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[Flyerjeff]

Hi,
I have a Clarke 300M variable speed lathe with optional extras; 4 jaw independent chuck, fixed steady, travelling steady, revolving tailstock, 6” faceplate and tailstock chuck. A very good lathe, apart from
the plastic gears, they tend to strip on the keyways, I have put steel inserts in the centres of the gears which has cured the problem.
I have a Clarke CDM 10 Micro milling machine, does everything I want no complaints with this machine.

I have looked up the details of your Sherline Lathe Mill, I don't see any reason why you should not be able to build a Stuart twin on this lathe and mill.

Regards Mick

Thanks for the quick reply

[gondolier88]

Hi Greg,

Yes, I must admit I was very disappointed with the casting set considering what they cost and extra materials needed as I have told Stuarts, your web site is misleading in the description of the casting set.

The paint is Japlac British racing green.

Mick

Hi Mick,

Thanks, I'm very impressed with that paint.

You'll have to let us know what they come back to you and say.

Greg

[Patternmaker]

Hi Greg,

Stuarts have now changed their Engine Description, ( No bar stock materials supplied with the kit)  no help to me but at least it will let other purchasers of this casting set aware.
As I purchased from another source, a lot cheaper than Stuarts and have a good stock of materials it is not a
problem.

I do consider this casting set expensive for what you get although I must say the quality of the castings are
excellent.

Mick

[gondolier88]

Hi Mick,

That's something I suppose, as you say no help to you. You seem to be managing just fine however Keep it up- you'll be onto the next project in no time at all, some people make me sick!

Greg

[Patternmaker]

Cylinder block completed, quite a few changes from original design.

[kno3]

What's the reason for the peculiar placement of the screws on the cylinder top covers?

[Patternmaker]

What's the reason for the peculiar placement of the screws on the cylinder top covers?

Spaced as shown on the plans, they have to be in those positions to clear cylinder Exhaust ports & drain cocks, as you can see from an earlier picture they are spaced the same in the bottom cylinder covers.

[ooyah/2]

 Kno3
Another reason is that as the pistons are set at 1.25" centers and are 1" dia it only leaves a bridge of 1/4" between the bores in the cylinder so you have to cut the cylinder covers to fit and use a common bolt in the middle.
George.

[kno3]

Thanks but I didn't mean the shared screw between the covers. I mean the bottom 2 (on the exhaust side) that are much closer to the shared screw than the others, those don't seem to have to clear anything below, so why aren't they placed as to be at equal distance to their neighbours?

[Patternmaker]

kno3

The cylinder casting is different on the exhaust side, if the cover bolts were equally spaced there would only be an 1/8” depth of thread in the casting, which as you know would easily strip being cast iron.

Mick

 

[oLiV]

Hi from france, I was following this topic, and I'll try to reply as best as possible, please forgive any bad english:

I'm actually building a Twin Launch too, and I decided to make some changes to the original drawings for cosmetic reasons. one of these is to drill the top covers' holes equi-spaced (72° from each other). I've not done it yet, but I see no reason why this couldn't be done. There are also several examples on the net.

[Patternmaker]

oLiv, I hope you are enjoying your build and wish you good luck.

Mick

[oLiV]

Thank you Mick.

I'm a beginner in machining, I'm actually collecting tools and learning about using them ! And trying to get familiar with imperial sizes  

my mill is a HBM SX1 (the same as the Clarke CMD10) and my lathe is a "big" Fartools ML350 my father owned.

Olivier

[ooyah/2]

Hi  Oliver
I look forward to your build, please post some pics.
I also am considering a launch engine build.
George.

[oLiV]

Ok, I'll post a new topic soon

Olivier

[Patternmaker]

Oliver.
Is the picture you posted pf the Stuart Twin from RC groups.com built by dunc 2504 from Somerset, if so he says that he has only run it on air, nothing else since from Aug 2010.
This is the only other example I have found with equi-spaced cylinder bolts, there is a fine line between cosmetic changes and practicality.
I'm sure that if it was practical to equi-space cylinder bolts Stuarts would have done so in their original design.

Mick

[oLiV]

Yes it's Dunc's engine. I didn't know he had never steamed it.

Another example :

[ooyah/2]

Oliver ,
I must caution you about these bolt positions, as you say that you are a beginner to machining I would advise you to stick with the STUART drawing.
If you space the holes equally it means that on the 2- bolts in question it only leaves you 1/8" thickness of cast iron to tap into where as if you go by the drawing you will come into solid cast iron.
Now if you don't know cast iron is not the strongest material to tap into so you risk the possibility of stripping the thread if you over tighten, so I would advise that you stay with the drawing as it has a purpose more than cosmetic but of course that is entirely up to you.

George

[Patternmaker]

Eccentric rods, Reversing quadrants and link rods

[south steyne]

 :-)Look great my only concern would be the depth of thread on the eccentric journals but that's just my thoughts.
John

[south steyne]

Sorry maybe I can clarify a bit better as I see by the drawing the crankshaft appears to be 1/4 in, so the thread depth for the set screw would be probably only abut 1/8th and as these eccentrics need to be tight I would think a better way would be to drill and tap into the main body of the eccentric and double set screw after you time the engine any other thoughts welcome
John

[Patternmaker]

John,
The crankshaft dia is 5/16” When the timing is set the eccentrics and flywheel will be taper pined to the crankshaft.

 

[ooyah/2]

Hi Mick,
Taper pinning the eccentric is a bad idea, once pinned it's there for ever.
If for some reason you have to look at or alter anything you are snookered and it's going to be a tricky job to drill and pin after the engine is built.
How would you hold the completed engine steady enough to drill and ream.
If the drawing calls for pinning, pin it if not leave it as there is very little strain on the eccentric sheaves on the shaft.
As the eccentric sheaves are steel there will be enough grip with a socket  grub screw.

George.

[derekwarner]

 ooyah/2...I do not necessarily agree that taper pinning is a "final solution..........& cannot be revised/altered from a timing perspective" 

Most of the British designed mechanical gun control computer systems [pre & post WW1] had small backlash compensated gear drives that were aligned & secured by BS Standard taper pins

Some of the beauties of such fastening devices was that they required no heat......no liquid adhesives....would never vibrate loose ....   but were still easily removable & easy corrected from a timing perspective simply by rotating the componet to be re-timed & re-reamed

Another positive characteristic of the tapered pin over HPGS is that diametrical clearance between mating parts is not savagely distorted    which is important with high speed & balance ....Derek

[Patternmaker]

George,
 
This is what I meant by a tapered pin, 3mm stainless steel socket set screw, I will also use it on the worm drive for the boiler pump.
I have used this method on all my sports boats for flexi drive couplings for many years.
 
Mick