bob1234 Posted March 11, 2021 Share Posted March 11, 2021 Hi, I've noticed without exception that all my modern Hornby tender locos (2x A4, 2x duchess, Princess royal, king and black 5) run slightly faster on a rolling road when the tender is not picking up power. They are all running on DC and with a hm2000. No other issues but just seems odd that all have the same characteristics. Anyone else seen this? Link to post Share on other sites More sharing options...
SteveyDee68 Posted March 11, 2021 Share Posted March 11, 2021 4 minutes ago, cbrooks122000 said: That is not surprising, the tender pickups will cause a certain amount of drag. Agreed on a layout, but on a rolling road? Also, it appears to be an electrical issue - note the OP says "when the tender is not picking up power". This is more of a mystery than first glance might suggest! Unfortunately, I have no explanation why, but as I own a few Hornby tender locos I am interested to see what might come of this observation! Steve S 2 Link to post Share on other sites More sharing options...
atom3624 Posted March 12, 2021 Share Posted March 12, 2021 Perhaps there's a poor connection between locomotive and tender? An added 'resistance' could have this effect, possibly? Al. 1 Link to post Share on other sites More sharing options...
gordon s Posted March 12, 2021 Share Posted March 12, 2021 (edited) I agree there is no drag on a rolling road, but something else is confusing me. The connection to the tender is via the small 4 pin plug. This connects to the DCC socket with an 8 pin blanking plug which in turn makes the connection between the loco pickups and the motor in DC mode. Unplugging the tender breaks that circuit and the loco won’t run as there is no connection between the loco pick ups and the motor. I can’t see how you can stop the tender picking up power on a rolling road unless you are specifically insulating the tender from the rolling road. Edited March 12, 2021 by gordon s 1 Link to post Share on other sites More sharing options...
Phil Himsworth Posted March 12, 2021 Share Posted March 12, 2021 2 hours ago, gordon s said: Unplugging the tender breaks that circuit and the loco won’t run as there is no connection between the loco pick ups and the motor. I have no experience with modern tender locos but I'm surprised they would be wired like this, and not just have the pickups wired in parallel with those in the loco so the tender is beneficial but not required. Unless the decoder is meant to be in the tender, I suppose. Could you measure the resistance between left and right wheels in the tenders alone? I wonder whether there is a high resistance path between the two sides somehow that is not enough to short out but enough to slightly lower the current through the motor to give the effect described...? Link to post Share on other sites More sharing options...
RMweb Gold MikeParkin65 Posted March 12, 2021 RMweb Gold Share Posted March 12, 2021 3 hours ago, gordon s said: I agree there is no drag on a rolling road, but something else is confusing me. The connection to the tender is via the small 4 pin plug. This connects to the DCC socket with an 8 pin blanking plug which in turn makes the connection between the loco pickups and the motor in DC mode. Unplugging the tender breaks that circuit and the loco won’t run as there is no connection between the loco pick ups and the motor. I can’t see how you can stop the tender picking up power on a rolling road unless you are specifically insulating the tender from the rolling road. I don’t think this is true of earlier locos which have the plug but the decoder socket is still within the loco. Certainly I have Britannia’s with this arrangement and they will run without the tender attached 1 Link to post Share on other sites More sharing options...
gordon s Posted March 12, 2021 Share Posted March 12, 2021 Certainly the Hornby locos I have where the decoder is fitted in the tender are wired this way. This is is to isolate the track and motor connections from each other and enable decoder installation on a plug in basis. You're right that early locos, had the DCC socket in the loco, but this involved removing the loco body, hence the change where possible to tender mounting. Link to post Share on other sites More sharing options...
Mark Posted March 12, 2021 Share Posted March 12, 2021 6 hours ago, atom3624 said: Perhaps there's a poor connection between locomotive and tender? An added 'resistance' could have this effect, possibly? Al. Is this on DC or DCC. There is no mechanism short of a high resistance short in the tender that could reduce the motor speed. Mark Link to post Share on other sites More sharing options...
bob1234 Posted March 12, 2021 Author Share Posted March 12, 2021 9 hours ago, gordon s said: I can’t see how you can stop the tender picking up power on a rolling road unless you are specifically insulating the tender from the rolling road. I'm simply lifting the tender up off the rolling road. The tender isnt disconnected at any time. All locos are the current models with 8 pin socket in the tender. I could understand a poor connection in one loco but not all. They have all had minimal use as my layout is currently dismantled so can only have done a max of 3-4 hours running each. 1 Link to post Share on other sites More sharing options...
Phil Himsworth Posted March 12, 2021 Share Posted March 12, 2021 Is there any weight transferred between tender and loco in normal use? By lifting the tender up, are you removing weight from the loco so it can turn the wheels more easily? 1 Link to post Share on other sites More sharing options...
Michael Hodgson Posted March 12, 2021 Share Posted March 12, 2021 51 minutes ago, 313201 said: I always thought it was that if the pickups are bearing hard on the wheels then yes I agree the pickups will cause drag and slow a loco down but if the pickups are set so they are not pressing too heavy on the wheels there technically shouldn't be any issues. I would have thought there would always be some resistance, and therefore some drag from any pickup. Obviously is the pressure of the pickup to the wheel is reduced there will be less friction - but perhaps at the risk of loss of reliability of the pickup if it breaks contact intermittently or altogether. The reason for all-wheel pickup is to reduce intermittent contact on iffy track, and increased drag is a trade-off against that problem. Link to post Share on other sites More sharing options...
RMweb Premium melmerby Posted March 13, 2021 RMweb Premium Share Posted March 13, 2021 6 hours ago, bob1234 said: I'm simply lifting the tender up off the rolling road. The tender isnt disconnected at any time. All locos are the current models with 8 pin socket in the tender. It can only be weight transfer, electrical connections, pickup drag etc. do not come into it. What happens if the tender is insulated from the rolling road without lifting it (e.g. some sellotape tape (other makes are available) over the rail to stop pickup) 1 Link to post Share on other sites More sharing options...
Nearholmer Posted March 13, 2021 Share Posted March 13, 2021 Leakage path via the rollers that the tender is standing on? Link to post Share on other sites More sharing options...
gordon s Posted March 13, 2021 Share Posted March 13, 2021 I'm always curious about something for which there appears to be no logical explanation, so I tried recreating the situation a few minutes ago with surprising results. This is a brand new Hornby B12 chassis undergoing my normal running in process. This is usually a couple of hours running in each direction in 30 minutes slots by gradually increasing the speed and reversing the direction. All set up on my rolling road under DC power and with the tender connected. I can't understand why it would make any difference other than the number of pick ups in contact with the supply, but here I have the opposite effect to that queried by the OP with the mechanism slowing slightly as the tender is lifted. There is no mechanical link between the two, just the wiring with the draw bar disconnected. Over to you..... Link to post Share on other sites More sharing options...
Porcy Mane Posted March 13, 2021 Share Posted March 13, 2021 (edited) On 13/03/2021 at 16:34, gordon s said: Over to you..... My Bachrus rollers have been exactly the same from new. The chassis runs slower when picking up via the rollers only due to increased electrical resistance through the roller bearings lowering the voltage available at the driving wheels. The solid mount the tender sits on has no resistance, so when the tender is placed on the mount the resistance of the rollers is bypassed providing full applied voltage to the motor. Simples. Edited March 15, 2021 by Porcy Mane 1 Link to post Share on other sites More sharing options...
RMweb Premium melmerby Posted March 14, 2021 RMweb Premium Share Posted March 14, 2021 20 minutes ago, cbrooks122000 said: It doesn't matter whether it is a rolling road or on the track, pickups on a tender will provide drag. Sorry, that is wrong. there is no drag on wheelsets that aren't turning (basic physics) 2 Link to post Share on other sites More sharing options...
BWsTrains Posted March 21, 2021 Share Posted March 21, 2021 (edited) I've a related issue with my King (2017 release) where pickup from Tender wipers is poor to non-existent. Now moved to a new Topic as a reference for others. Colin Edited March 21, 2021 by BWsTrains Moved to a new Topic Link to post Share on other sites More sharing options...
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