My Little Donkey

[Jasonb]

I first saw one of these engines on e-bay 3-4 years ago, liked the look of it so copied the images to my "Future Projects" file though I did not know exactly what it was. Over the years a couple more have cropped up on the same site and one of those included a copy of a page from an early Bassett-Lowke catalogue which gave a couple of sizes as well as a description



Using one of the photos that had a reasonably square on side shot I imported the image into Alibre and scaled it to suit. I could then take sizes off of that to produce a replica, this time in metric and I kept it about the same size with a 16mm bore and 15mm stroke.



It was done using a mixture of silver soldered fabrications and cutting from solid. Mostly on the manual machines though I did use the CNC to cut a couple of parts that form the frame and also do the flywheel from a slice of 80mm CI bar.

It's the first engine I've done with a Scotch Yoke so that's another notch on the workshop door frame. Seems to run quite well on a few psi and even pumps though I think some house training is in order.



<a href="https://www.youtube.com/watch?v=T871NGafEAo" target="_blank">http://www.youtube.com/watch?v=T871NGafEAo</a>

[Jo]

Cute little engine  Is this actually going to be a build or another showcase of your completed build Jason?

If it is not a build it needs to be put into the showcase area.

Jo

[Jasonb]

Who knows how the thread may develop, if someone askes me about how I did a certain part I'd like to be able to answer here.

Besides it does not mention "build" for the own design topic

[Jo]

For the avoidance of doubt the engine section is intended for members to post their build logs.

The showcase section is to enable people to show off the models they have built without detailing the build. If other members enquire about aspects of the build of a completed model that can also be included in the showcase area.

Jo

[Vixen]

Jason,
This is a fine looking engine and beautifully presented; no matter which category they eventually decide to place it in.
Mike

[Jo]

To avoid other people getting as confused as you seem to be Jason I have updated the forum layout to include the words" Post your build logs in here" 

Jo

[Bearcar1]

Ouch! Jason, "Mammie Yokem has spoken" (from an American western movie) ... Anyway, that is one heck of a cool looking engine, and I good runner. Would/could you share the drawing sets or roughly dimensioned drawings with us?


BC1
Jim

[Jasonb]

Thanks Mike and Bob.

I'm not sure you would really want my "drawing set" as I tend to pick what I need off the 3D parts and take a rough sketch to the workshop, this from another of the small engines



Even my rough initial pencil sketch has had changes made as the design developed



But if you can open current Alibre files or pick the parts out of a STEP file of the assembly then drop me an PM with e-mail address. Having said that I nay do some proper drawings as I have also been asked elsewhere for them. I also want to stretch it a bit as the crankshaft could go a bit higher to make a bit more room for the pump.

Either way it would probably help anyone wanting to build it for me to describe at least the major parts so looks like Mammie will have to leave the post here.

[Jo]

We are looking forward to hearing all about the build 

Jo

[Dave Otto]

Nice little engine and pump Jason!
Another project well done!

Dave

[Jasonb]

We are looking forward to hearing all about the build 

Jo

Could it please be moved back to the build section of the forum then.

I won't do a bit by bit build description but will try to cover the main parts subject to what photos I took

The frame seemed the most logical place to start as that was the most complex so any deviations from design that may result could be gotten out of the way and  the design of other parts altered to suit rather than having to remake or modify them, In the end that was not really needed. I tend to design my fabrications as a single 3D part and then pull off the details of the various sketches and extrusions that make up the part as individual pieces.

Starting from the bottom a piece of 5mm sheet was thinned down to 4mm, taking equal amounts off both sides, then milled to the required length and width. To help locate the other components some 2.5mm  x 1mm deep slots were milled and the holes for the mounting screws and pump ram body drilled



Although they would not be too hard to shape by hand I made use of the CNC to cut the shape of the 3 pieces of 2.5mm steel that make up the majority of the frame. Once cut I put some more slots in on the manual mill and also squared up the internal fillets left by the 3mm milling cutter on the CNC with a file so they would drop into the slots. Bending was done after the machining was complete, nothing fancy just a piece of round rod in the bench vice to give the desired radius and bent by hand.



The cylinder mounting flange was just simple turning and I left it over length and over diameter so it could be finish machined after assembly. A piece of Culphos had a spigot turned on one end to locate in a hole in the vertical leg of the frame and was thinned in the middle. This thinner area will get milled away but it helps to keep the two bearing pieces lined up if they are soldered as one piece.



The parts all slotted together quite well and I only used one loop of soft iron wire to hold a couple of bits together though I did decide to solder the cylinder flange on as a second heating.

Here is the rest of the soldered frame having the location radius for the flange machined as it was easier to locate at that stage than when all the bits were separate. The main clamping is down to the mill table but I added an angle plate and a clamp to reduce the chance of any chatter while plunge cutting to form the radius.



After soldering on the flange a similar setup was used so that the OD of the flange could be "turned" concentric to the hole for the pump ram body using the boring head and the thickness brought down to finish size ensuring it was at right angles to the vertical axis of the engine and the hole for the piston rod gland drilled and reamed true to that. Cylinder stud holes were the last things to do to the flange. I also used a long series non ferrous specific milling cutter to face the ends of the bearings to length.



The final job on the frame was to set it up on it's back so that the two bearings could be drilled 4.8mm and then reamed out to 5mm diameter.

[Vixen]

Jason,

Some very interesting fabrication techniques in use. I love fabricated 'castings'.

Much more satisfying to make than simply buying a a ready made casting.

I needed to make a lot of this type of fabricated 'castings' for my Fowler PE.

Mike

[Admiral_dk]

Fasinating ways 'to Divide the Part up' in several pieces 

Hopefully inspirational to others 

Per

[Jasonb]

Thanks for the interest guys.

Some very interesting fabrication techniques in use. I love fabricated 'castings'.

Don't let Surus hear you saying that, you may get excommunicated

As you say there is a lot of satisfaction to be had from designing the "casting" allowing for how you will fabricate it as well as the actual fabrication. You also get a lot more workshop input per part which stops the completed models piling up on the shelf at too fast a rate. Take that frame as an example, if a casting it would just have wanted it's bottom smoothed, bit of work to the flange and then face and ream the bearings. Doing the fabrication probably took at least 10 times longer  and was a lot more enjoyable and challenging.

I doubt I will get the interest back to build up the Superba that I have castings for but if I di I know a lot of those castings would not now be used. Even Jo started to build up her bearing and ploughing shaft brackets but unlike me she got lured back to the casting mountain from where I fear she will never escape

[Jo]

Good start to explaining the build JB. Looking forward to hearing more about it - like you can explain things like the Scotch yoke design to the members as they may not be aware of its simplicity.

And like Uncle Perce said to me every year the new comers to our hobby are starting from scratch so you have to explain everything to them from how to correctly open the packet of seeds to digging over the vegetable patch - it is all obvious to old hands but even they can learn a new trick or two if things are explained in detail.


Yes I started putting together the pair of brackets for my BB1 but fabrication takes ages and on really complicated pieces made up of a dozen parts can be soul destroying. Alternatives like CNC from solid are available.

Jo