1802 Bell Crank Engine

[kvom]

They are castings, best you avoid them 

It would be nice to get a set of Otto Langen patterns into the Foundary then my retirement casting sets will be ready and waiting for me

Jo

The trick is to figure out how long you're going to live in order to get the right number of casting sets.   

[Jo]

Best you get on with those BB1 patterns to go with them

That was the plan: have them finished to go into the foundry with the batch at the beginning of the new year 

The trick is to figure out how long you're going to live in order to get the right number of casting sets.   

I added it up the other day: stationary engines is about 10 years (11 years if I feel sorry for the one this Saturday), another 8 years of large model vehicles. But of course: I will have to buy more casting sets if I can convince work to give me early retirement 

Jo

[Jo]

Four feet machined 

They were nasty  They have been finished at 17.5mm long instead of the 16mm because if I took them any thinner the sides of the U-section would have had to come down to 1.6mm rather than the 2.4mm that I decided to leave them at.

To machine them I first machined found the level with the top of the U bracket and machined them to the 17.5mm width, to the top and machined the 9.53mm height, then raised the cutter to the 8mm to provide how far they stick out the sides. Then changing to a 3.2mm cutter found the same depth as cut with the previous cutter and then slowly faced the indie of one of the arms of the U to the required 2.4mm wide. that gave me a zero, then moving over 9.26mm machined the other inside face before stroking the bottom down to my chosen depth of 3.2mm which will be the face that is used to bolt the engine down with  .

That is it for this evening as I am off to buy some come-in-handies from my club's White Elephant sale 

Jo

[steam guy willy]

Jo, this may be the earliest engine that you are making, however,    better late than never !! I will be following this this with interest,  am still making the S&P with much fettling to do ,(should have adheared to the drawings) Good luck with the new engine.
Regards
William

semper rectam quote.........

[Jasonb]

So what elephants followed you home? 

[Jo]

   Only a few odds and ends: A rotary table that I think someone might be hoping to pinch off me, a few gas torch bits, some milling cutters, usual tat 

However never let it be said that I have to buy every casting that presents itself to me: I turned down two this morning that I need

Jo

[Stuart]

However never let it be said that I have to buy every casting that presents itself to me: I turned down two this morning that I need

Jo

Jo what is the world coming to you will not sleep well with such an imbalance in the force 

good build log as is your normal practice
Stuart

[Jo]

Thanks Stuart 

You are right I can see such thoughts driving me to  if I am not careful. Hopefully Saturday will bring things back to normal 

Jo

[Jasonb]

Bet you only turned them down as it would have required more moths than you were willing to let fly

[Jo]

The cistern needs a couple of little ears added to it onto which the crankshaft bearings will mount. These were machined out of a piece of 6.35mm square brass. First machined from the side to get a curved front:



Then on the top to give a square corner:



Drill a couple of holes and tap them for a pair of brass screws and the ears can be secured into place:



Sufficiently to then silver solder them permanently:



The condenser took the opportunity of joining us in the workshop while I waited for the cistern to cool. So first machine the top, using the central hole as the reference, once it had been skimmed, the sides were taken to size (of course one dimension was undersize again )



The underside was also machined then a quick check for the fit:



  I have been sent photos of castings 

Jo

[b.lindsey]

Nice start on the base Jo! Certainly an interesting engine too!!

Bill

[philjoe5]

Jo,
Just so I'm on board here....are the sides of the condenser supposed to meet the sides of the base?

Cheers,
Phil

[Jo]

Thanks Bill 

Hi Phil  When running the Condenser will get hot so you want minimal contact between it and the sides of the cistern so that the heat is transferred into the water in the cistern and not the body of the cistern. You can just about see the gap round the condenser on the full sized engine in this photo

I have just found out that the piece of brass that came with the casting set for the top of the condenser is under size so I will have to reduce the width of the condenser to suit 

Jo

[philjoe5]

Thanks Jo.  I'm not familiar with a cistern - condenser style engine but it's starting to become clear.

Cheers,
Phil

[Jo]

The pump started out as a big bronze casting.



It seems tempting on a casting like this to hold it by the big end and turn up the bottom  but the larger end needs to be machined first and left over size. This then gives the flat surface to go back against the chuck and provides a repeatable surface to hold by



Now we have something to hold it by it can be turned around, sadly it is too big to fit in a collet chuck so has to be protected by an aluminium shim from a drink can and held in a chuck. The casting is over length and all of the extra length is in the stem so it is important to use the base of the top as the reference and turn everything relative to that. As you can see there was a fair bit of extra stem so whilst it was still at 22.23mm diameter I parted off the spare to add to my come in handy drawer.


Having put that little extra bit in a safe place the stem was taken to diameter and the bolting flange turned:



Before going any further we need to think about drilling the bolting holes. If we wait until we have turned up the top of the pump we will have nothing solid to hold the casting by and we are likely to crush the bronze  if we try. So off to a mill and coordinate drill the holes (you could also use a rotary table )



We can now start to think about turning the top of the air pump so first boring it to depth  (1.6mm short of the length of the casting). Then opening the centre up to give the top of the pump chamber:



Before completing the inside it is time to do the outside, so first turn to diameter then set up the top beading using a parting off tool.



The outside follows a 7.5 degree angle which must run up to the centre of the top beading. The use of marker pen provides an easy indication of where the angle has progressed to:



Once it meets the top bead it is time to change to a more suitable tool and cut the 0.8mm deep part between the two beads Then using a 1.6mm diameter external cutter the beading was touched up:



The trickier bit was cutting the internal angle past the top of the pump chamber:



This was achieved using a ground down broken milling cutter mounted in a offset square tool clamp:



Jo