Speedy Con Rod Length Problem | Anyone Else Seen This?

This topic has 3 replies, 3 voices, and was last updated 27 December 2025 at 08:02 by Speedy Builder5.

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26 December 2025 at 18:16 #830070
lalan45
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@lalan45
I know the Speedy design is quite old, but I’m hoping someone here can help.

I’m having trouble with the connecting rod length. The drawings say the bearing centers should be 7.5 inches apart, but if I use that size, the crossheads hit the stuffing glands by more than 0.125 inch. This happens with the original drawings, and even with the later Don Young drawing 2A, where the clash is about 0.187 inch. As far as I can see, the con rod length wasn’t updated on the drawings I have.

My measurements assume the stuffing gland sticks out 0.375 inches from the cylinder cover, which allows about 0.125 inch for adjustment as the packing wears.

I’d really like to hear from other Speedy builders or owners. Did you run into this issue, and how did you fix it?
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26 December 2025 at 18:53 #830077
Speedy Builder5
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@speedybuilder5
I made mine 7 3/8″ which works OK, but its tight and once the gland “nut” sclackened back and jammed the whole caboodle!!

Also be aware that the brake hanger for the leading wheels fouls the back of the cylinder, so I did not fit them.

Other mods, super header, blower tube, installing boiler throat plate stays, bushing all boiler connections,installing mechanical braking system.

Good loco in spite of these mods.

Bob
26 December 2025 at 21:11 #830089
JA
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@ja
This is reported problem particularly when builders have modified the design. Looking at the Reeves drawings for my Speedy, the foward face of the Don Young cross head is 9.3125″ from the driving wheel axle axis while the rearward face of the rear cylinder cover is 9.500″ to the same wheel axle axis. That gives 0.187″ for the exposed part of the gland. OK, not very much but the LBSC cross head gives you another 0.0625″.

If you shorten the connecting rod you are changing the reversing gear geometry. If done, the combination should be moved rearwards by the same amount and the radius rod shortened. The wiser option is to try to move the rear face of the cylinder cover forward. Here is surplus metal such as the length of the gland boss.

Drawing things out, and now solid modeling, is a must before cutting metal. Did you start the build or buy a half built loco?

Wishing you, all, a good and interesting New Year. Just don’t shoot the messenger.

JA
27 December 2025 at 08:02 #830097
Speedy Builder5
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@speedybuilder5
Lalan, I have erred! I have just been down to the shed and measured the con rods – 7.5″ centre to centre although I have a pencil note on the drawings of 7 3/8″ ! Attached show the clearance between gland not and cross head.
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