D.Maggs - workshop engine

[redhouseluv]

That's very kind of you I've been working on a drawing of my own using the original strap and creating an inner with the correct throw, but its a bit Heath Robinson tbh.

Have emailed you, thanks....

[Jasonb]

The reduced throw eccentric would be one option, probably with a bit of rotary table work to hollow it out for looks.

Or if the pump body was drilled out as shown in pink, then saw off the flange along the green line. You can then turn up an extension piece in red with spigots at each end to locate in the drilled holes and silver solder it back together. Then just treat as a new casting that will accommodate a longer throw (and smaller dia) ram

[redhouseluv]

I like it, a simple and different solution 

That way I keep the original eccentric strap and sheave (which I think look great) and the only mods are on the new casting and making a reduce diameter ram.

Thanks, I'll give it a go 

[Jasonb]

Unless you could be tempted to practice your silver soldering skills a bit more and make one that mounts low down so it is nice and rigid and has the ram cavity angled up towards the crankshaft ctr line?

[redhouseluv]

 I was wondering about fixing it and one thought I had was when I cut the flange off with the fixing arm, was to rotate it 180 degs before reattaching it so it would be positioned like the red rectangle therefore easier to fix to the base as its on the correct side.

I see what you are suggesting, which is soldering a bracket to the upright section. I have seen both variants (see pic), but the trouble with mine is the eccentric is outside the bearing block

[Michael S.]

Unfortunately, I can't give you a finished blueprint, but maybe a few suggestions.
The pump from the Stuart 9 would be perfect in terms of design. With a few pieces of brass or bronze and brazing solder, you could make something. It would fit the eccentric hub perfectly.

Best regards, Michael

[redhouseluv]

Here's the feed pump from the Stuart no.9 I made a few years ago -  In your second picture the air reservoir is very much along the lines I'm thinking of.

I've started to clean the flashing from the pump body casting and I think I'll proceed with it using a basic design, extending the body - I've just looked at how much Stuart's charge for a new set - eye watering!!!! I got mine at a fraction of the price from eBay and don't want to mess it up and I think if I can make work using the original eccentric and machine a bulbous air reservoir I'll be happy   

[redhouseluv]

I'm trying to calculate the extra length I'll need

The Stuart eccentric has a throw of 5/16" which means it moves 5/8" total
The Maggs eccentric has a throw of 5/8" which means it moves 1.25" total

Therefore I need 1.25" - 0.625" = 0.625" extra, but allowing for some wiggle room, 0.650"?

[Jasonb]

You could probably fiddle things so that the pump does not need extending so much. Keep the flanges as thick as possible and carry the ram hole a bit deeper into the casting* those together would total maybe 0.150 so only need to add 0.5"

* a small flat on teh ram may be needed so it does not cover the side hole.

[redhouseluv]

Thanks Jason, I've had to trim bits 'n' pieces off this morning just to get some parallel and perpendicular sides and surfaces, but nothing too significant so will allow an extra 0.050"

Lot's of filing and emery work but now I can start on machining the extension piece. I'm making the spigots 0.625" which will fit into a 1" diameter section so I shouldn't have to reduce the ram tube and ram diameter too significantly, maybe from 0.5" to 0.45"?

[Jasonb]

I would think 3/8" dia for the ram would be OK. That would still see it able to pump slightly more than the original Stuart then you can just use a piece of 3/8" Stainless rod

[uuu]

It still feels oversize to me - gut feeling.  My steam loco has a pump with a 1/2" bore and 3/4" stroke.    That's only a little bit bigger (6%?) than yours - but it handles two cylinders of 1.5" bore and 2.75" stroke - pulling a load of adults round a track.

Wilf

[Jasonb]

Out of interest what sort of rpm would the loco be doing?

The 5A was good for 1000rpm when working so certainly got through a reasonable amount of steam.

A mill engine with it's longer stroke is unlikely to be run at these speeds so could have a smaller pump, maybe drop it down to a 5/16" ram

[redhouseluv]

It still feels oversize to me - gut feeling.  My steam loco has a pump with a 1/2" bore and 3/4" stroke.    That's only a little bit bigger (6%?) than yours - but it handles two cylinders of 1.5" bore and 2.75" stroke - pulling a load of adults round a track.

Wilf

It may well be Wilf - it's a cosmetic addition and will never be used in anger, but has to look in scale with the rest of the engine which is quite a size hence the use of the Stuart 5a feed pump. The valve rod is 5/16" so yes, as Jason states, it may be an idea to bring the ram down to that size so it matches

Made steady progress today and made the hole for the extension spigot, next operation is to cut the flange with connecting arm off, job for another day ............

[uuu]

Out of interest what sort of rpm would the loco be doing?

The 5A was good for 1000rpm when working so certainly got through a reasonable amount of steam....

At 1000 rpm, the loco would be doing 15 miles per hour.  Half that feels fast.

The pump runs faster or slower to suit, of course.  But the loco has a proper load, so is using a lot of steam.  So will a full size stationary engine of course, but the model may just be idling.  Of course it has to look right - so you may have to organise a bypass (as the loco has), so you can pass excess feedwater back to the tank.

I see you have a traction engine avatar.  That could be a better comparison, as traction engines are often set idling for display.

Wilf