Watchind a Guilford frieght do some switching the other day, I noticed that there were only two brake cylinders visible on each side of the loco, one of the 500 series engines purchased from CN, compared to four on a conventional GP-40-2. Can someone explain this?
Railroad Forums
GRS 500 series units, reduced braking capacity?
- Discussion of Electro-Motive locomotive products and technology, past and present. Official web site can be found here: http://www.emdiesels.com/.
Moderator: GOLDEN-ARM
Only two brake cylinders on each truck? I'm not sure, though the two brake shoes on one side might be mechanically connected to operate on the same cylinder; Some big, new GE and EMD locomotives have four brake cylinders per one C-series truck. If the brake cylinders are not to operate more than one brake shoe, your locomotive would have a decreased braking-capacity.
I have to ride seven kilometers to get to my railfanning-spot... and other teens think they have it hard!
CN sold 20 GP40-2LW units to Helm Financial in 2000 who, in turn, sold them to Guilford Rail Service (MEC) in 2000. The GP40-2LW were from the 94xx - 96xx series. CN 9408 became MEC 500, for instance. CN has some of their mechanical drawings available at CNR Photos.com. This is from their site: http://www.cnrphotos.com/gallery/main.p ... emId=20601 Under 'Mechanical' its marked as having "single brake shoe rigging". So, yes, they have reduced braking capacity. I assume this was done to save money on CN's part but there might have been a better reason, and I kinda hope so.
The answer is simple: The ex-CN GP40-2LW's have Blomberg "M-type" trucks and the GP40-2's have older "standard" Blomberg trucks. Single-shoe braking is not a money-saver on CN's part (although an accident did happen last year on one of these units because the braking system was not maintained).
M-type trucks became optional starting with EMD Dash-2 production in the 1970s. At the time, EMD was converting from 2 brake shoes per wheel to a single brake shoe per wheel, on both 4- and 6-axle units. Some railroads requested 2 brake shoes per wheel and others traded in older units whose trucks were re-used, with the result that many Dash-2 Geeps ride on older Blomberg trucks.
With both types of Blomberg truck, each brake cylinder operates two brake shoes. On standard Blomberg trucks, these shoes form "clasps" around the wheel and are linked by two horizontal bars passing under the axle and wheel bearing (straddling the wheel). On Blomberg M-type trucks, the brake shoes are on the inside rims only and are linked by a single bar per side, crossing under the swing hanger. M-type trucks also have rubber pads in place of the leaf spring and a shock strut over one axle.
The switch to single brake shoes per wheel does not mean the brakes are ineffective. What it does mean is that there are half as many brake shoes to replace.
Also, the laws of physics (levers) indicate that equal pressure would be applied to each wheel regardless of whether the brake cylinder is operating one or two brake shoes. In fact, on new six-axle units, one brake cylinder operates two shoes and the other operates a single shoe linked to the truck frame.
M-type trucks became optional starting with EMD Dash-2 production in the 1970s. At the time, EMD was converting from 2 brake shoes per wheel to a single brake shoe per wheel, on both 4- and 6-axle units. Some railroads requested 2 brake shoes per wheel and others traded in older units whose trucks were re-used, with the result that many Dash-2 Geeps ride on older Blomberg trucks.
With both types of Blomberg truck, each brake cylinder operates two brake shoes. On standard Blomberg trucks, these shoes form "clasps" around the wheel and are linked by two horizontal bars passing under the axle and wheel bearing (straddling the wheel). On Blomberg M-type trucks, the brake shoes are on the inside rims only and are linked by a single bar per side, crossing under the swing hanger. M-type trucks also have rubber pads in place of the leaf spring and a shock strut over one axle.
The switch to single brake shoes per wheel does not mean the brakes are ineffective. What it does mean is that there are half as many brake shoes to replace.
Also, the laws of physics (levers) indicate that equal pressure would be applied to each wheel regardless of whether the brake cylinder is operating one or two brake shoes. In fact, on new six-axle units, one brake cylinder operates two shoes and the other operates a single shoe linked to the truck frame.
--Michael Eby
--http://trainiax.net
--http://trainiax.net
Both GE and EMD seem to have the two-shoe cylinders on the inward-pointing side of their C-series trucks.
I have to ride seven kilometers to get to my railfanning-spot... and other teens think they have it hard!
If I remember correctly, the reduction in the number of shoes (and thus cylinders) was originally concurrent with the application of composite, instead of cast iron, brake shoes which were supposed to have better wear qualities. I've read a number of times that the first units built this way by at least two builders displayed serious brake fade in switching service, leading to a change back to clasp type brakes with cast iron shoes.
Somebody clarify or correct this if I'm wrong.
-Will Davis
Somebody clarify or correct this if I'm wrong.
-Will Davis
On a picture in a "TRAINS" magazine, I saw a GO F59PH with only one brake cylinder. Since I'm going to Toronto after tomorrow, I will check as to whether the whole fleet got that done to them.
I have to ride seven kilometers to get to my railfanning-spot... and other teens think they have it hard!
On a picture in a "TRAINS" magazine, I saw a GO F59PH with only one brake cylinder. Since I'm going to Toronto after tomorrow, I will check as to whether the whole fleet got that done to them.They all have Blomberg M-type trucks, thus one brake cylinder per side. This applies to the vast majority of 4-axle road and passenger units built after the Dash-2 series.
--Michael Eby
--http://trainiax.net
--http://trainiax.net
Thanks, Mike.
Yeah, I've seen the '59s, and they do have one brake cylinder per side.
Yeah, I've seen the '59s, and they do have one brake cylinder per side.
I have to ride seven kilometers to get to my railfanning-spot... and other teens think they have it hard!
The number of shoes does not always = less braking power. The change to single shoe /wheel was possible with the switch from cast to compositison shoes. I have seen units with clasp brake rigging (2 shoes / wheel) with composition shoes. I have even seen units with traded in trucks, which have the single shoe. Here on the D&H, our ex LV gp38-2s have 1 shoe, but one can see the brackets where the outside rigging was mounted, on the previous locomotive with these trucks.
Single shoe units use higher air pressure, usually about 72 psi. The clasp units have lower pressure. The independant apply and release mu hose can have between 0-45 psi. This depends on how heavily the engineer has the brake applied. The relay valve determines the pressure to the brake cylinders. This is so that units with various brake riggings can mu. If not, a unit with 72psi. would slide, while one with 27 psi would not do anything. On BN, the clasp rigging units had 45 psi, with the comp. shoes, vs. 72 for single. on CP, the clasp units only have 27-30 psi. Like I said, the work together because the ind. app. & rel. pipe pressures are standard. It is all up to the relay valve To provide the right pressure, for the required force of the shoe against the wheel.
On BN, we had many of the ex gp30 and 35, now GP39s with clasp shoes. After the ATSF merger, the outside rigging was taken off. They then welded a bracket to the spring plank safety strap. On a Blomberg truck, with clasp rigging, the pistions are linked to the inside shoes. At the bottom of the rigging, the inside rigging is leveraged against the outside. With the Santa Fe modification, ther wes no longer anything to leverage the inside rigging against. This was now connected to the safety strap. 2 cylinders were retained. The change was to the relay valve, which raised pressure to 72 psi.
Single shoe units use higher air pressure, usually about 72 psi. The clasp units have lower pressure. The independant apply and release mu hose can have between 0-45 psi. This depends on how heavily the engineer has the brake applied. The relay valve determines the pressure to the brake cylinders. This is so that units with various brake riggings can mu. If not, a unit with 72psi. would slide, while one with 27 psi would not do anything. On BN, the clasp rigging units had 45 psi, with the comp. shoes, vs. 72 for single. on CP, the clasp units only have 27-30 psi. Like I said, the work together because the ind. app. & rel. pipe pressures are standard. It is all up to the relay valve To provide the right pressure, for the required force of the shoe against the wheel.
On BN, we had many of the ex gp30 and 35, now GP39s with clasp shoes. After the ATSF merger, the outside rigging was taken off. They then welded a bracket to the spring plank safety strap. On a Blomberg truck, with clasp rigging, the pistions are linked to the inside shoes. At the bottom of the rigging, the inside rigging is leveraged against the outside. With the Santa Fe modification, ther wes no longer anything to leverage the inside rigging against. This was now connected to the safety strap. 2 cylinders were retained. The change was to the relay valve, which raised pressure to 72 psi.