Scalefour Forum

http://clag.org.uk/2nd-gen-mu.html

Not sure when these will be available.

(Edit: whooops! Apologies to early viewers of the above page - I got the wheel diameter references wrong. Now corrected. Shows you how much I know about modern MU bogies!!)

Can you power both Axles Russ?

Most second gen DMU's have a powered bogie and a trailing bogie.

2nd gen EMU's have all 4 axles powered but the wheelbase is longer anyway.

Cheers

Jim

jim s-w wrote:Can you power both Axles Russ?

I think that would be very unlikely in that particular design, Jim, because a through transmission axis would get in the way of other key bits of the bogie. The design is, primarily, one to see if an endframeless approach is feasible.

The point you make about most prototype second gen DMUs having a powered bogie and a trailing one is interesting, but begs the question whether we need to replicate the prototype approach at all. Driving only the inner axle of two bogies of one model vehicle makes sense in terms of vehicle weight-distribution, and is generally sufficient traction-wise. That's a Ted/Bill valid point of view, and I'm not criticising it. A significant factor in the endframeless pinpoint design is the amount of weight that can be put over the bogie. One could say it doesn't follow a true second gen approach, but then one could say that approach is really only followed properly with axle-hung technology, which is what Ted would be thinking of as the 'proper approach', particularly for multi-driven axles in modern EMUs. I rarely give a fig for such fidelities myself, and am a fan of single twin-axle drive bogies, because only one bogie frame needs significant modelling work! Quite a few years back, I knocked this up from a Bill B4 frame:


This is intended to be a single heavy (100g) drive, with parallel-ended axles and bearings for safety, of a 4-car unit. (There's no point in worrying about bearing friction on driven axles.) The complication is of course the transmission tunnel obscuring a conventional bogie mounting, and although I solved that to my satisfaction (a special shouldered bolt), and got the whole unit including the secondary spring plate within a 15mm headroom, I don't think Ted or Bill were sufficiently enthused or thought it was sufficiently 'productionizeable' at that time. The irony is that my twin-axle drive is intended for a 1st gen unit!

Ted and I argue about our mutual inconsistencies and compromises till the cows come home...

I'd like to think we're not quite as inconsistent as Bachmann though, with the initial trepidation over their 108 drive, getting cold feet about its traction and weighting it down with that absurd 400g mazak chassis, then going completely over the top with the monstrous 150 ("look, no interior!") drive, and then in a fit of strange confidence, putting the 108 drive in the marvellous 4-CEP to rapturous applause.

Russ Elliott wrote:

jim s-w wrote:Can you power both Axles Russ?

I think that would be very unlikely in that particular design, Jim, because a through transmission axis would get in the way of other key bits of the bogie. The design is, primarily, one to see if an endframeless approach is feasible.

The point you make about most prototype second gen DMUs having a powered bogie and a trailing one is interesting, but begs the question whether we need to replicate the prototype approach at all. Driving only the inner axle of two bogies of one model vehicle makes sense in terms of vehicle weight-distribution, and is generally sufficient traction-wise. That's a Ted/Bill valid point of view, and I'm not criticising it. A significant factor in the endframeless pinpoint design is the amount of weight that can be put over the bogie. One could say it doesn't follow a true second gen approach, but then one could say that approach is really only followed properly with axle-hung technology, which is what Ted would be thinking of as the 'proper approach', particularly for multi-driven axles in modern EMUs. I rarely give a fig for such fidelities myself, and am a fan of single twin-axle drive bogies, because only one bogie frame needs significant modelling work! Quite a few years back, I knocked this up from a Bill B4 frame:

Hi Russ

Second gen DMU's do not have traction motors - they have a central motor driving one end through bogie mounted gearboxes. The design is nearly there - It would be easy enough to make the gearbox thrust thingie into an S shape rather than a U shape so that should shift that part out of the way. If the gearbox is high enough then a simple hole will be all you need.

You should be able to hide a motor in the moulded motor area of a 150 and the drive shaft to the inner end would look very like the real train. Drive shaft to the other end would look decidedly odd though.

Do we need to follow the prototype? No, of course not but at the same time if you are this close then why not? Having said that the bachmann 150 with a straight wheel swap has no problems on some really bad track. I do need a replacement bogie for the trailing end of the driven car though so you never know!

Cheers

Jim

I understand and appreciate what you're saying Jim, but I'm not the person to convince! Getting two UJs/couplings that can take the required torque within a 22mm (say) space is not easy, and a transmission tunnel would add a degree of complexity to the swing arm arrangements that might be difficult to engineer reliably, especially for pinpoints.

Ted has been hacking one of the new bogie frames for a twin-axle drive. Despite me thinking the transmission axis might interfere with the swing-arm pivot axis, it turns out there is adequate room after all. The following pic is 'work in progress', and Bill is changing the gearboxes (the torque reaction arms are not in a great place!) and tweaking the bogie artwork:

Russ, without meaning to ask a stupid question...

I assume these are all test etches? How do you get them from Bill Bedford? I'm particularly interested in the secondary springing units for his coach bogies, and these are not listed in the Eileen's website.

Regards

Matt

Matt - yes, fair to say they are test etches at the moment, and they won't be released until the next one with the new mods is proven. Regarding availability of his stuff, I'm not quite sure what the 'dividing line' between Bill and Eileen's is, and I guess it is something of a moving target. As far as I know, the secondary springing units (pics here) became production items quite a while back, but I can't see it listed either on Bill's new site or on the unstructured chaos of Eileen's Bill list.

I suggest e-mailing Bill will be the simplest way of finding out how to get them.