Is There Time - The Build of Willy.

[vtsteam]

Very clean design and execution -- a trademark of yours, Jason. Elegant simplicity! 

[Jasonb]

Those that have been following my Kelsey thread on ME Forum will have seen that I had thoughts of a single cylinder version but was a bit put off as most of the work would just have been a repeat of the Vee Twin. However I have a large folder on my computer of “Future Projects” and one image that I have had stored away there for a couple of years is this little wobble. I think it may be an early Stuart from the days when they had cast cylinders not the current extrusion as the screws would have gone into the cylinder flanges rather than the long studs used on the extruded one.



A bit of time spent on Alibre and I had a design that I was happy with and decided to upload the frame to Craftcloud just to see what a 3D metal printed one might cost as an alternative to making it by fabrication.



The price looked reasonable, so I went back and modified the frame file to be more like a casting by suppressing all the holes and adding a small machining allowance. As mentioned earlier in the year in my A J Weed engine build a lot of the online quotes have a set “job price” that includes printing, post and tax and as this is quite a small item it easily fell within the job price. Playing about with the quantity required showed that I could actually get six frames printed for the same job price as just one so decided that was the sensible option as six frames for £37.00 seemed quite reasonable to me particularly considering that just one spare casting for the Stuart single ST would set me back about £43.00.

I then did a less sensible thing and deleted the quote for the pattern instead of deleting the one for the finished standard and did not realise until the prints arrived just 10 days later. Apart from the holes and no machining allowance I was happy with the way they turned out and after poking a couple of drill bit shanks into the holes was relieved to find they were all 0-2 to 0.3mm undersize. The material is Aluminium and I opted for a bead blasted finish.





With the prints arriving on the 29th December is set myself the task of making the engine before the end of the year so got my finger out in no particular order.

 

Standard.

After quickly rubbing the bottom over some Emery cloth laid on a tile I set it up in the mill vice using a close fitting drill shank to locate the crankshaft bore as my datum point. I took 1mm off the crankshaft boss and the lightest of skims off the port face plus a deeper pass through the middle to reduce port face friction.



The crank boss was drilled out from 3.7mm  to 5.8mm then reamed 6mm to take a bronze bush and the cylinder pivot drilled 2.8mm from 2.7mm before being reamed 3mm. The ctr to ctr distance was as drawn at 31mm.



Four plunge cuts with a 2mm milling cutter crispened up the edges of the steam/air ports.



Flipping the print the other way up the opposite ends of the crankshaft and pivot bosses were squared up.



Then onto its sides to run the 3.5mm drill in and then tap for inlet & exhaust M4 x 0.5.



The bottom was then drilled 2mm for some fixing holes, these had not been put onto the design at the time of ordering so were not present on the print.



Setting the casting up for the final sixth time the two linking passages were cleaned out to their 2mm diameter and then counterdrilled 2.5mm for a short depth so the plugs had something to stop against rather than block a port hole.



A length of aluminium was turned to fit the 2.5mm holes and two pieces cut off and Loctited into position to close off the drillings.


 

[Sanjay F]

"I think it may be an early Stuart from the days when they had cast cylinders not the current extrusion as the screws would have gone into the cylinder flanges rather than the long studs used on the extruded one."

I didn't realise they had changed, I presumed they were all cast - this is an old one I did up sometime ago, it looks cast when you look at the edge of the lagging?

Is that the same for the twin oscillators too?

[Jasonb]

Yes that is a cast one and has the screws to retain the cylinder covers which fit the flanges at each end of the cylinder.

This shows the extruded cylinders which have notches for  along stud to pass from one end to the other. I'm not sure if they have reverted back to castings as they seem to have done that on some of the other extrusions, maybe as stock runs out they go back to castings.

https://www.modelenginemaker.com/index.php/topic,9007.msg200744.html#msg200744

[PaulR]

Re the end of a thread being pushed up, I find it helps to put an under cut there preferably with a radiused tool, this gives a space for the die to run into, the tooth then having no metal to push up. Makes the thread looker neater in my opinion.

Braved the low single-figure temp in the workshop to do a quick experiment on some scrap brass. Ground a tool and turned a shallow groove where the thread would end and have to say it worked great and was easier than trying to undercut after threading as I've some times had to do in the past. The nut goes right to the end with not even the tiniest gap and the transition from threaded to un-threaded is bump-free - I'll be using this technique on all rods in future!

Sorry again for holding the thread hostage 

[crueby]

Another option is to drill/tap a hole in the end of the rod and loctite or solder in a short length of a screw. I like that option especially when the nut going on is thin, gives the most threads.

[PaulR]

Another option is to drill/tap a hole in the end of the rod and loctite or solder in a short length of a screw. I like that option especially when the nut going on is thin, gives the most threads.

Another great tip!

[Jasonb]

Crankshaft

As this was to be of built up construction an dLoctited together I did it fairly early on. The crank disk was turned to diameter, a short 1mm spigot formed and then drilled 3.8mm followed by reaming 4mm.



After sawing off it was loctited to a length of 4mm silver steel and left to go off. Once set the 4mm shaft was held in the lathe and the disc faced back to 3mm thick. Then over to the mill to drill 2.8mm and ream 3mm at a 6.5mm offset from the centre. I used a hand reamer for this (under power) and did not quite go all the way through as the taper of the reamer can be used to get a press fit. The 3mm silver steel pin was pressed in using the mill vice with a drop of Loctite for good measure.



Using a drill bit as a packer to get the same angle on both sides the disc was milled to give a counterbalance to the piston & rod. Just eyeballed nothing scientific. After test running I also added a small flat  on the shaft for the flywheel grub screw.



Crankshaft Bearing

A piece of 8mm bronze was turned a nice snug fit into the frame and then drilled and reamed 4mm. It was sawn off and faced to leave a 1mm thick flange at the full 8mm diameter.



 

Flywheel

A piece of 25mm nominal cast iron bar was turned to 25mm diameter and faced. I then used a HSS tool with a rounded end to form the 1mm tall spigot and also the recessed face. After drilling 3.8 and reaming the other side was faced and recessed but without a spigot.



Then into the mill to drill and tap M3 for a grub screw.

[PaulR]

"Once set the 4mm shaft was held in the lathe and the disc faced back to 3mm thick."

Brilliant. Why have I never thought of doing that to ensure perpendicularity?!

[Jasonb]

You mean you did not read all my other builds where I do the same

[PaulR]

You mean you did not read all my other builds where I do the same

The rate you build and post I have to speed read everything otherwise I'd never have time to set foot in the workshop 

[PaulR]

and... when using a drill bit as packing to mill the angle on the crank disc, how do you set it up to do the opposite side (and end up with a Dairylea cheese triangle!)?

[Jasonb]

Simply rotate the crank & disk in the vice so the pin is on the other side.

Same sort of thing in this thread
https://www.model-engineer.co.uk/forums/topic/v-twin-kelsey/page/2/#post-826496

[PaulR]

Simply rotate the crank & disk in the vice so the pin is on the other side.

Same sort of thing in this thread
https://www.model-engineer.co.uk/forums/topic/v-twin-kelsey/page/2/#post-826496

I thought that might be the case but even with your 3D drawing my brain is still trying to make sense of it, must be dementia setting in 

[Jasonb]

The cylinder follows much the same method that I used for Kelsey. It would come out of a piece of 25mm cast iron bar if the initial hole were offset but I had some 27mm material so used that without the need to offset the hole. I started by facing, drilling and then boring to 11mm diameter. That is a small 04 size insert you can see.



Then over to the mill to flatten the port face taking the height off an 11mm drill placed in the bore. That was also used to find the ctr line and equal amounts taken off each side to get the finished 14mm width. I also added the two 2mm steam/air ports and the M3 tapped pivot hole making sure to stop all three short of the bore.





With the cylinder now on end the ctr of the bore was found the 3 cylinder cover screw holes drilled and tapped M1.6. I also drilled a 2mm hole down to meet the port drilling and opened up the end with a 3mm milling cutter so it connected with the bore. repeat for the other end.



It was then the facetted cutting to get the final shape of the cylinder followed by a bit of filing to blend the facets into one radius.



Both end covers were cut from 25mm CI bar and the inner face done first complete with 0.8mm long spigots, one being drilled 2.8mm and reamed 3mm for the piston rod.



Rather than cut my soft jaws I went with a split bush to hold the only 1.5mm thick covers concentric and without wobble. After facing to length the top one had a decorative recess cut. I prefer a recess to a raised area as it makes painting easy with the higher bare metal surround easily cleaned up to leave the paint in the recess rather than trying to mask around a raised area.

 



The other one which was cut off longer had a spigot formed so there is some length to guide the piston rod. The one I based mine on did not have a gland so I did the same but the OD could be threaded and a gland nut added if desired.



The last job on the covers was to drill the screw holes.