Retlas

[Alyn Foundry]

Yes steel conrod with separate shells , fitted bolts on the big end with nuts and lock nuts at the top and cross drilled for wire/pins. Gudgeon pin cross drilled and in from each end for oiling to the bearing. Should be two bolts to stop the pin moving rather then end pads. There is a sq headed screw and locknut in the end of the little end which I think must be to stop the bearing rotating.

CI bearing caps with oil pockets, separate split bearings. Not studs but fitted bolts passed up from below close to bearing hole but not cutting into it. Straight split on the caps not the legs going down the side of the bearings. good radius on the insides of the bearings to clear fillet on crank and a decorative 1/4 circle concave cut to the outside edge

Air valve on top of cylinder

Hi Jason.

Nice to have the engineering drawings !!   

You must have the plan for the Spirit version ?

Kind regards, Graham.

[Chipmaster]

Hi Jason, I assume your source is the "for my eyes only" drawings. Can you tell me whether the gas and inlet valves on the Retlas are reversed and any info about the trigger mechanism. I see the bucket arrangement to catch oil for big end lubrication - does it catch oil dripping from a thin blade that curves beneath the timing side main bearing similar to the 0 type ?
Regards
Andy

[Jasonb]

I'll come back to you on the inlet block but being hot tube there are quite a few differences or are you going to do away with the spark plug

You can see the sight glass oiler in this etching, a tube that is cut at an oblique angle passes through teh main body casting and is bent downwards and the bucket picks up the drip on the end.

[Alyn Foundry]

Hi Andy.

I can answer the big end lubrication question.

First look at Jason's post here.  http://www.modelenginemaker.com/index.php/topic,5720.msg115745.html#msg115745

You will see a small Brass lubricator halfway up the yoke casting. This has a Copper tube coming through and bent downwards with the end formed to create an oil droplet. The big end carries a trough that almost touches the tube and pulls off the droplet. Hence very poor lubrication, hit and miss with more miss than hit !!

Kind regards, Graham.

Posts crossed, by gum Jason, your fast !!      That might be the lamp Oil version in that engraving, or Hot tube ignition Spirit engine.

[Chipmaster]

Thanks for the information chaps - Jason and Graham 
I'll make up the big end trough to catch oil droplets, I agree it's more miss than hit, my model Gardner 0 type big end bearing has survived using a similar method. However, I'll have to make arrangements to catch the oil that misses!
I'll keep the spark plug to get the engine going Jason and consider a hot tube later.

Andy

[Jasonb]

I'll have to make arrangements to catch the oil that misses!.

Andy

Thats what the tap is for at the bottom of the one in the pic above

[Chipmaster]

Yes the tap releases the oil from a sump but the Retlas base has no sump so it will require a tray fitted to catch the surplus oil. 
Andy

[Chipmaster]

Making the connecting rod at the moment, Started with rectangular mild steel bar 16mm thick milled down to 1.75" wide.
Here is the original plan for the Retlas con rod.
207 Retlas Con-rod by Andy, on Flickr

I have decided to make an all steel con rod with phosphor bronze big end shells which will look like the Gardner Vertical engine and save the cost of a large piece of bronze.

Having marked out the steel bar the first job was to drill and tap two deep 1/4" Whitworth holes in the end, these holes will eventually house plain big end bolts. The end cap is 3/4" deep so I drilled the holes out to !/4" to a depth of 3/4". Centre holes were also drilled in to each end at this stage.

The steel bar was held in a quick change tool holder and lined up with the axis of the lathe. Then, using a large slitting saw the big end cap was sawn off, very slowly with the finest cross feed and a constant trickle of suds oil,  this ensured a square cut with a good finish.
Building Retlas 510 by Andy, on Flickr
Building Retlas 511 by Andy, on Flickr

I couldn't bore the big and little ends of the connecting rod on the face plate of my Colchester Chipmaster, it was too long so the next best method to achieve parallel bores was to use my milling machine. I decided to open out the big end to 7/8" od  for the 5/8" crank pin. I think the extra thickness will help the solder hold when I'm making the bronze split bearing shells.

Little end
Building Retlas 514 by Andy, on Flickr

Big end
Building Retlas 517 by Andy, on Flickr
3/4" drill
Building Retlas 518 by Andy, on Flickr
Boring head to take it out to just under 7/8"
Building Retlas 520 by Andy, on Flickr
An old 7/8" reamer
Building Retlas 523 by Andy, on Flickr
Profiling the connecting rod
Building Retlas 529 by Andy, on Flickr
A long way to go but much easier than using a hacksaw.
Building Retlas 533 by Andy, on Flickr

When I've done the other side I will transfer the connecting rod to my lathe for turning between centres.

Andy

[Ian S C]

I don't know if it's relevant, or the right way, but it's my way for con rods: as above for the start, but before cutting the cap off, I bore the big end to take the bronze for the bush which is drilled under size, and push it in, then cut though the con rod, and bush, and put  the bolts in the cap, bore/ream the bush to size.  No need for Loctite to hold the bush, and it can't rotate.  Don't know if that would be any use, the largest I'v done that way is 10 mm crank pin size on a hot air engine.
Ian S C

[Chipmaster]

Hi Ian, I think it's 'horses for courses'. Your approach - boring before cutting, might result in an elliptical hole that the machine reamer (in my  case 7/8" in steel) may have difficulty picking up and getting off to a good start. The thickness of the saw or side & face mill you use to cut off the end cap will determine how out of round the hole will be and suitable for reaming.
I find cutting off the big end cap first helps to ensure that I position the bore of the bearing so that the split bisects the bearing dead centre. Are you using your approach specifically for making aluminium con rods for hot air engines?
Regards
Andy

[Jasonb]

It does depend on the engine, in this case Ian's way is more like the full size gardner which has a gap between the rod and cap so by doing the hole first and then cutting the saw kerf leaves that gap. But put a finished bearing into the rod.

Other engines suggest putting shims between the two halfs so that they can be removed at a later date if you need to take up bearing wear. Others you have the two parts butted up tight and would either need to make a new bearing or skim the face of teh cap to take up wear.

Bearing rotation can always be countered by having a pin set into the rod and a matching hole in teh bearing which is quite common on full size or use the oiler to stop it rotating. White metal is another option as that won't rotate.

[Alyn Foundry]

Hi Andy.

Some nice photos, looking good.

I thought you might like to see the oldest ( so far ) Gardner in preservation. Size 2 ( 2 BHP ) Engine number 241 of 1896.

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

Kind regards, Graham.

[Chipmaster]

Good afternoon Graham, excellent, lovely sound, I presume the engine is at the Anson museum?
Must get back to watching the rugby match on tv now.
Andy

[Myrickman]

Graham, what an elegant little engine. The gas governer is mesmerizing. Like the horsepower measuring apparatus also. Thanks for posting

[Chipmaster]

Milling the other side of the connecting rod.
Building Retlas 534 by Andy, on Flickr
Building Retlas 535 by Andy, on Flickr
Building Retlas 536 by Andy, on Flickr

On to the lathe for turning between centres. I could have put a bolt through the eye of the big end to drive it but it seemed safer with the improvised two bar 'carrier' clamped over the split line of the big end in case any mishaps put a strain on the assembly.
Building Retlas 537 by Andy, on Flickr
Building Retlas 538 by Andy, on Flickr
Building Retlas 539 by Andy, on Flickr

The lathe's taper turning attachment is being used to machine the rectangular section of the rod and produce a fine taper.
I'll take it slowly because I have found the results produced by my taper turning attachment rather variable  . The attachment looks to be in good condition and is well lubricated so perhaps a worn cross slide feed screw is to blame? I would be interested to hear of other members experiences with taper turning attachments.
Andy