"Catherine", a USA "Sweet Pea" engine build

[Benjamin Maggi]

Ben, you said the classes proved to be very useless.

PM sent. I don't want to post my comments in public or derail the thread.

[h2ogasnz]

Hi,

Great to see another Sweet William being built, at the speed you're working you will pass me in no time! I haven't made any progress on mine one in the last couple of months due to all the normal things getting in the way e.g. house painting, garden to look after and helping out with the baby...

Hope to get back in to mine this week coming

Jeffrey

[Benjamin Maggi]

I am not going fast... I only decided to post all my progress to date so it looks fast. I started last June. I get to my friend's house to work about once a week, usually on average 3 times a month. And, I do what I can at home. We are working on the axle boxes right now.

[Benjamin Maggi]

Work on the axle boxes continued. I planned on using needle bearings inside the axle boxes, with hardened "races" on the ends of the axles themselves. Sourcing what I wanted in the size I wanted proved more difficult then I thought, as McMaster Carr and MSC both had listed what I needed in their [older] catalogs, but now had them listed as discontinued. After a lot of phone calls around the country, I found them.

The axle boxes were already drilled with a 7/8" bit, so to get them ready we then opened up the hole with a 1.25" bit. I am not familiar with such large bits and it was both interesting and intimidating to use. A proper feed rate and some cutting fluid were the key. This hole went all the way through the axle box.

Having been chucked so that the "inner" faces of the axle boxes were the ones being machined, we then bored the hole up to 1.5" diameter almost all of the way through. This dimension allowed for a press-fit of the needle bearings into the axle boxes, and they cannot fall out because the bore doesn't pass all the way through. The needle bearings have an oil hole in them and I considered drilling a top-feed oil hole in the axle box and trying to match them up but figured it was a bad idea. More likely then not, water or grit would get washed down into the needle bearing, which surely is a bad thing.

The needle bearings fit into the axle box and are slightly recessed in, so gentle pressure with a benchtop vice alone wasn't enough. A short round piece of steel used as a "spacer" allowed us to get the bearing in the rest of the way. Then the spacer was removed.

To prevent grit or chips from getting into the bearings, I covered both openings with blue painters tape for now. I need to work on finishing the horn-keeps next.

[SilverSanJuan]

How will you oil the needle bearings? Or, will you just grease them?

That is a BIG intimidating drill bit, isn't it.

[Benjamin Maggi]

The bearings come oiled or greased, I am not sure. The needles themselves are "double sealed" on the edges, but I have seen rubber-like rungs that slide over shafts to further protect the bearings from outside dirt. I suppose I will just stuff them with grease when I install them on the axles.

[prlawiii]

The bearings come oiled or greased, I am not sure. The needles themselves are "double sealed" on the edges, but I have seen rubber-like rungs that slide over shafts to further protect the bearings from outside dirt. I suppose I will just stuff them with grease when I install them on the axles.

Ben,

The Allen Mogul plans provide for an oil hole drilled into the end of the axle, with a hole from the outside of the axle drilled to intersect this in the area that will be in the bearing when the axle is installed. The hole on the end of the axle can be tapped for one of the spring loaded oil caps (similar to a grease fitting) to keep out dirt. Oil squirted into the end of the axle will make its way into the bearing.

Herman

[Benjamin Maggi]

Interesting idea. I have seen other threads on this board discussing "hollow axles" for just this purpose. I own a set of the Mogul plans, so it is worth looking at.

[Benjamin Maggi]

Though we had the axle stock in hand, we pressed on with the eccentrics and straps. As I was trying to avoid purchasing castings from overseas, I contacted Allen Models of Michigan to see if any of their Allen castings would work. Sure enough, their straps were nearly what I needed so a pair were ordered.

The engine has outside Hackworth valve gear, but it features two axle driven water pumps. So, everything has to be done in pairs. The straps themselves appear to be brass, and though it machined well enough it was somewhat "sticky." Care had to be taken when turning it on the lathe, and milling away portions for the bolts was also done gently.

[Benjamin Maggi]

The eccentrics themselves were turned from some C12L14 leaded steel that we had on hand. It was held between the lathe chuck and a free spinning live center. Using a thin profile cutter worked well enough but there was a bit of chatter which coolant didn't seem to fix. So, we tried making a new cutter that was wider (but not too wide- the slot is only 5/16" wide and 1/8" deep) and that worked better. However, the finish in the slot wasn't good.

So, we then used files while running the lathe to clean it all up. This, as well as some judicious filing on the straps to thin them slightly allowed everything to come together perfectly without any bind. I hope that the eccentric straps don't wear and jam too much, as they are being used to deliver water to the boiler. However, as the underside of the engine is pretty empty and access isn't all that difficult if I need to replace them after a couple of seasons it won't be the end of the world

[steamin10]

Welcome to machining brass. If by meaning 'sticky' it has a tendency to draw the tool in, or suck on the drill, you get the same as I do.

Scraping with a dull tool or less relief can remove the surprises. For really fine work, tighten the ways and make the tool razor sharp, with small but deliberate infeeds for fine chips. If you hog, your done.

It is what I do.

[Harold_V]

When issues with hogging (self feeding) are present, reducing rake is the recommended procedure.

Free machining brass (or bronze) will respond perfectly well to little or no positive rake. If some rake is desirable, balance the ability to hog with limited relief. Between those two features, you should be able to machine such materials with success, even on a loose machine.

Harold