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Old 01-10-2017, 08:33 PM   #11
deverett
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The model uses glow plug ignition but the glow plug is rather out of scale. What I did was to machine the hex of the plug down by 15 thou. on each face. The round part below the hex was also reduced in diameter. Hopefully the plug will still work. The design has the glow plug screwing straight into the cylinder casing, but here again I'm trying to get closer to full size and have made a plate that will screw onto the ignitor boss. The plug will slip in the central hole and with a bit of luck when screwed tight, I will still have a seal.

The ignitor plate is a piece of steel about 0.036" thick and this was just sawn and filed to shape after the 4 holes were drilled. Ignore the top two holes; I was trying to be clever and put one hole too close to the edge. Don't want to waste too much - these small bits always come in useful.

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The drawings show the glow plug on the half way line but full size it is below, so this is what I have copied and the glow plug is 50 thou below centre. The two lock nuts have since been thinned down to be closer to prototype.

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The boss on the cylinder will need to reshaped somewhat later on.


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Old 01-12-2017, 10:19 PM   #12
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Moving on down we come to the push rod bracket. This required a piece of 5 x 5 mm steel, of which I had none. A raid of the potentially useful bits yielded something that didn't take too much effort to get down to the correct cross section. The easiest way to hold it was in the side of the vice. A spare piece of the steel was used to balance the pressure of the vice jaws while the holes were drilled and the slot machined out. The part then had to be turned 90 degrees for the ignitor push rod hole.

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The ignitor pushrod shown (round bar) is a convenient find from a dead printer.

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Lastly, the part was trimmed to length to give:

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Old 01-13-2017, 09:06 PM   #13
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Dave,

I used to hate setting up small parts in my 6" milling vice until I invested in one of these.

A 1" Vertex toolmakers vice, just set it down onto parallels and use it to hold all the small parts, no more trapped fingers or bodging up some way to support them. I usually use bits of lathe tool steel as parallels for it.



I could even use large cutters around it.

Mine was rather cheap compared to what they cost nowadays, but if anyone needs something like this, Arc Euro sell them and they have a 10% discount offer at this time.

John
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Old 01-13-2017, 10:14 PM   #14
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Another good tip. Thank you, John.

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Old 01-15-2017, 11:38 PM   #15
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Now after that little light relief, it was back to the next real job: the crankshaft brackets.

They have a taper along their length so to hold them in the chuck, the thin end was padded out to get a decent grip. The chuck is a Grip-Tru, so it was quite easy to get reasonable concentricity. Man, that aluminium is gummy; lots of WD40 didn't seem to make any difference.

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With the register machined, the casting was reversed in the chuck and held by it to turn the taper. If I had followed the drawings, the taper should have been 5 degrees. I managed 2-1/2 degrees to keep a decent amount of metal at the front.
The housing was drilled out 9.7mm so that when temporarily fitted to the crankcase I could check the alignment before reaming.
It was pleasing to note that after turning the step in the back that I got a nice light push-in fit with both brackets in the crankcase. So it does pay off to measure twice and cut once after all!

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I did notice that using the small carbide boring bar(dry) that the quality improved considerably while machining the recess.

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Old 01-15-2017, 11:53 PM   #16
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Still watching Dave. It's nice to see a "real" Hubbard going together.---Brian
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Old 01-20-2017, 12:41 PM   #17
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With the brackets ready to fit, the first one was pushed in place. Using the DRO's PCD function, it was easy to set out the 6 holes for the retaining studs. Tapping holes went through both parts and the bracket was eased out and the holes in the crankcase tapped.

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The metal is less than 80 thou thick so my intention was to fit lock nuts in the cavity. That was until the inevitable happened: I had either too much pressure or perhaps not enough pressure on the tap when withdrawing it and the thread stripped. Yes, locknuts are now a definite necessity! That was the first side done. The casting was unclamped and the parallels rotated to give clearance for the bosses on the front of the cylinder. Same procedure as before to line up the casting and repeat drill and tap. Well, darn me if the same thing didn't happen again and another thread came out 'rather loose'. Each housing and the crankcase was centre popped by the top hole: one pop for the front and 2 for the rear, just in case there is any discrepancy.

I now needed some studs to hold the three main bits together. Don't care what the purists might think, but I have some 7BA threaded bar that I'm going to use. Just need a quick way of getting 12 studs to the same 3/8" length easily.

How I did it:
Use any piece suitable of material- in this case a piece of HSS - in the front toolpost as a stop bar + the rear parting tool.
Move carriage towards the headstock so that the parting tool is Just clear of the chuck jaws. Lock saddle.

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Adjust topslide so that the distance between the cutting face of the parting tool and the piece of steel is 3/8".

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Put the threaded rod in the chuck and wind the cross slide in so that the stop bar makes a stop for the embryo stud and nip up the chuck.
Wind the cross slide back out and the parting tool will come into play.
Cut off stud, withdraw parting tool, wind in cross slide cleaning up cut end if necessary and pull out the material from the chuck... And so on. Takes longer to write about it than do it. 12 studs in about 5 minutes. I held the stud material directly in the chuck, but there was no damage to the threads.

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With everything ready for a trial assembly I discovered that there isn't sufficient room within the crankcase to fit locknuts; the holes are too close to the walls - not my mistake I hasten to add!
A peek inside the crankcase will show what I mean with a potential locknut alongside an inserted stud, so a quick decision determined that two-component locknuts (JB Weld) will have to be used instead.

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After having said elsewhere that the castings were undersize, a measurement over the crankcase flats showed that after machining they are 15 thou over! I'm not going to argue with that: I need all the metal there that I can get. I'm sure no-one will notice.

The crank brackets were temporarily bolted in place and I was very pleased with myself when the 10mm drill was pushed through to check alignment, and all did indeed line up.

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The brackets now needed the bushes, so these were turned up from a suitable piece of bronze that was long enough for both parts. Taking note of what Brian discovered about wear in the bushings, I made sure I used bronze instead of ordinary brass.

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The two bushes were pressed into the housings using the vice. A couple of pieces of padding protected the end of the bushing and the face of the housing. I just started the press and then put a drop of Loctite 638 in the housing as a' just in case' but the press fit was quite tight, so whether the Loctite actually did anything is moot.


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Old 01-20-2017, 03:05 PM   #18
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Coming along really nice now Dave, and a good write up as well, I can understand everything you are doing..

John
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Old 01-24-2017, 12:59 PM   #19
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The drawings show a groove in the bushes for oiling the crankshaft. Remembering Brian's wear problems with his crank bushes, I decided to follow full size practice and use proper grease cups. On the full size engine there is one on each housing and they stick up like butterfly antennae. I will put a spiral groove in the bushes stopping short of the ends and hopefully keep the crankshaft well lubricated.

The grease cups were made in 4 parts. I put a hexagon on a suitable piece of brass bar then turned down a bit on each side to form the union, the cup and cap were simple turning jobs and the stems started life as a tent peg!

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The crankshaft brackets were again temporarily fitted and the assembly held in the vice at the appropriate angle. Holes were drilled and tapped for the grease cups.

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Old 01-30-2017, 01:54 PM   #20
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Jumping around a bit, I wanted to make a couple of small parts that form the ignition lock out. Made from 3mm steel bar, the end was threaded 10 BA and then the 12 BA pivot screw hole was drilled and tapped; the bar was turned 90 degrees so the 1mm slot could be made and the piece parted off afterwards.

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The lever was filed up from some 1mm steel.

Completed bracket, lever and pin. A bit closer to the real shape.

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One more little bit to make - the other part of the ignition lock out. P2.7a and P2.7b in the drawing above. This was done in similar fashion to the previous part.

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It is now time to start work on the crankshaft. I was hoping to have some sort of counterbalance but soon realised that if I did, the crank would not go in the hole so I will have to be content with the published design!

After facing up the six faces, the holes for the round bits were drilled and reamed.

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The block was then turned 90 degrees and a rounding over mill was used to get rid of the square corners. While in one piece, I could do top and bottom on the ends but then the original piece had to be cut into two pieces for finishing off.

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The round bits had previously been turned and were press fitted into the webs using the bench vice. As with the crank bushes, I put a drop of Loctite 638 in the holes before fully pressing together. They were cross pinned afterwards; the holes being lightly countersunk to receive the piening over. I used the shanks of old Dremel wire brushes as rivets.

Here's the crank. I took the picture after I had tried it in the bushes. It was a bit tight but I'm sure it will work itself in OK. Probably better to be too tight than too loose!

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