Stuart 10H build

Home Model Engine Machinist Forum

Help Support Home Model Engine Machinist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Hi Geoff. Wow that's a real beauty you have build there! Thank you for posting the pictures, I like it! It will be hard to beat your and Harold's engines but I will do my best ;D
I do not understand the purpose of having 6 bolds instead of the mentioned 5. I will read the build log in the link you mentioned, maybe it will be clear after reading. For now, I see in the plans that the covers on both sides have a small flange that should keep things align properly.

Have fun the in the shop, best regards Jeroen


I just think 6 bolts look better and are easy to align to an edge.


The six cylinder crank looks great. I don't have a build log for my engine but there are a few photo's towards the end of Harold's Topsy-Turvy thread. Harold has some great photo's of turning his crank between centres early on in his thread, could be worth checking out. I think the cut from solid topsy turvy crank would carry directly across to your Stuart build.

You probably already know all this stuff, but just in case.

The Topsy-Turvy crank is made from a piece of flat plate and a pair of saw cuts are run along what will form the long rods either side of the crank webs. This is to minimise any distortion. I did mine with a 6mm roughing endmill as I couldn't be bothered sawing by hand.

Also it's important to use what they call "hot rolled steel" in the US. We call it "black steel" in Aus. "Cold rolled" or "bright steel" will probably distort too much. Finally grind the middle out of the tool for turning the crank pin, so it only cuts on the corners. Then take light cuts with it.

I'm sure your crank will come out great, cutting from the solid is lots of fun and the way to go.

Hi Steve, checked your and Harold's work, looks very nice, compliments :bow:
Also thank you for the time of writing your advice down here, its appreciated! I do not have flat stock available, I will make the crank out of 30mm "automaton staal", I do not know the English term for it, it might be free cutting steel. It has an addition of lead inside so it cuts very easily and gives a nice finish. Its not very hard, but I will not run the engine so much so that would not have to be a problem. That's the good part of constructing a crank, you can use silver steel.
I really feel I can get this one piece crank thing done, just be careful about distortion as you mentioned. I think for this first attempt I will do all in the lathe, I have, correction, will make time for it, do not want to have a failure because I cut away too much material in the mill. Probably the next one I will prepare on the mill and finish in the lathe.

I did a little in the shop, will post some progress soon.

Regards Jeroen
Thanks Jeroen

So are you going to CNC turn the crank? You'll need to take lots of light cuts

The leaded steal sounds like 10L14. If it is bright drawn and you have access to something suitable, you could consider annealing it first, just to minimize any distortion.

Jeroen - I agree with steve regarding the material you are referring to. Over here in the US we have what we refer to as 12L14 and 11L17. We also refer to them as "Ledloy".
They are used for screw machine work because they are free machining and give a good finish. My flywheels are always made from this because their are easier to machine. The only problem is they are cold rolled and there are stresses inherent in the material that can cause warpage on larger parts. For this reason I always use hot rolled steel which we refer to as A36. The site I am giving you has material sheets on almost all of the metals that we commonly use here in the US including brass and the different grades of aluminum. I find myself referring to it a lot when selecting materials.

Here are some links to the steels I am referring to:

I am enjoying your build. Keep up the GREAT work!!!


Thanks Geoff, clear for me! I think I will keep the original 5 holes, in a way I prefer "original". Never the less thank you for your input, its appreciated!

Steve, I will do this manually on the lathe, I use CNC for 3 reasons:

1) Complex shapes
2) I need multiple pieces
3) I just want to use (play with) CNC

For this single crank its much quicker to it by hand then to make the G-code, test, modify, test again, etc. Further I am not a big fan of using a parting tool in CNC, I always find it scary to feed it straight into the material.
CNC is not a wonderbox, in most cases (at least in mine) it needs tuning especially when high accuracy is required (+/- 0.01mm).

The only thing I have available is a propane torch. I will try to use the material as is, let’s see what will happen. Thanks for the tip anyway!

Thanks for the additional information about the materials Harlod, its very useful to me and I am sure that it will be useful to others as well.
I have never bothered about material properties too much, I guess in future I should. Normally I use what I have on hand at that moment.
The good thing about the lack of knowledge is that you are not bothered by that knowledge! As mentioned I will use the material as is and see what will happen.
The material is already in my shop for some years, maybe its already relaxed (assuming that being in the shop has the same effect on the material as it has on me :big: ).

The more I think about, the more I am looking forward to give the crank a try.

Regards Jeroen
Well nothing like a good old experiment to separate what is fact and what isn't. I'm looking forward to finding out what happens :)
Thats what it will be Steve!

Here's the progress on the 10H. I wanted to have the 16mm hole drilled in the sole plate and wondered how to make sure that it would be as good as possible perpendicular to the crank. I decided to first run a 10mm radius mill trough the bearing holders and use that as reference to set-up the sole plate for drilling.

Started with finding the middle of the bearing holder with my new toy. During the build of the lathe my TNC121 broke down and I found another Heidenhain on internet for an reasonable price. It misses the axis feed function (+/- 10V analog output) but it has some great other features. It came with an original probe and 2 glass scales.



I took a hard metal ball nose mill of 10mm and run it trough the middle of the bearing holders


Now I have a reference for setting the sole plate on my angle plate to drill the 16mm. I used a 10mm bar and 2 parallels to adjust the sole plate such that the boring will be perpendicular to the crank and when in position clamped it firmly



I drilled the hole using end mills, they will not be distorted by the cutouts in the side of the sole plate. Started with a 15mm roughing mill and after a 16mm finger mill.




Unclamped the sole plate and........ :eek:........failure.....


I checked my mill since I was afraid that the hole was not straight drilled. All my axis X, Y and Z are within 0.01mm over a length of 150mm, so that can not be any issue. The only conclusion I can draw is that I messed up a dimension when setting the center, still do not know how it happened, but it happened! Ok, the center is 1mm off on the backside, from the top side it looks quite ok.


Luckily I have a 17mm end mill, that should be useful to correct the drilling to the proper position. I took a long (known to be straight bar) and chucked it up in the mill. I used this to find the exact middle between the 2 bearing holders and when found I was indeed 1mm off in relation to the original boring I made. At least I considered myself lucky that all dimensions came together. Next time I will use this method before make the first drilling :-[


Run the 17mm end mill trough and with sweat in my hands released the clamps to look at the result. Not too bad, at least I am happy again!


Thats all, thanks for watching and have fun!

Regards Jeroen
Nice save, just don't forget to make other bits to suit. I hate the idea of buying a casting then turning it to scrap, scares me a bit.

Hi Brock, thanks for the reminder! I already changed the dimensions of the related parts straight after drilling 17mm instead of the desire 16. I am not afraid to ruin a casting, if it cannot be rescued you can always buy a replacement part. I consider it learning money and the painful truth is, the more it hurts in your wallet the better it will stick in your brain ;)

Regards Jeroen
Nice save on your part. Sometimes it isn't the money as much as a person's pride. I have messed up parts and then spent probably more time than to just remake it figuring out a workaround.

You could have just shown us the finished part and we would have never been the wiser. Kudos and a karma to you for sharing your mistakes.

I know exactly what you mean Harold! Normally I screw up when I am in a hurry and spend more then double time in correction of the error. I hoped when I got older this would become less, unfortunately I am still waiting..... ;D
Hope by posting my mistakes that besides me other people take their advantage from them! IMHO I believe that's why we are here, to learn, to share and have fun ofcource!
Thanks for your replay and karma!

Regards Jeroen
Hi Guys,
The clever chaps learn from their mistakes, the really intelligent ones learn from other chap's mistakes. That way it's also cheaper! ;)
Thats so true Ned!

Hop you all had a good Christmas and that Santa was very generous to you with new tools and toys….

I have been struggling with the sole plate, one side of the casting is really hard! Its not just a thin layer and I tried to heat it up cherry red and let it cool down again. Did not change any thing… :-\

Below my progress on the 10H

Tried to mill the top of the bearing holders to the correct height. One side went very well, the other on did not cut at all. As you can see it breaks the material instead of cutting it. I do not have a carbide tool, costs me 2 end mills…..nice material to practice with my tool grinder…..


Next I made the inner radius to 11.1mm with a carbide radius mill


Below my setup to drill the bearing mounting studs


Again I struggled with the hard spots, try to heat and cool down again but it keeps being too hard for the tooling I have available. At a point I had enough and took the decision as you see below


Took a piece of 10x10 mild steel, and prepared it for silver soldering


Then I start shaping the mild steel



Drilled the holes (and tapped 7BA) for the bearing mounting studs and tapped M2.5 for the oilers


Did some more shaping to the mild steel:



Next was to get the correct angle of the casting copied into the mild steel part




Cleaned up the inner side and and the slot on the side of the sole plate



I am glad I took the decision to remove the hard part, its too expensive in tools when you do not have the correct ones available. After painting this operation will not be visible anymore



Remaining are the clean up of the cylinder mounting and drill the 5 mounting holes. Then I will start on my crank.

Have fun in the shop, regards Jeroen

You did a nice repair on the casting Jeroen. It seems from some of the other postings that the Stuart castings are having the same problems. I guess personally for the money you pay I would have sent it back to them for a replacement. I have had problems in the past with the valve covers but never on a large casting like the base.
Yeah, I've been having some problems with hard spots in some recent Stuart castings too.

Very bold of you to just mill off part of the casting! I think I would have waffled about doing this for far longer! I might also have considered milling off both bearing supports, and just making the bearing supports larger (in the style of the Stuart Beam) and perhaps from bronze. It would change the look, but it could work.

I'm following the build with interest!
I have heard about hard spots in the new Stuart castings also ,I never had a problem with the old castings so before the old company went out of business I bought two casting sets of every engine in the catalog , my father thought I was nuts for doing so .
Great job on the repair.
George, sending the casting back seriously crossed my mind. But then I start to think about all the hassle, waiting for who knows how many weeks to get the replacement part....I would not like to have my project down for that time and the solution was relatively simple.

Smfr, its not so bold after all, just struggle and demolish the tools you have in stock, then these kind of decisions come quite naturally to me ::) Thanks for putting the topic on hard spots, I really got some good tips from there. The fault I have made is that after having it heated to red it cooled down too fast. Next time I will put it in the fireplace (I assume (and hope) it does not get soo hot that the casting will be damaged) and my wife also will be happy since I put the fireplace in the living room instead of spending time in the shop ;D You are lucky that you just need to get a hole in the valve body, if it needed to be treaded afterwards a carbide drill would just solve half the problem. For the sole plate I do not take the risk of heating it again and loose my silver soldered work, keep my fingers crossed for the remaining machining of this part. Keep on the good work on your beam restoration, you are doing an excellent job there with a very precise finishing of your parts!

Jeff, I probably would agree with your father before, but after this week I would say an expensive but pretty smart move!! It seems that the Stuart people are in a hurry these days and do not let the parts cool down properly or they put a lot of junk in their foundry. Hope to see some of them build by you very soon over here!

Regards Jeroen
I have been watching this build with great interest. I got the castings for a no9 given to me a few years ago and i am just waiting for my skills to get better before i attempt a project like this. Yours is looking great and good repair job on the one casting.