HST - How many coaches should it pull?

[Stephen-1214472]

Hello

I have a Virgin livery intercity 125 with what I was told is a Chinese 5 pole motor. It came with 2 scale coaches and a dummy car.

I also have a Virgin livery class 47 from the Night Mail Express set, which has two stubby coaches and mail coach (which I don’t use)

Lastly I have 2 MK3 coaches from my childhood 125.

As a test I tried to see what the HST could pull, it seems to manage 2 scale coaches, 2 stubby coaches and the dummy. Any more and it just sounds like it’s wheel spinning or the motor is racing, I’m not sure which it is.

The class 47 can pull the lot, with ease, both scale coaches, both Virgin stubbies, both mk3 coaches and the dummy car.

As a born worrier my first thought was, my HST is busted! But now I’m wondering if it’s just a limitation of the train itself?.

The HST is immaculate and runs smooth and quick when pulling smaller loads, there are no noticeable problems with it at all

Is there a reason the Class 47 can pull more? It does have more wheels and is heavier? Maybe this is why?

[Chrissaf]

Weight of the loco is a very significant factor in pulling power. The more weight that bears down through the wheels onto the rails, the more grip there is.

Many years ago, Hornby had a feature called 'Magnahesion' where a loco had a large magnet inside it. The magnet was attracted to the STEEL rails that were common at that time. The magnet attraction created greater downforce without any significant increase in actual weight, thus less strain on the motor. Magnahesion is now obsolete and wouldn't work anyway with modern Nickle Silver track as NS track does not stick to a magnet.

[Going Spare]

Loco weight can certainly be a factor in haulage capacity but the condition of its traction tyres is another. Are those on the HST gripping the wheel (they may have expanded slightly) and do their surfaces look glazed (so that they too easily slip on the rail)? Some Ringfield motors also suffer from the pinion gear becoming loose on the motor shaft but this is very rare on a 5-pole unit.

[ColinB]

I assume your Virgin HST is the old sort that uses the powered bogie. I also assume the motor you are talking about is a Ringfield five pole motor. I used one of those to upgrade my 1980s HST. The big issue you get is that the powered bogie is the one at the back of the loco, so it has difficulty getting traction. I found that traction tyres are critical also I added a bigger weight (Peters Spares does them). Then you have to worry about drag from the dummy unit, if you have added pickups to it that causes quite a lot of drag. To test, try removing the dummy unit, I bet it pulls a lot more coaches. I have recently bought the latest HST from Hornby that powers both bogies, I haven't tried it yet but I gather that pulls a lot more coaches, unfortunately at a very hefty price.

[Stephen-1214472]

Thank You Chris.

I have an old green diesel loco from the 60’s that has magnets in it. I was told that the brushes are so close to toast it only gets an outing on a very special occasion.

Does it sound normal / right that 4 coaches is about it’s “happy limit”. I’ve read some where a chap stating his also only managed 4 and that removal of weights in the dummy helped allow him to pull 8, but he was quickly contradicted by someone else who suggested that this shouldn’t be the case.

So I’m unsure if my HST is ok or not. Before I get fleeced by a shop to check it I thought I’d see what the internet thinks

[Stephen-1214472]

Thank you Colin, you are right on all accounts.

I believe it is a 5 pole ring field motor that uses the powered bogie and yes, minus the dummy car it can pull a lot more.

I was extremely surprised that the class 47 just pulled away like … well … like a train !! It was effortless, and I think it may have the same motor as the HST.

[Stephen-1214472]

Loco weight can certainly be a factor in haulage capacity but the condition of its traction tyres is another. ..............

 

 

[The Doc]

I owned a Hornby (UK made version) HST at one time, and I recall that it could only pull about 3 coaches plus the dummy unit without slipping (when on sharp train-set curves). The dummy driving unit is the big problem because its bogies are just like the trailing unit on the powered bogie - the wheels run inside a mazak metal block rather than having pinpoint axle bearings like the coaches.

[ColinB]

When I was having issue with my HST I did a lot of experimentation. The main conclusion I came to was that it was due to the power bogie basically pushing the power car along, whereas with say a class 47 with the same motor, the power bogie is at the front. Then you have the issue of the power bogie not having enough weight on it as it is right at the back, so it has a tendency to want to rear up. I took the weight out of the dummy car and then realised it needs it, to stop it sliding along the track. A class 47 has a wider wheelbase so perhaps that is why it has more pulling power. Funny I don't notice the same issues with my Pendulino but perhaps Hornby had more time to get it right. It would be interesting to find out how well the modern Railroad HST performs.

[atom3624]

With the powered unit upside down, if you hold each of the tyred wheels, can you move the tyre / does it slip around the wheels?

Another test, if placed onto the rails and pushed gently, can you feel a 'good resistance', no extra weight on top, just pushing along?

With good tyres on, not slipping around the wheels (stretched for example) and in good condition, you should feel a reasonable resistance.

Al.

[Patrick-1207881]

Check if your dummy has a weight in it. If so remove and put it in the powered unit and see if that helps.

I'm testing this myself.

Patrick

[Potterton]

@ Patrick: Check if your dummy has a weight in it. If so remove and put it in the powered unit and see if that helps.

I'm testing this myself.

I would caution against this. It may well help with the pulling power of the HST, but will probably lead to derailments when using the powered car to push the train with the "dummy" leading. The weight in the unpowered car is there for a reason in that it provides stability, especially over points and when negotiating "train set" curves. Add extra weight to the powered car by all means, but leave the weight in the unpowered car in place.