Author Topic: 15cc Seal and 30cc Seal Major  (Read 11286 times)

Offline Laurentic

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Re: 15cc Seal and 30cc Seal Major
« Reply #75 on: June 22, 2019, 10:30:44 AM »
Morning Jo,     (gosh, you are up and about early for a retired gentlefolk!)

Many thanks for the detailed explanation and picture - all now very clear, clear as the proverbial mountain stream.  :ThumbsUp:

Chris

I'll retire now back into the background to watch the build and leave you to get back to trading banter with Jason!

Offline Jo

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Re: 15cc Seal and 30cc Seal Major
« Reply #76 on: June 22, 2019, 01:13:38 PM »
Pedantry Corner: what you have there are laps. Hones are the things with solid blocks of bonded abrasive material.

Quiet right  :old:  :old:

gosh, you are up and about early for a retired gentlefolk!
.......I'll retire now back into the background to watch the build and leave you to get back to trading banter with Jason!

One has to make the most of one's remaining time: lying around in bed doesn't produce swarf. I am not sure if I would use the term "banter" for Jason's constant criticisms  :hellno:


I hope to get back in the workshop shortly to do the valve guides  :)

Jo
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Offline Laurentic

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Re: 15cc Seal and 30cc Seal Major
« Reply #77 on: June 22, 2019, 02:25:43 PM »
Well, "banter" sounded so much better than "slagging each other off" Jo!!    :LittleDevil:   
But it does make for amusing reading for the rest of us, so please do keep it up!!   :cheers:


Chris

Offline Jo

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Re: 15cc Seal and 30cc Seal Major
« Reply #78 on: June 25, 2019, 12:28:25 PM »
All the valve guide holes have been bored so that the guides are a push fit in their respective holes.

Each hole has been de-swarfed and had Loctite applied before pushing home the guide/liner. These now need to be left for 24 hours before the final finishing cut across the top of the cylinder can be done with the large facing cutter.

In the meantime Mr Silky has been complaining about a lack of attention and is trying to encourage me into doing some studs and he knows how much I like playing with all those nuts I still have to do :facepalm:

Jo
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Offline Stuart

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Re: 15cc Seal and 30cc Seal Major
« Reply #79 on: June 25, 2019, 12:45:32 PM »
Well, "banter" sounded so much better than "slagging each other off" Jo!!    :LittleDevil:   
But it does make for amusing reading for the rest of us, so please do keep it up!!   :cheers:


Chris

They sound like a married couple  :Jester: runs for cover under the duvet
My aim is for a accurate part with a good finish

Offline Jo

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Re: 15cc Seal and 30cc Seal Major
« Reply #80 on: June 26, 2019, 04:59:25 PM »
A quick wizz down the side so that it is square to the crankshaft line:



And a couple of skims off the top:



And the Major block is looking similar to the Seal one:



 :)

Jo
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Offline Johnmcc69

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Re: 15cc Seal and 30cc Seal Major
« Reply #81 on: June 26, 2019, 05:36:35 PM »
 :ThumbsUp:
They look great Jo!

 John

Offline Jo

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Re: 15cc Seal and 30cc Seal Major
« Reply #82 on: June 26, 2019, 05:53:08 PM »
Thanks John  :)

Jo
Usus est optimum magister

Online Vixen

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Re: 15cc Seal and 30cc Seal Major
« Reply #83 on: June 26, 2019, 06:36:06 PM »
"Lord; Lead us not into temptation"

They are looking so good.  :ThumbsUp: :ThumbsUp:

I would love to find the time to build a Seal Major for myself. One day perhaps.

Mike
It is the journey that matters, not the destination

Offline Jo

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Re: 15cc Seal and 30cc Seal Major
« Reply #84 on: June 27, 2019, 10:24:51 AM »
Thanks Mike, one of these days I may come own to visit you and could bring these two down for a visit  ;)


When I acquired my Seal castings from my supplier a bag of little brass mushrooms came with it: These are intended to go on either end of the gudgeon pin as end caps to prevent the gudgeon pin drifting sideways and scoring the liner except, pretty as they are and made to drawing, they are wrong  :( Actually the drawing is wrong and they are correct to the drawing .

Gudgeon pins are easy to make as they are nothing more than a piece of steel turned to length and a hole drilled through the centre. The hole does two things: it lightens the weight of the pin and it provides something to attach those little brass mushrooms with. The drawing mentions hardening the pins but as the pistons are aluminium and the rods ali or bronze I cannot see any need to harden them - if you feel the need then it needs to be done before fitting the end caps.

I am not sure how someone turned those little mushrooms - they strike me as tricky little  :censored: to make. My technique is to turn a piece of suitable sized brass down so that it fits in the hole, drill the all important little hole through the centre of it then part it off over sized. Having turned all 8 in each size they are then stuck into the end of the gudgeon pin for turning.

Now we come to that feature :ShakeHead: in the drawings which means the little bag of mushrooms were made wrong. The 0.8mm dimension is the total height of the brass top not the dimension of the parallel bit, if you make them to drawing the gudgeon pins will be too long to fit in the liner bore  :disappointed: Hence it was necessary to turn that beautifully curved top off on each of them. Personally I use a hand file the curve to match the liner curve rather than using a form tool which is what I think was used to do the originals.

My supplier stressed the importance of getting all of the rotating masses (Piston, gudgeon pin and piston rod) the same so I checked the weight of each of the gudgeon pins and was happy to find that each pin, in each set, weighs the same as the other 3 and that the Seal gudgeon pins weigh exactly 1/2 that of the Major's ones  :thinking:

Piston time  :whoohoo:

Jo
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Offline Laurentic

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Re: 15cc Seal and 30cc Seal Major
« Reply #85 on: June 27, 2019, 01:58:44 PM »
Going back to your lapping method Jo, thinking more about it, I can see it having quite an advantage in that once you have the mandrel and tapered reamer, then all that is to be made is the just a simple turning/drilling/reaming/slitting job on a bit of ali bar.

Up to now I have used Ramon's lapping method (his Lapping Thread from 2013) using a bit of copper plate bent circular and silver soldered to an adjustable rod core; works very well but a bit longer to make, each one is different and needs making entirely, and a bit more expensive maybe in materials.

I mention this as I am making another one now; had I a suitable tapered reamer I might have tried your method!

Nice work on your two orphan engines by the way.

Chris

Offline gadabout

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Re: 15cc Seal and 30cc Seal Major
« Reply #86 on: July 01, 2019, 10:01:56 AM »
Hi Jo, when you bored the block and fitted the liners did you have an interference fit? If so what was it? I have just bored my seal and machined the liners to have at the moment .0015" , will this be too much?
Thanks
Mark

Offline Jo

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Re: 15cc Seal and 30cc Seal Major
« Reply #87 on: July 01, 2019, 12:24:50 PM »
Hi Mark,

The liners were made a light push fit and secured with Loctite which also helps seal the water jacket.

Jo
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Offline Del_61

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Re: 15cc Seal and 30cc Seal Major
« Reply #88 on: July 02, 2019, 02:32:38 PM »
Hi there my first post on this website, so be gentle...!

When I did my apprenticeship last century I was told to allow for an interference fit of 0.001" per inch diameter. So Mark, I suspect that 0.0015 is a bit too much of a tight fit for your liner and bore.

Jo's suggestion seems better, but judging the light push fit is the difficult part, no way would you want to end up pressing in a liner and getting half way and it refuses to go in any further....and then very difficult to remove!

Another idea would be to first pop the liners in the freezer for a few hours before attempting to fit them in the bores.

Regards

Del

Offline Jo

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Re: 15cc Seal and 30cc Seal Major
« Reply #89 on: July 02, 2019, 05:58:08 PM »
Thanks Del, as you are newbie would you like to start a post in the introduction area about yourself and your interest in model engines  :)


Things have been slow doing these pistons  :( To start with I have no castings for the Major and only 3 for the Seal:



These cannot be used as I need 4 pistons of the same weight so all have to be made out of barstock  :Doh:

I have chosen to make the pistons back to back as this makes them easier to hold in the dividing head. Each piston has its outside turned to size and then has the inside turned. I am not sure if the under cut just beyond the gudgeon pin hole is of any benefit but I will do it any way.



The depth was correctly achieved using a slot drill. To get the depth measurement right a 1mm thick rule was used to zero the tailstock dial and then plunged in to provide the depth:



The contours inside can then be turned and the undercut achieved using an internal circlip tool:



Now the pistons can be mounted and have their gudgeon pin holes drilled and reamed:



Having turned then bottom up the centre section needed to be milled out to allow for space for the piston rods. On the first Seal one I got the size wrong as I went by the dimensions on the connecting rod end and only when I looked closely at machined piston did I realise that there was a good chance the piston ring groove will break through  :paranoia:





The set of pistons are coming on:



Before going further I decided it was necessary to see if I can make rings of the required size.

Jo





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