Scratchbuilding a tender drive

[chris p bacon]

I've got some ideas for making up a tender drive but before making a start wonder what others are out there or what experiences people have had. 

 

On my thread I've been making up some early GN locomotives which start as 3D prints, the bodies themselves are just the ticket but for one locomotive powering the drivers is proving problematic. The one in question is a GN B3 2-2-2 with a 7'6" driver, it is a really small boilered loco with little room to add weight, the chassis is actually quite long to be rigid and so if it encounters any problems she slips to a stand easily.

This is the chassis so far.

There are pick-ups on all wheels and I've introduced an element of compensation to the leading and trailing axles but as I encountered mucking about with a Kitmaster Single there just isn't enough room to add weight over the driver when the motor is fitted.

 

So instead I am going to try a tender drive, it doesn't need to be able to haul 10 heavy MK1 coaches although I'll try and make it as powerful and heavy as possible. Powering one axle is easy enough with a simple motor and gearbox but I'm wondering about making up a geartrain to power at least one other or ideally all 3 tender axles.

 

Searching here just gives results for Hornby tender drives so can anyone point me in the direction of what I might be after, I've looked at High Level and LRM and obviously they have something for single axle but what about all axle drive.

[uax6]

Could you use two gearboxes, one on each end of the motor? One would have to be mounted backwards so that it drives the same way as the other mind.

 

Can you get rid of the wires over the top of the chassis by running them underneath (Like a small busbar) which would then leave more space for the lead. Fill the body with plasticine and then put it on the chassis, and it will give you the amount of space available for lead over the motor. And I think you can get some under the motor in the chassis gap too. Can you fill the sandboxes as well?

 

Thinking about it, could you put weight over the driver and the rear wheel, so that she is heavy on the back, which would also help with pickups?

 

Andy G

[chris p bacon]

Could you use two gearboxes, one on each end of the motor? One would have to be mounted backwards so that it drives the same way as the other mind.

 

Can you get rid of the wires over the top of the chassis by running them underneath (Like a small busbar) which would then leave more space for the lead. Fill the body with plasticine and then put it on the chassis, and it will give you the amount of space available for lead over the motor. And I think you can get some under the motor in the chassis gap too. Can you fill the sandboxes as well?

 

Thinking about it, could you put weight over the driver and the rear wheel, so that she is heavy on the back, which would also help with pickups?

 

Andy G

The 2 gearboxes is a thought although I was thinking initially they would turn in different directions.....?

 

The wires are only a temporary addition to link the 2 pick ups, I'd thought of running them underneath as a bus bar but there really isn't much room to go around the gearbox.

 

Part of the problem is if there is more weight added to the front or rear she doesn't sit right and it takes the weight off the drivers but the motor and gearbox preclude being able to add more above them.   Just as a bare shell with the motor wheels and chassis it weighs no more than 30g. The G1 which is a 0-4-4 but has a little more room with side tanks is now 140g with room for a bit more lead.

[uax6]

How about fitting the motor in the smokebox, and extending the shaft to the gearbox? Then you will be able to pack the area around the  gearbox with lead.

 

The two gearboxes will both have to be facing the same way round, so you will only be able to secure the motor to only one of them.

 

Andy G

[Horsetan]

The 2 gearboxes is a thought although I was thinking initially they would turn in different directions.....?

 

Yes and no. One box on one shaft works forward, whilst the other shaft works in the same direction, even though its box faces the other way. If they didn't how would all those new RTR diesels work?

[davetheroad]

If you don't want to build your own drive take a look at this Australian site

 

http://www.hollywoodfoundry.com

[relaxinghobby]

Your chassis looks like a very neat and well make example, ideal for an all wheel drive 6 wheeler, but takes away weight from the drivers on a single.

 

For a single driver engine drive, try making the chassis flexible with as much weight bearing down on the driving wheels as possible and a weighted tender resting on the draw bar.

 

That's the Mike Sherman method.

 

Drivers and rear wheels are an 0-2-2 unit with the rear wheels given some lateral up and down movement. The front wheel is just there for show on a flexible pony truck, bears almost no weight. Extra pick ups on the tender.

Load up the boiler and free spaces with lead.

 

 

 

This little single, based on a Glasgow and Edinburgh Rly Beyer Peacock can romp along with three bogies.

 

[uax6]

Heres a thought: How about driving on the leading and trailing axles and making the driver a floater? Centrally mounted motor with long shafts driving gearboxes on front and rear axles, and as much of the body and chassis stuffed with lead as you can?

 

Ok you won't be able to spin the drivers, but your drivers won't dare do that would they?

 

Andy G

[hayfield]

Dave

 

How about one of the Highlevel motor drive options, have a chat with then either at a show or on the phone. The chap is very helpful and may be able to offer a few options/ideas

 

Keyser used a double ended motor shafts for both tender and bogie drives

 

Highlevel has a 10' wheelbase on the long rider, Quad driver may be an option, The Fly shunter, the Low Rider bogie or Pacemaker. On the other hand one of their gear box arrangements with the appropriate configuration at each end of a twin shaft motor

 

http://www.highlevelkits.co.uk/

[28XX]

Heres a thought: How about driving on the leading and trailing axles and making the driver a floater? Centrally mounted motor with long shafts driving gearboxes on front and rear axles, and as much of the body and chassis stuffed with lead as you can?

 

Ok you won't be able to spin the drivers, but your drivers won't dare do that would they?

 

Andy G

Mount the 'driving' wheels on stub axles with a long-shaft motor between them, driving the leading and trailing wheels.

[chris p bacon]

I've been sketching out what I can fit and the tender does seem to be the most likely location, the boiler is just not that big and there is 'air' between the frames and barrel behind the smokebox which I'd like to keep.

 

Looking at options it's looking like a double ended motor with 2 - 30:1 gearboxes, if I use the  Roadrunner on one axle I could use the Roadrunner plus on the other, I could then use the swinging arm to achieve the right wheelbase as well as tip the motor up. I still intend to use the drivers for a pick up and the chip will have to go in the loco as there isn't enough space in the tender with weight added, I'll pop into Maplins to see what plug/sockets they have as there might be something suitable in there as I'd prefer not to have them permanently wired.

 

Time for some sketching....

[chris p bacon]

Time for some sketching....

And the sketching is done...

 

So here is the tender I'll use, it's one of JCL's 3D prints that goes with an Ivatt A5 single.

There's a reasonable amount of room inside it

The sprue you can see is the buffers and brake blocks.

 

So using the 3D print of the tender and the drawing it was based on, I came up with some dimensions for the internal size of the tender, I drew it out on some graph paper then in the old fashioned way printed some templates from High level (checking the sizing) then cut them out and stuck them together

What I've come up with is a 1430 motor with a Roadrunner compact+ at each end, the swinging arms allows it to sit under the coal shute at the forward end and swing up at the rear to fit with the 6'6"+6'6" wheelbase. There is still room above the motor and between the motor and chassis to fix some sheet lead for weight. Gearing is 30:1 and should give a top speed of 55-60 which isn't quite prototypical but I think will work ok.

Chassis -  I could make it from some sheet brass or I might use some styrene box section as that can be carved up and it's easy to fix pick-ups to.  

 

If it works I'll put one in the Kitmaster Stirling single tender when I return to that one (when I source some cylinders) 

[billbedford]

On my thread I've been making up some early GN locomotives which start as 3D prints, the bodies themselves are just the ticket but for one locomotive powering the drivers is proving problematic. The one in question is a GN B3 2-2-2 with a 7'6" driver, it is a really small boilered loco with little room to add weight, the chassis is actually quite long to be rigid and so if it encounters any problems she slips to a stand easily.

 

If you use one of these motors or one of these you should be able to get it and enough ballast into the boiler.

[Guy Rixon]

 

If you use one of these motors or one of these you should be able to get it and enough ballast into the boiler.

 

 

Yes, but would it have enough power? I've not heard of these being used for 4mm-scale standard gauge, except for those power bogies under the CLAG EMUs.

 

Concerning the proposed tender drive: how is the second gearbox secured to the motor? Does the motor have fixing holes at both ends?

[billbedford]

Yes, but would it have enough power? I've not heard of these being used for 4mm-scale standard gauge, except for those power bogies under the CLAG EMUs.

 

 

The 8 x 16 is what powers the Kernow Beattie well tank and the LSWR O2.

[garethashenden]

I used one of High Level's motor bogies to power a tender. I added a middle axle to match the prototype, but only the outer two are powered.

 

[chris p bacon]

 

If you use one of these motors or one of these you should be able to get it and enough ballast into the boiler.

Thanks, very interesting, I should have taken a better picture as what you can't see is the Gearbox is the part that takes up a lot of the available room and inhibits the addition of weight. The motor is actually slung behind the drivers

 

Yes, but would it have enough power? I've not heard of these being used for 4mm-scale standard gauge, except for those power bogies under the CLAG EMUs.

 

Concerning the proposed tender drive: how is the second gearbox secured to the motor? Does the motor have fixing holes at both ends?

The motor has fixing holes at each end (as far as I know) if not I'll make something up, did something similar years ago and it seemed to work. 

[chris p bacon]

I used one of High Level's motor bogies to power a tender. I added a middle axle to match the prototype, but only the outer two are powered.

 

Thats nice and neat, how did you get on with gearing? 30:1 is about the best I can get which gives a scale 50-55 which for me is fast enough, did you put pick ups on the drive or the loco body?

[garethashenden]

Thats nice and neat, how did you get on with gearing? 30:1 is about the best I can get which gives a scale 50-55 which for me is fast enough, did you put pick ups on the drive or the loco body?

High Level offer three ratios 1:27, 1:36, and 1:48. I don't know which this was. I built it for someone else and he supplied all the parts. I fitted pickups to the two driven wheels. I had them fitted to all three axles, but the middle axle wouldn't turn afterwards, there was too much pressure. If you do use this method, don't use the designed in compensation. The middle axle gets in the way of the compensation and the bogie can't move itself, let alone anything else.

[billbedford]

Thanks, very interesting, I should have taken a better picture as what you can't see is the Gearbox is the part that takes up a lot of the available room and inhibits the addition of weight. The motor is actually slung behind the drivers

 

 

This is a schematic of frames for a LSWR T9 with a 8 x18 motor mounted in the fire box. The red circle shows the position of the single's trailing axle relative to the driven.  This arrangement would appear to leave most of the boiler free for ballast.

 

 

[Edwardian]

I wonder what the wheel diameter and centres are for the GN tenders?

 

I seem to recall some with an unequal w/b, but most seem to have equal spacings, as appears to be the case with JCL's print.

 

Most tender wheels seem to be around 4'/16mm, and tender motor units are made with such wheels to a variety of equally spaced w/bs: http://motorbogies.com/index.php?main_page=index&cPath=1_5_10

[chris p bacon]

This is a schematic of frames for a LSWR T9 with a 8 x18 motor mounted in the fire box. The red circle shows the position of the single's trailing axle relative to the driven.  This arrangement would appear to leave most of the boiler free for ballast.

 

 

LFF3102 Frames.jpg

Thanks Bill that's interesting.

 

The T9 has a 6'7" driver which is a little smaller than the 7'6" of the B3 but it still needs a low ratio so I wonder what they used for a box. for comparision this is the side on view of what I have so far.

And this gives an idea of what is above the driver

To get the gearbox up so it couldn't be seen and then twisted about so it would actually fit within the body I tried a High Level Slimliner+ with Drive stretcher and managed to fit 60:1(or thereabouts) gears which spin it at a fairly prototypical speed

I'll have a sketch and a play with templates later as it looks an interesting option bit the motor would be visible on the footplate. 

 

I think I now see why Rapido are taking their time over No1 

[5050]

The 'Adavoyle' system might work. The design goes back to the early 80's (and probably much earlier) but the basic concept is still viable.  It comprises a motor in the tender with a thin steel shaft to a gearbox in the loco driving through universal joints and split axle current collection via the tender wheels.  I suppose you could also use the loco wheels as well.  PM me with your e-mail address and, if you would like, I can send you the details.

[JCL]

Hi Dave, it'll be interesting to see how you get on. I'll bet you're pleased we did the large version, not the intermediate one, as you'd have even less space.

[DCB]

 

Coming to this post rather late I seems to me that the answer is to power the trailing axle as well as the Driving axle.

I know they are different sizes but there are two options, different gear ratios for the two axles, or different motors

for the two axles. I think a horizontal motor in the tender driving the leading and trailing tender axles and also the

trailing loco axle through a drive shaft /cardan shaft with universal joints. As an added bonus DCC types could have the

driving wheels slip furiously a few times before powering up the main drive motor to actually move the train.