Coles C-611

[Jo]

Thanks Guys,

I found a horrible hole in the port face:



I have had a poke around in the hole to get rid of any sand and filled it with JB weld. To allow me to continue I have put a piece of Sellotape over the wet JB Weld.

The cylinder has been mounted in the centre of a rotary table (BCA Built in rotary table) with the port face nice and square to to milling machine axes and the four 4BA mounting holes drilled and tapped:

 

We now need to round the outside of the cylinder. First check with the cover to see how much may need to come off



- not a lot  So with and end mill going round the outside cut the face the diameter of the cover minus twice the thickness of the cladding:



Once one end is done the cylinder is turned over and the other end rounded before drilling for the cylinder cover mounting studs:



Tap the cylinder for the screws:



I also clamped the cover on the end and drilled for the mounting holes in that while things were all nicely set up 

Lets have a look at what we have with some screws in place:








That looks ok

Jo

[crueby]

Coming along great!  Good thing that hole was off to the side, not on the leading edge of one of the ports!

[Admiral_dk]

Very nice work and explanation Jo 

Deadlines .... some are W..k and some are personal - like getting the big bike back on the road, as John (my brother in Law) is getting impatient, about us starting to go riding in the countryside again 

[Jo]

Thanks Guys 

In between doing a load of compost sieving  I needed something simple that needed little thought to do while my back recovered before doing the next lots so I decided to start roughing out the crankshaft. This is the crankshaft:



I am not sure if this is the original casting for this engine as it is well over sized. A quick check against the soleplate:



The crankwebs will need to be made narrower and they also seem to have lots of material on them  Where do we start? We are going to put a centre in either end of the shaft using a centre drill. To make sure the drill goes into the centre and true I have used a hand punch and have squared up the casting:



Now we can mount the crankshaft casting up on the lathe between centres. You can see that I have wound the top slide back - this is because the saddle would have hit the tailstock otherwise and I don't want the tailstock pointing out any further than need be.



The crankshaft is being driven by a dog, which is pushed round by the pin on the drive plate. You can see I have wound an elastic band round the dog and the pin - this will stop the dog coming off the pin during interrupted cuts:



Now we can spin up the lathe and see if the casting is shaped like a banana:



This one is ok 

I am using a carbide tipped tool as cutting this is going to be hard work on any tool until we get under the skin of the casting. I am cutting on the right hand end of the crankshaft away from the nose of the lathe and looking to to skim the shaft surface before doing the right hand side of the crank web:



Lets look at the turned surface:



Yes it is horrible. The arrow is pointing to rough bits caused because the casting is hard in those positions. This is something known as chilling. It is caused when the casting was cooled too quickly after the metal was poured. Normally it is only on the surface 1mm or so and there is 6mm to come off the diameter so it won't be a problem (famous last words  ) If it was really, really hard the trick would be to heat up the casting to red hot hold it there for some time and then let it cool slowly - this can easily be done in a bonfire or as Surus does over night in our log burner 

With the first end having had one cut:



It is time to turn it round and do the other end:



That is as far as I have got so far as I have run out of compost to sieve.

Jo

[crueby]

Quyite a big chunk of casting to trim down, though it sounds like its good they left the extra material to take the outer skin off. I was wondering why you did not put a spacer between the webs to keep the center from flexing in - is it since the webs are so thick that it was not needed? I'm used to doing smaller cranks that need the extra packing.

[Jo]

Its very thick Chris. The shaft needs to be 9.5mm diameter and its over 16mm thick including the bit for the pin. This isn't going to flex 

Jo

[rklopp]

Is the crankshaft made of ductile (modular) iron. I see curly chips instead of crumbs like one gets with gray iron.

[Jo]

It feels like some sort of steel casting. I don't have the drawings Coles just says "Iron Casting".

The other cast Iron castings are very grainy same as I found on the bigger Coles Horizontal Steam engine.

Jo

[Jasonb]

The SG iron or ductile iron as they tend to call it in the US does machine more like steel than grey CI, can have an odd smell too sometimes. The ** GT inserts for aluminium can give a nice final cut on it if it starts to play up as the diameter comes down.

J

PS You can come and sieve my heap if you have nothing better to do

[Jo]

PS You can come and sieve my heap if you have nothing better to do

Sieving compost is good exercise for you  Mine is all done now  Until the Autumn when the next one will need doing.

Was given 3 bags of "commercial compost" - the stuff the council generate. Its nothing like well rotten compost  Looked more like minced garden rubbish. I had a dozen spare cue plants so I have stuffed them in it to see if it is actually any good.

Jo

[crueby]

PS You can come and sieve my heap if you have nothing better to do

Sieving compost is good exercise for you  Mine is all done now  Until the Autumn when the next one will need doing.

Was given 3 bags of "commercial compost" - the stuff the council generate. Its nothing like well rotten compost  Looked more like minced garden rubbish. I had a dozen spare cue plants so I have stuffed them in it to see if it is actually any good.

Jo

Sounds like it may have been Politician-Exhaust - eewwwwee!      

[Jasonb]

I always worry that the council stuff will contain weed seeds even though they say the composting temps are supposed to kill them. I know all my weeds go into the brown garden waste bin they empty, only good green waste and the odd amount of shredded shrub cuttings go into mine and the kitchen stuff too.

[Jo]

I left the crankshaft with the first side rough turned circular so it is time to finish off the turning. This end I am going to turn to dimension (the other end is still over sized). I initially turned it using the same roughing (second hand tip) then swapped over to a new stainless steel cutting tip which gave an acceptable finish.

With the shaft 0.5mm over diameter it is then time to take down the faces of the crank web:



There was nearly 3mm that needed to come off. How I worked this out was: I knew the overall width I was aiming for (25.4mm), I knew what the width actually measured 31mm, I could measure the gap in the middle and I knew what thickness I needed for each web (6.35mm). At this point I am ignoring the inner gap dimension in so far as I need to leave enough so that each web can actually be 6.35mm thick (easily done if you take too much off one side  )



Having faced one side to where I had decided that face should be it was time to do the final cut on the diameter of the crank shaft before turning round and repeating: take diameter slightly over sized, do face, then take to final diameter. If you take the diameter down to the correct diameter before doing the face you are likely to end up with ridges alongside the webs 

Now for the crank pin:

I have mounted the crank in my crankshaft turning jig, you could probably use a 4 jaw to do the same. What you should watch is that ideally you want to hold the crankshaft next to the web to minimise the amount of flex (I learnt all about crankshafts flexing when I did my triple cranks  ) As you can see I have made up a crank support that has one hole the diameter of the crankshaft and a centre drill spaced at the throw of the crankshaft - this was used to position the crankshaft on the face plate and secure it as well as a support for use during turning.



You need a long parting off tool to turn the crankpin: One that won't be hit by the webs as they spin round. Always check everything is well clear before turning the power on - you never know what may hit on these types of turning jobs. Now we are going to start by cutting either side square:



With both sides just over thickness the central pin can be turned. Note that you should "plunge" the cut nearest the left hand side and turn  the material off towards the right - this is because there is less likelihood of any flexing nearer the holding jig/chuck.



Then carefully you can take the pin down to diameter - remember as the diameter reduces the greater the chance the crank will flex. This means you may need to reduce your cutting depth to avoid flexing which will end in  failure. In the end the crank is down to diameter and we can take a final skim off of each web which brings them to thickness:



and now we can have a look at the crankshaft in the soleplate casting:



Before squaring off the throws I need to have a look at the crank balance weights.

Jo

[MJM460]

Nice work on the crankshaft, Jo.  Thanks for posting the detail of all the steps.

I am really enjoying following and learning from this build.

MJM460

[iRon]

Thanks for showing the crankshaft machining, Jo. I am learning!

Ron