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[muleears]

A week or so ago I began preparing the Alexandra (which is equipped with a Krick twin engine) I noticed that these screws (highlighted in the pic, the two shown and two corresponding on the other side) were not tight. Being absolutely sure they should be, I tightened them down.  Yesterday I placed the Alexandra in the tub for some "sea trials" since I had never had the boat in the water before (or any steam powered boat for that matter). To my dismay it wouldn't run!  It would turn over one or to revs and that was it.  I could find nothing binding and there appeared to be enough steam.  Long story short, I realized I may have adjusted something I shouldn't have by tightening those screws. So I loosened them and viola! She runs again!  My question is, what do these 4 screws do? I assumed they just held the top plate on, but they are spring mounted so I guess there is more to what they do.  Can anyone fill me in and explain just how tight or loose, they should be?

[derekwarner]

Cal....all bolted construction joints should be secure............in this model engineering case [approx 3 mm diameter ?]  nipped up  .....if this minimal torque creates a binding effect within the engine....... then this is an indication of an alignment issue within the structure of the engine ....... ie., between the 4 columns & the top plate of the engine.......Derek

[warspite]

Looks like vibration loosened the screws and then misalignment has taken effect, when you tighten them back up the engine wont work because the parts are not back in their original places, just needs carefull setting.

[hammer]

That's spot on Derek. RGY

[muleears]

Thank you gentlemen all for your assistance.  One thing I should have pointed out.  This top plate that the screws hold down is spring loaded. Underneath the plate and around each screw is a spring.  Difficult to see in the pic but I think you get the idea.  It appears the top plate floats on these springs.  When tightened down (spring compressed completely) engine won't run. When the screws are backed off two turns or so, so the plate has some slight movement the engine runs.  Why would these be here if it were simply supposed to be screwed down tight?

[warspite]

This is the systems anti vibration dampers, allowing the top plate to move as intended. there may be another moving part connected that need to move due to its small scale.

[muleears]

Thanks Warsprite, that makes sense.      For the time being I have them loosened about two turns and just had a successful 15 minute "sail" in my garden tub!

[Tug-Kenny RIP]

I'll start by saying that I know nothing about steam engines so I am viewing this problem from a machine perspective.

As it has spring tension on the screws, would it be wise to apply some gentle locktight when the satisfactory running position was found  ??

Cheers

Ken

[muleears]

Thanks for the good advice Ken. I REALLY know nothing about steam engines (obviously).  I guess my only question now is how do I know when a satisfactory setting is found? I suppose where the highest RPM is reached? Or where it will run the slowest (if not one in the same)?

[warspite]

Not being an experienced steam engineer, I guess the two reciprocating pistons being fitted to the plate will fight each other as they rotate the rotary crankshaft fitted to the base board, these springs are compensating for this intolerance and fully tightened up screws are compressing the connecting rods, therefore in-effect clamping the arrangement like a vice.
 
Each piston has a maximum stroke length, if the shortened connecting rod stroke, pushes down and cannot extend past its return point then it stops, as the screw is released the stroke length starts to approach this ideal length and the connecting rod passes the return point and the piston then continues up pushed by the other pistons travel downwards, unless this too has a shortened stroke, again releasing the screws on this side has the same effect. Ideally both of the connecting rods should be exerting the same pressure against the crankshaft as it is being pushed into the bearings that support it as this presure is released then the shaft should rotate more freely, reducing wear on the shaft faces and the bearings, too loose and the whole arrangement may start to exhibit vibration and things may fall apart, trial and error is needed to get the balance just right - the goldilocks effect    

[derekwarner]

mmmmmmmmmmmm  ...they are only slotted head screws....so the amount of induced torque will not be great...
If they were originally Loctited or fully tensioned [compressed spring washers] they should not have loosened
Just to be sure.......why not post a question to the manufacturer Mr Krick........ Derek

[SailorGreg]

Cal - have you tried adjusting the screws with the engine running?  Careful, small adjustments up and down might allow you to see how varying the tension in the springs affects the running of the engine.  I would guess that there is a sweet spot where RPM and power reach a peak.  You can then test how slowly the engine will run to see if the setting works across the range.  I would assume that is where the screws should be set.

Have fun with the steaming 

Greg

[steamboatmodel]

The Krick engine looks to be assembled from Wilesco parts, and this looks like a quick and cheap way to make things work.
Regards,
Gerald.

[muleears]

Cal - have you tried adjusting the screws with the engine running?  Careful, small adjustments up and down might allow you to see how varying the tension in the springs affects the running of the engine.  I would guess that there is a sweet spot where RPM and power reach a peak.  You can then test how slowly the engine will run to see if the setting works across the range.  I would assume that is where the screws should be set.

Have fun with the steaming 

Greg

I have Greg and I think I have found the spot.  I do plan to have fun. One week from tomorrow the Alexandra will make her maiden voyage.  Under my Captaincy anyway!

[AlexC]

 
 
The top mounting plate is known as an entablature which carries the cylinders, valve chests and throttle/reversing mechanism.
 
This should be rigidly fixed in relation to the crankshaft... i.e. screwed firmly to the top of the 4 columns... if it is not, then it will play havoc with piston rod to con-rod alignment, cylinder to crankshaft alignment eccentric rod to piston valve alignment and valve timing events... all of which are critical.
 
It would seem that the columns, in this case, are TOO SHORT, and i suspect that when your bolts are fully tightened the piston is hitting the top of the cylinder... making it a non runner.
By loosening the bolts, the springs effectively increase the column length by a small amount, thus giving clearance for the piston at the top of its stroke.
 
This movement will also affect the piston valve timing (steam valve) as this is also derived from an eccentric on the crankshaft.
 
I would suggest that you replace the springs with a suitable number of washers to achieve the required clearance and then screw the entablature down firmly... this will result in a much steadier running... with the entablature bouncing around on springs you are inviting severe damage to your pistons, cylinders, con-rods, piston valves and linkage and the crankshaft.
 
I cannot believe that a manufacturer of steam engines would have ever considered producing an engine built this way... are you sure it is an original?... it looks more like someone has cobbled together a twin out of a couple of single cylinder engines and mis-calculated the required column length.
 
Hope you can get it sorted out properly.
 
Best Regards.
 
AlexC

[muleears]

Alex,
If I screw them down tight the engine will still turn over, but it will not run on steam.  The idea of replacing the springs with washers sounds to be a good one.  The springs are quite stiff so I doubt there is much play, but I'm sure there is some.   I have been told by others here that this is a older Krick that came with the Alexandra but was manufactured by Wilesco.  I have  a new Stuart Puffin but it is too late to try to install that before my trip next week. I will have to make do with the Krick.  I cannot answer why it was built this way but it appears to be all of factory manufacture.  I see no evidence of fabrication (to my untrained eyes anyway), that would lead me to believe it is a Frankenstein!

[pettyofficernick]

Hi Cal, I too would go with replacing the springs with shim washers, just don't sound right having the cylinders 'floating' like that, a bit of experimentation with shims and once you have found the optimum height of the columns, secure with a drop of threadlock.........

[AlexC]

Hi Muleears,
 

 If I screw them down tight the engine will still turn over, but it will not run on steam

.
 
If the engine turns over ok with the screws tightened down then your problem is almost certainly the steam valve timing.
Tightening the screws will lower the entablature plate a little and this will have the effect of raising the steam piston valve in relation to the cylinder. This will create a valve timing issue.
Your engine is fitted with PISTON VALVES for steam inlet and exhaust and the total travel will only be around 3/32" - 1/8" either way... the small amount of movement created by tightening the entabulature screws will thus be a large percentage of this movement and is probably not allowing one of the cylinder steam ports to open at the correct place/time relative to the crankshaft position.
 
With the screws fully tightened there are two possible solutions for this; -
 
1/ Adjust the length of the eccentric rod/s, if these are adjustable (possibly they will be threaded into the bottom of the piston valve, with a locknut, and will need to be screwed IN about 1/2 - 1 turn)... trial and error.
 
2/ OR... Rotate the engine until one of the pistons is at TOP DEAD CENTRE (take note of the direction you turned the engine). Slacken the grubscrew/s holding the ECCENTRIC to the crankshaft and adjust the position of the eccentric (turn it slightly in the same direction as the engine rotation, whilst keeping the piston at TDC) and re-tighten the grub screw/s.
 
You will need to perform the adjustment (by the same amount) on both cylinders, always turning the engine in the same direction.
 
Perhaps you can find someone at your sailing meeting, with an understanding of steam engine adjustments, who can assist you.
 
In the meantime... replace the springs with washers and enjoy your sailing session.
 
Best regards.
 
AlexC