Scott flame licker build

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Bogstandard:
Bernd,

I had already measured up the bosses beforehand as best I could, that was the reason for choosing them. Before mounting up, I tried them on the upstands without any screws, and as there was no rocking at all, I left them as they were.

If I had tried to level them with a file beforehand, I could have been playing about for hours trying to get them into a no rock situation.

I took it as a 'leave well enough alone' situation.

As it turned out, when measured from the new datum base to the top of the bosses, they were all within 0.002", so to me, to get a casting that close at this stage of machining is doing rather well. The more small datums that are cut, those measurements will get even closer.

Jack,

I agree with you about production castings, but here in the UK, the quality is so bad with model engine castings, they are almost not worth bothering with, just shapeless lumps of metal full of dross and blow holes and costing an absolute fortune.

That was the reason I took a chance on the two sets I bought, because they looked a definite improvement on what has been available the last time I was making from castings.

Bogs

Bogstandard:
Now is the time to start to get the datums on the main bedplate sorted.

You will remember from last time, the bedplate was screwed down to the jig plate, but not yet squared up.
Mounted into the vice, as usual, bedded down onto a couple of parallels and the DTI was then brought into play.

I went all over the castings, looking for areas that matched for squareness, and by taking a few mean figures, I gently persuaded the plate to go into a position where, when machined, datum faces would be produced that would make sure that all the holes will be in the correct position.

The front and two side faces were cleaned up, the rear one can be done anytime as that will not be used in any marking up.

Some people will say I am removing too much of the casting features. All I can say is that I prefer to have an engine that is square, accurately made and not having to bodge things to get it running. If needed, the rough finish can be put back on once everything has been machined.

With the three sides cleaned up and totally square to everything else, it is time to get some measuring done.

The plate was blued up, and by using the two central upstands as datums, I found the centre point between them, and because I had the sides square, by using engineers squares, I could then mark up the centre line and an area of the plate to be machined to become the main vertical datum.

You can see here on my sketch and workings out the datum to be produced, and the exact positions vertically to the critical hole positions required.

Now the bedplate can be held accurately, it will be an easy job to get these holes drilled.

Don't worry about the vertical measurements being shown going to the wrong positions, they are in fact the hole centre heights from the datum face.

Back onto the mill again, and getting to grips with making the main datum face for the whole engine. What is required is to clean the surface off to remove all hi/lo spots. I found that taking a cut of 0.005" was enough to achieve the goal.

Once that flat area was completed, I jumped over to the cast in recess, and because it was full of lumps and bumps, I cleaned the whole lot up to make it look more presentable.

This is the finished result, all ready to have the bearing holes drilled and bored in the three uprights.

Now we are getting somewhere.

BTW, I was due to be building a magneto in parallel with this engine, and the pre production kit turned up today. But because I also have another little job to do as well, that build will now be delayed until at least next week.
There are only so many hours in the week that I can work.

Bogs

Bernd:

--- Quote from: bogstandard on January 18, 2011, 12:07:29 PM ---Bernd,

I had already measured up the bosses beforehand as best I could, that was the reason for choosing them. Before mounting up, I tried them on the upstands without any screws, and as there was no rocking at all, I left them as they were.

If I had tried to level them with a file beforehand, I could have been playing about for hours trying to get them into a no rock situation.

I took it as a 'leave well enough alone' situation.

As it turned out, when measured from the new datum base to the top of the bosses, they were all within 0.002", so to me, to get a casting that close at this stage of machining is doing rather well. The more small datums that are cut, those measurements will get even closer.

Bogs

--- End quote ---

I had kind of figured that, but was just curious. I know you won't skip an improtant think like that. Talk about luck being on your side.

I'm following this very closely since I'm getting that urge to work on that bottle engine again, but will wait till your done here with this build as I'm re-learning a few things I had forgotten from work.

Keep up the great work.

I'll be quiet now.

Bernd

madjackghengis:
Hi Bogs, I got a look at the plans of that engine and it looks like she ought to be a good runner, with very good control over speed and power with gas. In looking at the flywheel of that engine, and that of mine, I think I've got to shed a lot of weight, mine's only a 3/4 inch bore. Is the base plate gun metal as the spec sheet says? I can't tell from the pictures on my computer. It looks like things are going into place nicely, the jig plate idea worked well, and the casting straight. I like castings because they work, save metal, and look good when they're done. In my opinion, they are there for my convenience and savings of metal, machining is for purpose, and straight fitting parts, correct clearances, and reasonable fitment of parts need no excusing, I just hate when things are done to no specific purpose, and no excusing improves the look or finish then. That casting was rather well done for the hopper area to clean up completely with only five thousandths cut. It's good to watch it progress steadily. :beer: cheers, jack

Bogstandard:
Bernd,

Maybe it was a bit of luck with those bosses, and the ease at which I managed to get the baseplate level on the bottom, but it is like everything when working with castings, you have to get that initial datum, once that is done, everything else becomes a lot easier.

Some people can just grab hold of a casting and find the datums straight away, unfortunately, I can't do that, so I have to work out everything the hard way. Even though it looks difficult, it isn't really, it is just a matter of sitting down and looking at it logically, the answer is usually staring you in the face.

I don't want to put beginners to casting machining off by what I am doing. It all looks very complicated, but during a conversation with a friend on Skype, I mentioned that even though I have posted a lot already about it, there is only about two hours actual work that has been done. So in fact, it isn't too complicated at all. The act of writing and posting about it makes it look more complicated than it really is.

Jack,

This engine, as far as I know from the plans was dated 1994. It initially called for a gunmetal base, but due to time and of course costs, it now comes with a cast iron base. The water hopper though is still a very heavy gunmetal casting. It's such a shame really, because I have it in my head that I am going to paint it, not polish it, after the initial runs are carried out. I will have to see whether the burner will take the paint off before making my final decision on that.

I wouldn't worry too much about your flywheel being overweight. These engines need as much help as they can get, and having too light a flywheel could stop it running.

Also having looked at the plans on this engine in detail, if you didn't want all the curvy bits to the water hopper (but you could put them on if you wanted to), it could very easily be made from ali and cast iron bar stock, with the uprights being bolted onto a baseplate from underneath. After all, this engine only has three castings, baseplate, water hopper and flywheel, everything else is made up from barstock and commercially available bits.

John

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