method.

I did however resolve a question I had about the small diameter of the valve liners for the Seal. The answer came to me when studying the drawings last night and the reason is the need for the valve spring to sit over the outside of the valve guide. Mystery solved and I will just have to be careful when making them!

When I resume work on the flywheel I will hold the turned part in the 4 jaws as normal. A few photo's below show progress........

On one visit to my local scrap yard I was fortunate enough pick up a large diameter piece of scrapped brass. It had one problem, which I guess is why it was put into some factories scrap skip, a large cut on part of the bar, but fortunately it had enough unaffected to match the 2 ½” diameters needed for the flywheels.

Brass from my local scrap yard

The first task was to decide a machining procedure for the flywheels and after a little thought I decided that I would make a centre mark and scribe a 2 ½” diameter circle in the available space on the brass bar. This mark would be used to centre the brass  in the 4 jaw chuck by using a centre drill in the tailstock, using the pressure from the tail stock to hold the brass in position on the 4 jaw chuck.

Using the tailstock to centre the brass blank in the 4 jaw chuck

I will then face off the blank and turn the outside to a round shape before centre boring the cavity which forms the rear of the flywheel. Once this is done the blank will be removed and then use the 4 jaw chuck to hold onto the inside of the cavity, the front part of the flywheel will be turned and finished to shape. The final diameter however will not be completed until the flywheel is held on a mandrel running between centres as per Westbury’s suggestions, to get the flywheel turned accurate enough to eliminate wobble when used on the engine for real. Well that was/is the plan.

To save me some effort without producing mountains of swarf, I used the new bandsaw to cut away as much as was safe from the scrapped lump.  This blank was then taken to the 4 jaw and I decided it would be safer to reverse the jaws when holding the rough blank. They would be reversed again when the cavity is produced.

The blank was set up as per my machining plan and the first cuts made to the outside and this is where I decided that enough was enough. The next session will see the continuation of the turning of the outside until round before facing and then boring out the rear cavity of the flywheel. Look back and see the progress

Progress so far on turning the first of two flywheels for the Seal engine

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/2010/01/clarke-bandsaw-performing-well-despite-poor-stand/ http://mikes-models.com/blog/index.php/2010/01/clarke-bandsaw-performing-well-despite-poor-stand/#comments Mon, 11 Jan 2010 16:21:57 +0000 Mike Freeman http://mikes-models.com/blog/?p=2094 Continue reading →]]> #followform { padding-top:5px; text-align:left; }

The reason for buying a replacement bandsaw was to increase the capabilities for metal cutting in my home workshop. My 'old' Warco bandsaw was bought 3 or 4 years ago and to a budget. However, with increasing experience comes greater knowledge. My local source of metal is a scrap yard which means I have all sorts of sizes of cast off's from local industries.

One prime example is a 'lump' of brass that has a part saw cut through the better part of one side. Now I have the new Clarke Bandsaw I can at last cut off sections of the brass lump which I will use to make the two flywheels needed for the Seal 15cc 4 cylinder, petrol engines I am making at the moment.

Once this job has been completed I will put the bandsaw into its vertical position, attach the table and attempt to cut the special steel bar bought for the crankshafts. It is tough steel so I have bought a bi-metal bandsaw blade (has HSS teeth) and see how it performs. A job that the old bandsaw could not tackle (not that this one has yet!). Time will tell.