I was noticing that the branch line near here is mostly 75 to 90 Lb rail with a mix of 4 bolt and 6 bolt tie bars. Mostly 4 bolt bars. The 6 bolt bars look a lot beefier than the lighter 4 bolts. What would be the criteria for using a 6 bolt joint bar instead of 4 bolt? What determines the proper joint bar to use? How are the holes for the bolts made? (drilled, punched or torched)
On another thread Mudchicken mentioned a Bulldog joint. What is this and what does it look like? Rail size transition joints are obvious. I see a few of these.
Thanks
Pete
Most 6-hole joint bars are longer than the 4-hole ones - typically 30’’ to 36’’ long, as opposed to 24’’ or so - it varies by rail section and joint bar design, though.
The primary goal of a joint bar - besides obviously mechanically connecting the rails and keeping them in close enough alignment on the tops and gage face with each other - is to replace the loss of continuity of the rail’s strength through the actual break at the rail end in each joint.
A 6-hole joint bar is used when the joint is wanted or needed to be as strong as possible against flexure or bending, such as preventing the rail joint from kinking outwards in curved track, and/ or making the joint as stiff as possible in the vertical plane so that the track is as strong as possible through the joint area, and the risk of a resulting ‘dip’ in the track surface there at the inherently weak point is prevented as much as possible. The additional 2 bolts in the 6-hole joint bar contribute to that by usually being a little farther out from the actual center of the joint than any of the bolts in a 4-hole bar - but mainly by adding 50 %* to the clamping force of the 4-hole joint bar, thus better resisting the tendency of the rail ends to kink or kick out of line in curves, and to keep the joint bars snug against the head and base of the rail to provide the vertical support. The ends of the rails are the stiffest portion when trying to bend the rail into a horizontal curve, and the hardest to keep in a unform curve because there’s nothing beyond the actual end of each ‘stick’ of rail to grab onto to twist or torque the rail into a curve, except via the joint bars as connected to the next rail.
*Mainly true only for modern, big/
Thank you Mr. Paul…
In addition, the number of bolts often is (or was) the choice of the individual railroad’s Chief Engineer as was the bolt hole spacing. We seem to be adopting the AREMA standard more these days.
Also, it was common to see eight bolt bars in some of the lighter weights (62#,66#, 70# and 75# rail comes to mind with even smaller diameter threaded bolts) with angle bars rolled to cover the base of rail (Making a lazy “L” shape) and spiked to the adjoining ties either side of the joint to stiffen the rail modulus.
If the railroad had lots of cycles (trains & tonnage) moving over a section of track, it often wanted the extra bolts as insurance against “blind joints” when too many bolts broke between inspections.
…and then there were the Weber joints with the wood filler that never seemed to stay tight. Almost as dumb is the still common site of a nut and bolt with more washers than one at the bolt. (The thing gets turned into a spring because somebody was too lazy to turn a wrench or go get the right length bolt)
Paul and Mudchicken.
I thank you. Paul you have done a fantastic job answering all my questions.
Mudchicken I still see a lot of the old wood filled joints. I have seen the stack of lock washers also. There is a mix of hex and square nuts on this line also. How tight are these bolts supposed to be? Do you tighten the first one until it breaks and then make the others just a little bit looser? LOL
BTW that must be one powerful punch to make them holes.
You guys are great.
Pete