Author Topic: Benson inverted steam engine (Read 5347 times)

gbritnell · « **on:** April 29, 2021, 11:12:03 PM »

Gentlemen, I've had this engine on the back burner for some time so I thought it was about time to get back to work on it. This is the Benson vertical steam engine. (some videos on Youtube) Not one to leave things alone I took the drawings and scaled them to .75 of the original. The flywheel is a little over 5.00 inches in diameter so with the cost of brass out of this world I decided to fabricate it. I started by cutting rectangular segments then cut the ends at 45 degrees. I made a fixture to hold all the pieces true and silver soldered them together. After cleaning up I turned the O.D., I.D. and faces leaving a little for later truing after assembly. I drilled for the spokes and made a hub with pin holes to locate the inner ends of the spokes. The spokes were turned with a taper leaving enough of a true diameter on the outside to allow them to slide out then back into the hub. This required a more elaborate setup for assembly. All the parts were cleaned and fluxed then soldered with Stay-Bright alloy solder. After assembly a bar was turned with a diameter that would fit the hub hole. This was threaded and the flywheel was mounted and trued up. The cylinder has a conical band replicating the original ornate casting so I turned that shape then made and fitted the steam chest to the cylinder. This was also soldered together. The base has a lot of steps and radii so the rotary table was used extensively. The top of the column has a rectangular shaped bracket that hold the crankshaft and this also was a fabrication. I will post more as the engine progresses.

RReid · « **Reply #1 on:** April 30, 2021, 12:28:19 AM »

Great looking parts. I especially like the look of the cylinder/steam chest assembly. I'll keep that approach to flywheel fabrication in mind for the future! Looking forward to what comes next.

crueby · « **Reply #2 on:** April 30, 2021, 12:53:40 AM »

Another George build, excellent!!

I've thought about making a flywheel like that but didn't think I'd get the joints good enough. Do you think it would be worth doing half lap joints and screwing the overlaps together for soldering rather than making a holding jig? Or would that be even harder to get good fitting joints?

I remember watching the wheelwrights at Williamsburg building wagon wheels the way you did, fascinating to see them go together.

Craig DeShong · « **Reply #3 on:** April 30, 2021, 01:57:20 AM »

I was wondering what George has been ‘up too’. Now we all know. Great start George, I’ll be following along.

Don1966 · « **Reply #4 on:** April 30, 2021, 04:58:23 AM »

Awwww George my friend you exceeded my expectations ……..did I say……..I……………likeeeeee……

Ps Are we going to polish it….?.

Don

Kim · « **Reply #5 on:** April 30, 2021, 05:51:40 AM »

Excellent! I'll be following along too, George.

Interesting way to make a flywheel. I've seen ship steering wheel's made that way, but never thought about a fly wheel!

Kim

AVTUR · « **Reply #6 on:** April 30, 2021, 12:16:12 PM »

George

Is this the Anthony Mount engine? I only ask since I am coming towards the end of making my Hick Crank Over engine and may get another set of castings to carve.

AVTUR

Chipmaster · « **Reply #7 on:** April 30, 2021, 12:17:04 PM »

Superb, wish I could achieve finishes like that.
Andy

kvom · « **Reply #8 on:** April 30, 2021, 03:00:28 PM »

3/4 size is quite challenging. I did the 1x size and it was a good challenge. Made me wish I'd followed Jason and done 2x.

Timing the engine was/is a challenge as the view into the steam chest is blocked by the cylinder.

Waiting to see how George does the gears for the governor.

Jasonb · « **Reply #9 on:** April 30, 2021, 03:42:44 PM »

Well I don't expect George will be buying in his gears

Mine was actually 1.5 times the original A.Mount drawings but 2 x would be impressive.

Though I was a bit disappointed when I saw the model as I was expecting to see a model of something else made by Bensons with an INVERTED arrangement not the true vertical that it is.

bent · « **Reply #10 on:** April 30, 2021, 07:34:22 PM »

Yup, I like the flywheel too, need to try a built-up one of these days.

gbritnell · « **Reply #11 on:** May 12, 2021, 05:53:11 PM »

Time for a Benson update. I have finished the parts for the throttle valve, cylinder cover, piston and rod, crankshaft and crank arm. The steel parts are all 303 stainless steel. When I get to the gears for the governor I'm going to see if I can increase the size of the crank gear to speed up the governor at least by 50%. This should make the throttle work better. All the videos I see of the full sized model show that at slow speeds the governor weights hardly move.

gbritnell · « **Reply #12 on:** May 12, 2021, 06:00:09 PM »

On this engine there is a support arm that attaches to the column and terminates with a bushing that supports the piston rod. Kind of like a crosshead of sorts. In the original drawings they have you fabricate it by silver soldering the plate and arm together. Rather than try to fiddle with soldering and alignment I opted to cut it from the solid. The concession being that I would make a bushing for the piston rod and soft solder it to the arm with everything in place. I made a step-off chart from the CAD drawing and created the profile of the arm. It was then cut free with the slitting saw.

gbritnell · « **Reply #13 on:** May 12, 2021, 06:02:49 PM »

I completed the eccentrics and straps along with the rods and clevis ends for the valve and water pump. I assembled all the parts to this point to get a peek on how it will look.

Roger B · « **Reply #14 on:** May 12, 2021, 06:30:51 PM »

Looking good (as ever)

crueby · « **Reply #15 on:** May 12, 2021, 06:42:42 PM »

Thing of beauty - looks like one of the old Victorian era scientific instruments, wonderful job!

Dave Otto · « **Reply #16 on:** May 12, 2021, 09:24:10 PM »

Very nice George!

Dave

gbritnell · « **Reply #17 on:** May 17, 2021, 04:08:00 PM »

The drawings call for a pair of identical size helical gears which means the governor runs a crank speed. The charm of these engines and most steam engines for that matter is their slow operational speed. I have looked at the Youtube videos of the Benson and even when the speed is increased the governor doesn't have much action so I decided to try and speed up the governor by making the ratio a little different than 1:1. Using the spreadsheets provided by Don I was able to keep plugging numbers in until I got something that would satisfy the center spacing. I started with the tooth count that seemed appropriate then kept changing the diametral pitch and adjusting the tooth count until I hit the center distance by .002. I ended up with a D.P. of 64, tooth counts of 17 on the crankshaft and 13 on the governor and a helical angle of 45 degrees.
With all the index plates I've made I didn't have one that would give me 17 and 13 spacing so I had to make a new one. Along with this was the need for 2 more helical templates. The thing with the helical templates is that they are pretty much throwaways unless you plan on making the same gears in the future. Each template is made for a specific P.D. and helical angle.

Admiral_dk · « **Reply #18 on:** May 17, 2021, 10:31:43 PM »

Nice gears and will be interesting to see if your plans for how well the governor will work after this mod - really hoping that you have success

Per

Craig DeShong · « **Reply #19 on:** May 18, 2021, 04:00:17 AM »

Quote from: gbritnell on May 17, 2021, 04:08:00 PM

With all the index plates I've made I didn't have one that would give me 17 and 13 spacing so I had to make a new one. Along with this was the need for 2 more helical templates. The thing with the helical templates is that they are pretty much throwaways unless you plan on making the same gears in the future. Each template is made for a specific P.D. and helical angle.

You’ve made many more helical gears than I, George; but I haven’t been able to reuse any of mine either

This engine has the classic styling I just Love.

gbritnell · « **Reply #20 on:** May 22, 2021, 03:12:29 PM »

I have the gears tapped for set screws and fitted and mounted in place. I finished the connecting link that goes from the piston rod crosshead to the crank arm. This was cut from a solid block. I gave myself the coordinates and stepped off the shape then cut it free with a slitting saw. The support arm from the column was made without the support bushing on the the end. I thought it might be too hard to hold all the dimensions exactly so once the arm was mounted to the column and the piston rod assembled I made the bushing and soldered it in place.

tvoght · « **Reply #21 on:** May 22, 2021, 03:22:24 PM »

It is really an attractive engine, George. I have been watching. --Tim

crueby · « **Reply #22 on:** May 22, 2021, 04:15:58 PM »

Beauty!

fumopuc · « **Reply #23 on:** May 22, 2021, 06:43:22 PM »

Hi George, very nice.
And as always sure very small.

Don1966 · « **Reply #24 on:** May 22, 2021, 06:43:38 PM »

Just beautiful work George you’ve out done my Benson. By increasing the speed of the governor will depend on which weight balls you use. I used brass balls on mine and the ratio was ok at max speed they sling out to full extension. Good luck my friend. Are we going to polish it…?.

Don

gbritnell · « **Reply #25 on:** May 22, 2021, 07:39:33 PM »

Thanks everyone. Don, your engine is beautiful! I don't think I'm going to buff it because there are just too many tiny pockets to try and get into. If it's half buffed it will look worse than just leaving cleaned up.
gbritnell

gbritnell · « **Reply #26 on:** May 23, 2021, 11:04:50 PM »

All of the governor pieces made. The links were cut square on the mill then very carefully the connecting shafts were turned, .050 diameter. All of the rectangular pads and the ends of the upper and lower brackets needed radii put on them. No other way than to carefully file and polish. The balls were stepped off in the lathe with a radius nosed cutter then filed and polished. The link bolts are all M1.2 x .25. I have to make nuts for all of them. In the last picture I held the governor open with a scale and you can see how small the parts are.

crueby · « **Reply #27 on:** May 23, 2021, 11:14:17 PM »

More wows. Have to order another box of Wows soon!

Chipmaster · « **Reply #28 on:** May 24, 2021, 09:49:35 AM »

Exceptional craftsmanship

Andy

RReid · « **Reply #29 on:** May 24, 2021, 02:42:45 PM »

Let me just add my compliments. Lovely guv'nor!

BobJohn · « **Reply #30 on:** July 09, 2021, 12:16:00 PM »

Very nice work, the brass is spectacular. The Benson is already a small engine, scaling it down has to be quite a challenge.

I've just started a Benson Vertical a few weeks ago. However, I've scaled it up X1.6. I'll use aluminum castings from my backyard foundry. It's proving to be a really fun project. I think speeding up the governor is a good idea, I'll try to do the same. I'm in the process of casting the entablature now, I may move the governor mounting hole to make it easier to add a different gear ratio.

I'd be interested in how the piston rod bracket/bushing part of the project goes. It looks like it could be an alignment challenge.

When I get a bit further along I'll share a few pictures.

Bob

gbritnell · « **Reply #31 on:** July 09, 2021, 08:13:09 PM »

Hi Bob,
I had the same concerns about the alignment of the piston rod support bracket so I made up the bracket without the bushing. I assembled the cylinder/piston/rod in place then soldered the bushing to the bracket. If you're making the whole thing out of aluminum you could maybe make the part of the bracket that extends from the column as one piece then make the arm the goes back to the centerline as another. You could then screw the 2 pieces together and file and adjust as needed for alignment.
gbritnell

BobJohn · « **Reply #32 on:** July 10, 2021, 03:42:40 PM »

Good tip, when I get that far I'll see if brass is an option.

I like cutting gears, but helical are a bit much for me. I've looked at SDP and they have a 48DP 20T and 35T that would would put the PD at .7365 and a speed up of 1.75:1. The current dimension on the entablature of the crankshaft and governor shaft is .712. Shouldn't be that much of a change to the pattern. Though I haven't check pricing.

Working on a pattern for the cylinder today. Hope to make it so I can use wood lagging. Should be able to attempt a casting next week some time. If successful, I'll have four parts. I'll post a couple pictures.

Bob

BobJohn · « **Reply #33 on:** July 19, 2021, 07:44:18 PM »

I have four parts now, so I figure I can include a picture or two. The engine will be 1.6 times the original.

gbritnell · « **Reply #34 on:** July 19, 2021, 08:09:09 PM »

Great looking castings! I'll be following along for sure.

BobJohn · « **Reply #35 on:** July 19, 2021, 09:33:26 PM »

Thanks George. Casting is great fun.

I thought I'd cast the pump body in brass. But, when I looked at the drawings, I had a hard time trying to figure what the plan would be for the pump intake. It looks like it just goes down into the base. Do you have any ideas for your engine?

The author said he added the pump so the engine would have work to do.

gbritnell · « **Reply #36 on:** July 20, 2021, 11:45:23 AM »

Being as I had no intention of using it I just made it like the drawing and it protrudes through the base.

Jasonb · « **Reply #37 on:** July 20, 2021, 01:01:22 PM »

Castings look Good

The layout of the pump as it is shown best suits decorative use where the outlet can pump through an open spout into a tank or barrel with a pipe from the bottom of the container back to the pump hidden in side a wooden plinth, the circulating water is just for show.

If you wanted to use it as a boiler feed pump then a bit of reconfiguring to allow for a side inlet that is above the cast base would be more practical.

I just built mine as a dummy and don't think I even added any gland packing or balls, all helps to reduce friction and get a nice slow running display model.

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Author Topic: Benson inverted steam engine (Read 5347 times)