LE CRAB

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Bill Shields
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LE CRAB

Post by Bill Shields »

Anybody out there specifically have a LE Crab?

Have a question regarding hou the cylinder exhaust is handled?
Too many things going on to bother listing them.
hoppercar
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Re: LE CRAB

Post by hoppercar »

Yes....what do you want to know
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Bill Shields
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Re: LE CRAB

Post by Bill Shields »

Hi.

Fellow at local club has one but has trouble keeping up steam on propane, which appears to be setup reasonably, and I am doing a little comparison to others.

#1-> fuel you use and does it steam well?

#2 -> is the exhaust from the cylinders piped up into the stack?

#3 - what is the inside diameter of the stack?

Any suggestions if you may have had similar experience.. boiler not keeping up with demand
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hoppercar
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Re: LE CRAB

Post by hoppercar »

Mine burns coal...always popping off.....yes, exhaust is piped up the stack...stack dia. About 1 1/2 inches...never had any trouble keeping up steam.....
Santafescotty60
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Re: LE CRAB

Post by Santafescotty60 »

whose burners are you using? what pressure is the burner set at? does the regulator have adjustment and gauge or is it a barbeque regulator. which will not work if reg is stuck what color is flame? Scotty
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Bill Shields
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Re: LE CRAB

Post by Bill Shields »

Thanks for the thought.

I have a lot of experience with propane burners.

In this case it does not immediately appear to be a burner related problem, which is why I am asking about other parameters for this particular loco design.

If someone out there can provide the actual stack ID of a successful, running loco, it would be appreciated.

Obviously (or maybe not, so I apologize), I am thinking that the existing stack, which is not the original, may be mis-sized.
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SPSteam2491
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Re: LE CRAB

Post by SPSteam2491 »

I have a 1½" scale Tom Thumb that has a vertical boiler and likely a similar setup to the Crab. It primarily runs on coal but I converted it in 2018 to run on propane during the Triennial at Train Mountain.

When running coal, there is a baffle plate on top of the tubes to length the path of the cinders and helps prevent most of them from going directly out the stack. The engine can be run without this baffle on coal with a minimal change in performance. The baffle plate is located above the tubes by ~3/4" and just below the exhaust ring.

When running on propane, this baffle plate is 100% needed to decrease the draft on the fire. I used a round propane burner used for cooking beer (see the link below) and during testing without the baffle, could easily make pressure when steaming up. As soon as you start going out onto the track, you could watch the pressure drop as the exhaust from the cylinders would pull the flames into the tubes and extinguish the flames before complete combustion and also cooled the engine off. Once I added the baffle plate back in, I could hold pressure at 5psi of propane and was able to make it up the serpentine at Train Mountain with 4 cars holding 80psi or more or steam.

If I had more time, I think I could have made the baffle plate larger to restrict the flow of gasses further to allow the burner to operate at lower pressures.

Link for Propane Burner https://www.psychobrew.com/product/b100p/
Thanks
John LaFavor
Pacific Design Shops
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Bill Shields
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Re: LE CRAB

Post by Bill Shields »

you are along my line of thinking....

the burner setup appears to be sufficient from my experience

only on this particular loco, the steam exhaust is dumped out on the ground and does not go up the stack....but I am still thinking that a lot of the heat is going right out what I believe is an oversized (non original) stack.

I have no idea if it was designed this way, i just know that it does not appear to work.

rather than plunk around with a baffle, i am considering choking down the 2" diameter stack a bit.

yes, the guy has put turbolaters (spelling wrong -> but sure you know what I mean) in the tubes and says that they did not change anything (which I am scratching my head about)....

know the stack diameter on your TT?
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SPSteam2491
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Re: LE CRAB

Post by SPSteam2491 »

I can take some measurement and pictures of the engine later today. From what you described, it sounds like the engine has a very unique setup.
Thanks
John LaFavor
Pacific Design Shops
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Bill Shields
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Re: LE CRAB

Post by Bill Shields »

Just the stack ID is all I really need at this time, thanks.

Going to go with my gut experience for the rest of it.

I am not interested in tearing this loco apart...I am just looking to improve things in an expeditious manner..and going to start with a drop in orifice in the stack.
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SPSteam2491
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Re: LE CRAB

Post by SPSteam2491 »

No problem, my stack ID is 2.25".
Thanks
John LaFavor
Pacific Design Shops
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Bill Shields
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Re: LE CRAB

Post by Bill Shields »

👍
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