Twin Grasshoppers

[Michael S.]

Hello Andy,
you mean warped like this spring washer in the picture below?
This is of course more difficult to eliminate.
I have found that when I silver solder parts out of brass or bronze and the part is soft afterwards it bends well.
Maybe glow first and then apply targeted pressure. It then no longer springs back.
It's just an idea from me now.

Michael

[ettingtonliam]

Maybe grip the rim in the outside jaws of the chuck, insert a long close fitting bar into the hub and gently tweek til the bar runs true?

[Chipmaster]

Thanks for your thoughts about the flywheels Richard and Michael - yes they are warped like your spring washer.

After much fiddling with the valve timing I had the engines running together this afternoon. The flywheels, eccentrics and valve lever cranks are all secured with grub screws which is clearly inadequate as they have slipped several times but at this stage it makes adjustment slightly easier. I'm finding setting the timing difficult, impossible to achieve smooth running which might be due to the flywheels not being large enough. It might improve the running if I separated the engines by sawing through the crankshaft then couple them back together with the cranks at 90 instead of 180 degrees apart as they are. My Stuart Twin Victoria runs very smoothly with cranks at 90 degrees and it's self starting.

Here's a three minute video of it on YouTube,
<a href="https://www.youtube.com/watch?v=Hw60z9Rkvp4" target="_blank">http://www.youtube.com/watch?v=Hw60z9Rkvp4</a>

or Flickr
Running on both cylinders by Andy, on Flickr

Cheers
Andy

[crueby]

Yes - having the cranks at 90 degrees would mean it should self start, would always be at least one of the two pistons away from the top/bottom dead center position. That would be a more typical setup.

[Kim]

Beautiful!  Very fun video seeing your twin grasshopper run! 

Kim

[Dave Otto]

Very nice!

Dave

[john mills]

Nice to see them running
John

[Admiral_dk]

Happy for you, to see it run so well 

Per

[Chipmaster]

Steaming Grasshoppers, May 24th at the regular Wednesday steam engine meeting with my friend John.

YouTube video
<a href="https://www.youtube.com/watch?v=ZvmHHdt6yVU" target="_blank">http://www.youtube.com/watch?v=ZvmHHdt6yVU</a>

the same video on Flickr
Steaming Grasshoppers by Andy, on Flickr

The engine was very difficult to start because it kept locking up hydraulically with condensate. This is due to the large cylinder castings, inadequate cylinder drain cocks and the long steam pipe. It took about five minutes to get the engine running and as the gland packing settled down leaks developed on a grand scale. Anyway the engine provided some messy and quirky entertainment, we haven't seen another engine like this.

We also ran my Allman engine with some new gas pipe fittings, it ran very smoothly without needing to be clamped to the bench.

<a href="https://www.youtube.com/watch?v=NkCaKk60Frg" target="_blank">http://www.youtube.com/watch?v=NkCaKk60Frg</a>


The epilogue
When I cleaned the engine I found one of the crankpins was loose between the crank webs. I had always wondered how the crankshaft was made and this suggests it was pressed together and couldn’t take the strain of two 1.9/16" cylinders probably out of sync. I’ll have to make two new crankshafts that will be silver soldered together.

Andy

[Admiral_dk]

Wonderfull steady beat to the Allman 

Hope you get the rest of the double fixed to your satisfaction 

Per

[Chipmaster]

Broken crank - pictures of the crankpin that came apart.

Twin Grasshopper Steam Engine Build by Andy, on Flickr

Twin Grasshopper Steam Engine Build by Andy, on Flickr

The shaft is 1/2" diameter but I had to phone several suppliers to find someone with 1/2" precision ground mild steel in stock, I hope that doesn't portend imperial pgms supply problems. I might be able to use the existing crank webs on the replacement  crankshafts.

A picture of the surviving grasshopper.

Twin Grasshopper Steam Engine Build by Andy, on Flickr

Andy

[SteamR]

Steaming Grasshoppers, May 24th at the regular Wednesday steam engine meeting with my friend John.

YouTube video
<a href="https://www.youtube.com/watch?v=ZvmHHdt6yVU" target="_blank">http://www.youtube.com/watch?v=ZvmHHdt6yVU</a>

The epilogue
When I cleaned the engine I found one of the crankpins was loose between the crank webs. I had always wondered how the crankshaft was made and this suggests it was pressed together and couldn’t take the strain of two 1.9/16" cylinders probably out of sync. I’ll have to make two new crankshafts that will be silver soldered together.

Andy

Hello Andy,
this is a nice configuration with the twin arrangement. I like the motion.
You can now arrange the new crankshaft in 90° arrangement to improve starting procedure.

Richard

[Chipmaster]

What happened after the crankshaft fell apart six months ago......

I was tempted to leave it as a single Grasshopper which would have been practical given the weight and bulk of the pair. They also need more steam than my Stuart 504 can provide, I have a larger boiler but combined they're a pain to set up.

Twin Grasshopper Steam Engine Build by Andy, on Flickr

However, I decided to make two separate crankshafts with a coupling between the engines that would be easy to separate and to have them 90 degrees out of phase for self starting. I also reduced the stroke by 1/8" to keep the pistons well away from the end covers, I had difficulty setting up the engines and this would make life easier.

Nothing unusual to write about making the two crankshafts so here are some pictures taken along the way.

Twin Grasshopper Steam Engine Build by Andy, on Flickr

Twin Grasshopper Steam Engine Build by Andy, on Flickr

Twin Grasshopper Steam Engine Build by Andy, on Flickr

Twin Grasshopper Steam Engine Build by Andy, on Flickr

Twin Grasshopper Steam Engine Build by Andy, on Flickr

Excess ends sawn off the webs and crankshafts loosely assembled prior to silver soldering.

Twin Grasshopper Steam Engine Build by Andy, on Flickr

Silver soldering - Flickr video

Twin Grasshopper Steam Engine Build by Andy, on Flickr

Test fit for one of the crankshafts.

Twin Grasshopper Steam Engine Build by Andy, on Flickr

Test fit for one of the crankshafts - feather key in flywheel unlike the original that relied on a grubscrew

Twin Grasshopper Steam Engine Build by Andy, on Flickr

I then made a four pin coupling connecting the two 'Twin' engines. Temporary 4BA screws in this picture.

Twin Grasshopper Steam Engine Build by Andy, on Flickr

Flickr video

Twin Grasshopper Steam Engine Build by Andy, on Flickr

Con rods fitted.

Twin Grasshopper Steam Engine Build by Andy, on Flickr

Coupling disengaged so that the 'bronze engine' can be tested.

Twin Grasshopper Steam Engine Build by Andy, on Flickr

Coupling disengaged so that the 'brass engine' can be tested.

Twin Grasshopper Steam Engine Build by Andy, on Flickr

Coming Soon - some videos edited to show the engines working together 

Andy

[Admiral_dk]

Interesting concept - might even have been found in the full size world back then 

Good to see that you resque this build 

Per     

[Chipmaster]

Cheers Per,

Some YouTube videos.

First two show the engine(s) running on compressed air,

<a href="https://www.youtube.com/watch?v=2WOgFfgeKZs" target="_blank">http://www.youtube.com/watch?v=2WOgFfgeKZs</a>

<a href="https://www.youtube.com/watch?v=i768_StkeyQ" target="_blank">http://www.youtube.com/watch?v=i768_StkeyQ</a>

Running on steam, very messy.

<a href="https://www.youtube.com/watch?v=UPrFC5Bfhqw" target="_blank">http://www.youtube.com/watch?v=UPrFC5Bfhqw</a>

Just one running on steam

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

Andy