Hoglet Build

Drawings and build article were in Model Engine Builder issues 10 & 11. You can now by them digitally, go to Subscribe along the top, then subscribe online and it lists all te back issues

JasonB, that's a lovely job!

It should be even better when I get round to finishing it

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Moving on. I made the second cylinder OK.

Over to the mill and used the DRO to drill the holes through the cooling fins.

Made the 8 studs. Threaded them at just one end for now and will get the final length when I have the heads done.

So far it seems to be going to plan.

The drawing does not make any mention of a cylinder head gaskets. .......... I am presuming it will need them.? Suggestions of material and thickness please guys.

Nick

I tend to use a liquid gasket from the likes of Halfords, its basically a silicon type in a toothpaste size tube. You just need a smear of it so don't need to allow for any extra thickness

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Cheers Jason,

The camshaft is an item that I may struggle with as I have never done such a thing. - Think I have the kit to do one and watched a few youtube videos ............. But they are all a bit Greek and voodoo dark art to me.

Nick

You need a Rotary table and boring head with a simple tool holder, set up and cut one face of the cam.

Then keep making plunge cuts as teh table is turned say 2deg at a time

Until you are left with something looking like a cam, just file the tip radius

Then when you have done it for the other cams it should look like this

Simples!

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Cylinder heads next I think.

The drawings give details of a jig to hold the head while the machining of inlet and exhaust ports, spark plug holes and cooling fins take place. The valve guide holes and head securing holes have to be made into the cast iron blank first to enable it to be fixed. - These are then a ref point for everything else.

So this eve I made the jig from a length of 2"x2" square bar as suggested.

I am wondering ............. And thus asking the members here if they think I should machine the ports and spark plug hole first then the cooling fins. Or fins first then the holes.?

Here is a section of the drawing detailing the head.

Also not sure of the best way to secure the valve guides when the time comes.?

I gather that one of the main issues and problem areas with a small 'home made' IC 4 strokes is getting the valves to seal properly with the head.

Thanks, Nick

Nick, if you don't machine the fins before parting off the head I suggest you at least drill and ream for the guides as the 1st op on the parted off piece so you can fix the head to a jig by screwing thro the guide positions.

You may be able to use 1 grub screw at the centre of both guides, the threaded hole would need to extend to each guide and provide evidence of a thread on each.

Emgee

Edited By Emgee on 14/03/2016 22:50:44

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Cheers for the reply.

Yes it's got to be done that way for the jig to be able to hold the heads for the other steps. It's the actual exhaust outlets and inlets through the sides of the head and the spark plug hole I was asking about before or after the fin grooves. I should have been clearer initially.

Thanks, Nick

I did all the drilling first as its going to be very hard to drill across the fins without the drill wanting to wander and some of the holes start in the gap between two fins.

Also check your spark plug spanner will fit the suggested 7/8" hole and adjust if needed.

Aim for a press fit on the guides with a drop of 648 for good measure.

J

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Thanks Jason, that makes logical sense.

The thought of 648 I did consider but was concerned that the cylinder head temp with the engine running may go over the bond point of the locktite.

The NGK CM6 plug specified has a 14mm spanner requirement yes.? - I have just measured the dia of my long reach socket and the external dia is 19.5mm so looks like I will get away with milling it to 20mm (a cutter I already have) and give me a bit more beef on the fins as the hole is quite close to the edge at 7/8th.

Thanks again, Nick

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After making the jig I have made a start upon the cylinder heads.

The 2 blanks were faced off to the required length in the lathe then over to the mill where I used an edge finder to get the best centre of the cast iron stock. The DRO was then used with a spotting drill for marking out the holes.

These holes will be the ref point for fitting to the jig for all the other machining stages to the heads.

The jig was then fitted into a 4 jaw and dialed in true. The head blank was then fitted to the jig for machining the sides to a 2 1/2 in dia.

Then to check they fitted.!

The jig and the blanks will be made friendly again upon the mill for the several hole drilling sessions of the inlet / exhaust and spark plug threaded hole. All hopefully at the correct angles.

I must also remember to make one head a left sided one and the other a right as they are not interchangeable. This being due to the inlet and exhaust port holes being of different sizes.

Nick

Edited By Nick_G on 16/03/2016 22:50:16

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On with drilling and milling the heads. Used the jig once again for the angles required.

Milled a recess for the spotting dill.

Then drilled out with a 9 mm drill as the spark plug thread is 10x1 mm

Then milled down to accept the spark plug body and giving enough room to also accept the spark plug spanner.

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Question.?

The bottom of the electrode. (the 'earthy' one) is about 140 thou shy of the face of the cylinder head. This seems as if its sitting a bit high to me.! Should I make it lower by increasing the depth of the pocket above so that it's about flush with the cylinder head face.?

Easy to do now as the jig is still set up at the correct angle and centered in the mill. But not so easy if I have to go back and do it later.

Nick

Hi Nik

My choice would be to leave the electrode just shy of the head surface. If too recessed the compression ratio will be effected.

I guess the .140" may be the difference between the start of cut in the head and the point where the full diameter was being cut with the slot drill, if so the designer perhaps used a different measuring method.

Emgee

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Hi and thanks very much for the reply.

The depth that the spark plug sits is down to the depth of the recess created in this step with the counter bore operation. :-

Cheers and thanks again, Nick

I just pulled the heads off mine and my plug sits a bit further down, this is just finger tight so will probably leave about 1mm of female thread showing on the shallow side when tightened up

Edited By JasonB on 17/03/2016 18:12:42

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Thanks once again Jason.

That hoglet of yours will be back into all it;s component pieces before long.  

I am going to cut the fins in the heads a little bit different than the drawing. - Just to make this engine 'mine' 

Valves.! ............ I am as yet undecided if to make them as one piece as per the drawing or make them as the stem and then the valve its self and then silver solder them together.?

Nick

Edited By Nick_G on 17/03/2016 19:08:54

I usually make mine from solid stainless, the only time I have used the two part method is on large valves where turning down 3.25" of 7/8" stainless to 3/16" seemed a waste of material and using a separate stem was more accurate than trying to turn it.

If you allow for the stem to be say 3/16" longer than needed a VERY small ctr hole can be put in the end to support it while the rest is turned. Part off, face the head to thickness and then using either a split bush or if you can poke it up from the back of a collet the ctr hole can be turned away.

Not a Hog but same method

Before parting off the length of bar makes a good handle to lap in the head

J

hi nick, your making a lovely job, what did you use to cut the seats ?