Class 47 - Slow Speed Control.

[Richard Pike]

I am looking for information on Class 47 Slow Speed Control as fitted to the MGR machines.

 

I know there was a "Box" fitted to the Centre axle that I presume was fitted with a proximity switch or encoder and there was a controller mounted on the driver windscreen pillar to engage the system.

 

My particular question is how many axle "Boxes" where installed ?, i.e 4 x on each centre axle box or just 1 on a particular axle box.

 

I have reviewed a number of books and searched the t'internet and whilst there is lots of reference to SSC fitted 47's, there seems very little detail available.

 

Thanks for any help.

[Flood]

Just the one middle axle, at no. 1 end on the secondman's side.

 

I always try to get photos of all four corners of a loco if possible just in case there are any variations from the norm and this also helps with fitments such as SSC.

 

47168 SSC box visible:https://www.flickr.com/photos/brianews/5818336555/in/photolist-9S9uKv-dUN6rt-aEpadj-6u7ufG-gPsxrg-9TNq27-9S9yjD-dMxcZq-jMWy9R-9M7zWV-cmTuMd-7Hfuiy-dMpqE9-FtszD9-95jDPH-9M7zS2-bjcp5R-j1ueDP-aXdod4-hkDtY2-9Manq5-6S4TyC-kFgBAN-dzpJUr-amHWiv-BrRHyc-bfimnt-9M7zRk-diGeka-9zCLyU-dYZWJG-63cNTz-95TVWC-4B7ZLo-8A1fH3-o8MskA-P7fPvM-P7fPsk-Ny4jv2-NnuKPL-Kfu8ZA-Jo5Rwd-wsGUFe-vE9AhH-9EFiTc-bj3j8i-zPKWVu-eaRMbt-8zqw31-8pFzxT

 

47168 on the other side showing normal axle boxes:https://www.flickr.com/photos/dodger5450/25908645422/in/photolist-FtszD9-95jDPH-9M7zS2-bjcp5R-j1ueDP-aXdod4-hkDtY2-9Manq5-6S4TyC-kFgBAN-dzpJUr-amHWiv-BrRHyc-bfimnt-9M7zRk-diGeka-9zCLyU-dYZWJG-63cNTz-95TVWC-4B7ZLo-8A1fH3-o8MskA-P7fPvM-P7fPsk-Ny4jv2-NnuKPL-Kfu8ZA-Jo5Rwd-wsGUFe-vE9AhH-9EFiTc-bj3j8i-zPKWVu-eaRMbt-8zqw31-8pFzxT-7yU4Tq-dXwZD8-bj3j2c-f1fmZN-eNVjZD-8AinWT-9i8hbn-eiGiMk-ET6EiV-qYe7Gp-4TiAgw-eaRM7n-EYCyim

[Enterprisingwestern]

To some of us there was only ever one SSC fitted Brush 4!

 

 

 

Mike.

 

 

[Davexoc]

Just the one middle axle, at no. 1 end on the secondman's side.

 

Within said box is a toothed wheel and a proximity switch, which feeds all speedos with the SSC ones only reading when selected.

The cover is taken off for ultrasonic axle testing, and if you put the cover back on upside down it fouls on the teeth. Loco released and left shed, five minutes later the driver reappears 'Got half way down the yard and the speedo stopped working!'

Cover removed and out fell all the teeth.... Oops

 

Dave

[45125]

Within said box is a toothed wheel and a proximity switch, which feeds all speedos with the SSC ones only reading when selected.

The cover is taken off for ultrasonic axle testing, and if you put the cover back on upside down it fouls on the teeth. Loco released and left shed, five minutes later the driver reappears 'Got half way down the yard and the speedo stopped working!'

Cover removed and out fell all the teeth.... Oops

 

Dave

 

Not all 47s fitted with that style of speedo drive actually had slow speed fitted. The axle end box houses a toothed wheel and a magnetic pick up which has an  A C signal generated in it by the toothed wheel, this is then sent to the HSD speedo controller the out put from this drives the speedos in the cab, on SSC fitted 47s an other out put from the HSD speedo controller is sent to the slow speed control unit this then sense what speed has been set by the slow speed control in the cab (provide it has been switched in on the control cabinet in the engine room and the appropriate cab selected). The controller then balances the speed set to actual speed and controls the main gen excitation to the maintain the speed.

 

The speed o drive unit can also be fitted to no5 axle as well as no 2 axle.

[Davexoc]

Not all 47s fitted with that style of speedo drive actually had slow speed fitted. The axle end box houses a toothed wheel and a magnetic pick up which has an  A C signal generated in it by the toothed wheel, this is then sent to the HSD speedo controller the out put from this drives the speedos in the cab, on SSC fitted 47s an other out put from the HSD speedo controller is sent to the slow speed control unit this then sense what speed has been set by the slow speed control in the cab (provide it has been switched in on the control cabinet in the engine room and the appropriate cab selected). The controller then balances the speed set to actual speed and controls the main gen excitation to the maintain the speed.

 

The speed o drive unit can also be fitted to no5 axle as well as no 2 axle.

Can't remember the reason for the different types apart from SSC, may have been also tied in with speed diverts? Too many mods and variations......

The other type of speedo was more of a tachometer, generating a voltage to the cabs, not smooth enough for SSC.

Had another 47 stopped which was repeatedly reported as being 'low power, struggles to get over 80mph'. Speedos checked and both reading correct, but wheel-wear compensator hadn't been adjusted after tyre turning. At 80 on the clock it would have actually been doing almost 105mph, so 10 over the max speed for the class.

 

Dave