quartering the eccentric crank

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cbrew
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quartering the eccentric crank

Post by cbrew »

Good Morning all,
I am making progress on the finial assembly of the baker geared ten wheeler..
I am looking for ideas for quartering the eccentric crank,, I know it needs to be 90 degrees from the crank pin,
I can probably do it by eye but we all know that it not going to be exact

Thanks
Chris
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srrl5
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Re: quartering the eccentric crank

Post by srrl5 »

I've not set up Baker, but I believe it should be the same as Walshart. You want to hold the input crank where when you move the forward-reverse lever the valve dose not move. Then measure the distance from the eccentric crank to the the input crank at both forward and reverse piston dead centers and adjust the position of the eccentric crank until the measurement is the same. That measurement is the correct length for the eccentric rod.

David Rohrer
We the willing, led by the unknowing, have been doing so much with so little for so long that we are now qualified to do anything with nothing.
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cbrew
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Re: quartering the eccentric crank

Post by cbrew »

Hi Dave,
I am focusing on quartering the crank its self. other then eye balling with a square

O
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kenrinc
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Re: quartering the eccentric crank

Post by kenrinc »

FWIW, it's my understanding that Baker gear is "inclined" by design therfore the return crank would not be exactly 90deg from the main pin. But I digress....

As for the quartering are you going to pin it? I've wrestled with this myself. I have my cranks slit, bolted and loctited to the pin. I couldn't figure out how to pull off keying them to the crank but if I find a good method I intend to do it. I'm not understanding how one can "mark" the crank and then remove it. Or maybe it's just drilled in place? In most of the literature I have, they locate the return crank then somehow mark and drill for a taper pin or an off center bolt that passes through the return crank and the side of the pin. For Walschaerts's the location process is a bit different so won't go into that.

Ken-
Last edited by kenrinc on Fri Dec 27, 2013 12:43 pm, edited 1 time in total.
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cbrew
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Re: quartering the eccentric crank

Post by cbrew »

I will refer to the prints again. But I am 99% sure it calls out a 90 degree eccentric crank. I will message back in a few
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kenrinc
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Re: quartering the eccentric crank

Post by kenrinc »

Cbrew,

That is probably true! I should have pointed out that it's dependent on the design of the gear!

Ken-
srrl5
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Re: quartering the eccentric crank

Post by srrl5 »

cbrew wrote:Hi Dave,
I am focusing on quartering the crank its self. other then eye balling with a square

O
|
O-O
My description is for locating the crank. But it also gives you the correct length for the eccentric rod.

David
We the willing, led by the unknowing, have been doing so much with so little for so long that we are now qualified to do anything with nothing.
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cbrew
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Re: quartering the eccentric crank

Post by cbrew »

OK thanks Dave. I will have to go back and re read it. Just in a hurry to get to making chips. Vacation is going quick :) any ways. I did look at the prints. It does not call out the position in degrees but does call out the eccentric circle... and with the crank machined to print. That should probably be where I start. BTW this is rhw Allen baker design.
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srrl5
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Re: quartering the eccentric crank

Post by srrl5 »

I've always made the eccentric rod to "fit" instead of to the "print" even with every part machined to print I've found as much .100" difference from side to side on the eccentric rod to make the loco run square forward and reverse.

David.
We the willing, led by the unknowing, have been doing so much with so little for so long that we are now qualified to do anything with nothing.
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cbrew
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Re: quartering the eccentric crank

Post by cbrew »

That is correct. The crank is to print not the rods. In fact the rods are from from print since this gear is not intended foe the ten wheeler.
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Asteamhead
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Re: quartering the eccentric crank

Post by Asteamhead »

Hello Chew,
Using the dockstader program, I tried to answer your questions.
First, there is no difference between baker and walchaert valve gears regarding the adjustment of the valve crank.
Diagram 1 is showing angles at pos. 180 ° of the main crank, diagram 2 at pos. 0 ° . The front joint of the ecentric rod should be in exactly the same (neutral) position at both angles. This is still mandatory in case the joint of the excentric rod is not at the same height as the center line wheel-cylinder, which is shown here. This is achieved by adding an angle phi h to the otherwise 90 ° between main crank and valve crank.
Length of the excentric rod should fit then to the neutral (no movement!) position of the valve gear as shown.
The right angle / position of the crank may be (fine-) adjusted this way in case the crank hat been removed for any reasons. Fastening of the valve crank is recommended by use of clamp the split cank arm by two bolts.
Good luck!
Asteamhead
Attachments
Baker pos. 180 deg.pdf
Baker Diagram 1
(327.56 KiB) Downloaded 256 times
Baker pos. 0 deg.pdf
Baker Diagram 2
(285.39 KiB) Downloaded 250 times
Typical US style valve crank with two bolts (M 4)
Typical US style valve crank with two bolts (M 4)
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cbrew
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Re: quartering the eccentric crank

Post by cbrew »

hmm, maybe i did not make my question clear in the original post,
I am not looking for rod lengths etc.. I am looking for ideas i setting the crank itself.. I did it by eye before and was successful

i have to do it one more time as i have completely disassembled it for painting etc.

I plan in drilling and pinning the eccentric crank once she is finely tuned as close as possible (the main crank pin is already pinned in the wheel)


going back together.jpg
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