Guided Rubber-tired tram question

[Cloudship]

I saw a post at one time on this on the boards, but I can't find it now. Anyway, I have a question regarding the Translohr and the Bombardier GLT vehicles.

Both of them use/can use a guide rail for guidance. On a conventional light rail vehicle, each boggie (wheel set) is able to rotate, so that the vehicle follows along the curve precisely. In a conventional bus, only the from wheel set rotates. What this means is that the further back you are in the vehicle, the more "swing" you have - the back of the bus makes a much tighter arc than the front. This is one of the reasons why I find buses less comfortable to ride on.

In the guided rubber tired vehicles, are both wheel sets able to rotate, or is it just the front axel? I am assuming that both vehicles have both a front and rear axel on each car, if so do both rotate?

[queetz@home]

I bumped the guided bus thread for you so you can research your info and post over there. I think only the Translohr has bogeys that rotate. The rest of them are buses dressed up to look like trams, which is really devious.

http://www.skyscrapercity.com/showthread.php?t=206821

[greg_christine]

The following is the website for Translohr:

http://www.lohr.fr/transport-public-tech.htm



The Translohr website features the following illustration of a bogie:



If I am interpreting this correctly, the vehicle is supported on a series of single-axle bogies that each have sets of guiding wheels at both the forward and aft ends of the bogies.

I have not seen any information on the bogie set-up for Bombardier's GLT vehicles. I would assume that all the bogies would have to pivot in order for all wheels of the vehicle to follow the guide rail around curves. The interesting issue for the GLT vehicles is that they must also be able to function as conventional unguided buses, which would require controlling the pivot mechanism of the aft sets of wheels.

[Cloudship]

Thanks! Unfortunately, I don't read French, so I didn't get much from the translohr site.

In reading up, I noticed the Translohr is able to go off track, which would imply that the rear wheelsets are stationary. Or does that change depending upon whether it is on or off the rail? I am not sure that each car exactly follows the rail on either the translohr or the GLT.

[greg_christine]

Originally Posted by Cloudship

In reading up, I noticed the Translohr is able to go off track, which would imply that the rear wheelsets are stationary. Or does that change depending upon whether it is on or off the rail? I am not sure that each car exactly follows the rail on either the translohr or the GLT.

The following report has some additional information on Translohr and Bombardier's GLT/TVR:

http://www.calstart.org/programs/brt...rip_report.pdf

The Translohr vehicles have operator stations at both ends and can operate in either direction. Based on this, I think it is safe to assume that at least the end bogies are guided. My guess is that all the bogies are guided but I have been unable to find confirmation of this. Regarding the ability of Translohr to operate off the guide rail, the report states the following:

"In the present design, the vehicle is not intended to leave the guidance rail but it can operate “off-rail”, in a battery-only mode, for short distances."

The Translohr vehicle utilizes a pantograph that contacts a single overhead wire. The guide rail serves both for guidance and as a ground. The guide rail must be present to complete the electrical circuit.

Bombardier's website states that the GLT/TVR vehicles feature an onboard diesel generator for off-rail operation:

http://www.bombardier.com/en/1_0/1_2/1_2_2_2_1_1.jsp

Pictures of the installation in Nancy, France show a two-wire overhead electrical supply as used for conventional trolley buses. With this configuration, the vehicles could operate under electric power even where the guide rail is not present. The same vehicles are also used in Caen, France except that installation features pantographs and a single-wire electrical supply.

http://homepage.ntlworld.com/c.fuller1/Tvr.html

There have been a series of highly publicized accidents involving GLT/TVR vehicles partially coming free from the guide rail. Descriptions of the accidents refer to the aft sections coming out of line, which implies that all the wheels are guided when operating on the guide rail.

[Cloudship]

Well, apparently the Bombardier TVR (which I think is actually an earlier version of the GLT) had tack wheels on the first and third axels. I think it is no wonder then that that it WOULD derail, because the back end of the first car is not tracking precisely around the corner. Even if the next axel was articulated and had a track wheel, it would not precisely want to follow the track.

I actually like the idea of a rubber tired tram - I think ruber wheels provide better ability to handle grades. But Ithink every axel needs to be rotatable, AND needs to have a track wheel. This would mean that it would be nearly impossible to run it off track, but I think that is a viable tradeoff.

[spsmiler]

Originally Posted by Cloudship

Well, apparently the Bombardier TVR (which I think is actually an earlier version of the GLT) had tack wheels on the first and third axels. I think it is no wonder then that that it WOULD derail, because the back end of the first car is not tracking precisely around the corner. Even if the next axel was articulated and had a track wheel, it would not precisely want to follow the track.

I actually like the idea of a rubber tired tram - I think ruber wheels provide better ability to handle grades. But Ithink every axel needs to be rotatable, AND needs to have a track wheel. This would mean that it would be nearly impossible to run it off track, but I think that is a viable tradeoff.

Actually, the GLT was the prototype, and the TVR is the "real thing". At one time I had some info which showed that the rear wheels follow the exact path of the front wheels - so if the ground had snow on it there would be only one set of tracks.

In Nancy they include sections off the track (ie: the driver steers!) . When i was there I only saw this happening in electric two-wire mode, although i understand that when the system first opened there was a deviation away from the overhead wires where they operated in diesel mode too.

In Caen the TVR remains in guided mode at all times when in passenger service - but to reach the garage they use driver steered diesel-electric mode.

There is more info here (my web site) - note however that I am working on an update on this page and within the next few days will be adding a lot more information about the Translohr and Phileas.

http://www.garden.force9.co.uk/Buses03.htm

Simon

[ssiguy2]

With rubber tires I can't imaging it would be great in colder/snowier climes