Flexi Chassis an Appreciation

This section allows guests to comment or ask questions. Posts from guests require explicit approval (which generally takes a day or so), before they appear, so that we can prevent unwanted spam.
User avatar
grovenor-2685
Posts: 3320
Joined: Sun Jun 29, 2008 8:02 pm

Re: Flexi Chassis an Appreciation

Postby grovenor-2685 » Wed May 17, 2017 9:22 pm

A a well-designed etched equalized chassis can easily be less complicated, even at the largest USA wheel arrangements - e.g. 4-8-8-2 and the less common UK ones - e.g. 2-2-2 and 0-4-4

Andy, you do keep making this sort of remark, but don't present any evidence for us to compare with the complexity of Mike Sharman's flexichas book or the S4 digest. Don't bother with the 0-4-4 or 2-2-2 as they are simple cases, the complexity comes with the big ones.
Regards
Regards
Keith
Grovenor Sidings

QuentinD
Posts: 30
Joined: Thu Sep 01, 2016 4:41 am

Re: Flexi Chassis an Appreciation

Postby QuentinD » Thu May 18, 2017 1:47 am

It's been suggested that somehow the CoG could end up in the wrong place--

At the design stage it's quite clear where the CoG is because the spreadsheet tells you as much.

When building there are drilling jigs for placing the fulcrum points if you go down that route, so no issues there. You'd have to be quite clumsy to mess that one up.

Lastly you have balancing. Perhaps the front is heavy, maybe the back, or whichever it is happens to be too light - simply add or remove weight until it's level before determining the proper spring thickness (or hey, it's fine as it is).

Ergo... the claim is bunkum.

Quentin

billbedford
Posts: 709
Joined: Tue Oct 02, 2012 2:40 pm

Re: Flexi Chassis an Appreciation

Postby billbedford » Thu May 18, 2017 7:59 am

Knuckles wrote:Ok, many thanks to you all for your input.

So what I'm gathering is the main thing really is to just establish the fulcrum points, build it and then simply try out different wire/spring thickness until the desirable spring rate is achieved. If so then great, problem solved.


...and move the ballast if necessary....
Bill Bedford
Mousa Models
http://www.mousa.biz

User avatar
Russ Elliott
Posts: 930
Joined: Thu Jun 02, 2011 6:38 pm

Re: Flexi Chassis an Appreciation

Postby Russ Elliott » Thu May 18, 2017 8:28 am

Armchair Modeller wrote:Out of curiosity, I just wonder how the experts test their chassis? Do they wait until the body is finished and run the whole lot as one, or have they worked out a way of testing the chassis alone? Thinner CSB springs, for example, to compensate for the lack of body weight, or do they weight the chassis temporarily to simulate a body on top?

https://www.youtube.com/watch?v=yyBtv5CE-KI

User avatar
Jol Wilkinson
Posts: 804
Joined: Mon Jul 21, 2008 7:39 pm

Re: Flexi Chassis an Appreciation

Postby Jol Wilkinson » Thu May 18, 2017 9:55 am

A look back at Will's opening post includes a quote from a well know advocate of CSB's that
"I would suggest that trying to get ...flexichas to work well has put more people off finescale than just about anything else."

I would suggest that recommending the use of CSB's would put off even more people. One of the benefits of compensation or "Flexichas" is the ability, with only a little care and planning, to get the loco "ride height" correct. If you get it a little wrong then "tweaking" the beam(s) will take care of it. Of course, I am willing to accept that as all my locos so far have been four or six coupled (bar one 0-8-0), they are all fairly straightforward. Despite proclamations elsewhere that Flexichass locos are less"stable" than sprung or CSB chassis, I haven't found that a problem and would suggest that, for most of us, it is something of a red herring.

Despite the claimed benefits of CSBs, using them does appear not as straightforward as some would have us believe. Firstly to have to identify the CoG of the loco "body", which means building it first (or at least stick all the bits on a piece of thick plasticard in their final positions to weigh it and find the point of balance). I have always preferred to build the chassis first so as to be able to check clearances on the body as I assemble it, something critical with those kits originally intended for OO alone - although the later generations of etched kits don't usually present those difficulties.

You then need to input your data to a spreadsheet to identify where the CSB mounts should go. Not too difficult, but more complex than working out where to put a compensation beam pivot. Next, where to put the vertical location of the CSB mounts? What if you get it wrong, especially with the recommended "drill holes and insert handrail knobs" approach? Even the full size thing often had the ability to adjust spring mounting heights though threaded J hangers. Why haven't soldered mountings that can, if the need arises, be un-soldered and moved, found more favour?

I have considered using CSB's but other than for 0-6-0's (I have only one of those left to build) the complication of arranging it for a 2-4-0, 2-2-2-0, 2-4-2T with radial trucks at each end, a 4-6-0 where the kit chassis design has the front frames and bogie pivoting ahead of the motorised bit of the chassis as one unit, together with several more 4-4-0's with sprung bogies, doesn't exactly inspire me to change what is for me, a pragmatic and sensible approach to P4 loco chassis.

I shall know go up to the workshop and do some model making, while the high priests denounce me as a heretic from their temple steps. :)
Last edited by Jol Wilkinson on Thu May 18, 2017 12:39 pm, edited 1 time in total.

User avatar
Russ Elliott
Posts: 930
Joined: Thu Jun 02, 2011 6:38 pm

Re: Flexi Chassis an Appreciation

Postby Russ Elliott » Thu May 18, 2017 11:00 am

That's all fair comment, Jol.

Philip Hall
Posts: 1426
Joined: Mon Aug 10, 2009 7:49 pm

Re: Flexi Chassis an Appreciation

Postby Philip Hall » Thu May 18, 2017 1:11 pm

I'm with Jol. Flexichas by choice because I know it works and I've done it for years. I also subscribe to the occasional rigid chassis. Perhaps I should duck at this point, but with truly round wheels and decent track they don't fall off and ride well, even at speed. I am also about to embark on a fairly large project and I want to get there as quickly as I can without taking time to experiment, when I have techniques that work perfectly already.

However, I am about to complete/repair a CSB chassis which worries me a bit. The customer has given me carte blanche to yank it all out and compensate if it gives me grief! Maybe I shall find out how easy (?) it is...

Philip

User avatar
Will L
Posts: 1801
Joined: Sun Jul 20, 2008 3:54 pm

Re: Flexi Chassis an Appreciation

Postby Will L » Thu May 18, 2017 3:30 pm

Russ Elliott wrote:That's all fair comment, Jol.

We feeling a bit defeatest today Russ? There's a fair bit there I think we could reassure Jol on. However trying to compose a complicated answer on a tablet touch screen ( I'm away on holiday) is more than I'm good for.

I shall be back

There a a few things in Andy recent post that need an answer too, but they tend to go back to Keith's responce. I've. Lest see a practical examples of say that N7 then we can discuss it further.

User avatar
Will L
Posts: 1801
Joined: Sun Jul 20, 2008 3:54 pm

Re: Flexi Chassis an Appreciation

Postby Will L » Thu May 18, 2017 3:39 pm

Armchair Modeller wrote:
Knuckles wrote:Ok, many thanks to you all for your input.

So what I'm gathering is the main thing really is to just establish the fulcrum points, build it and then simply try out different wire/spring thickness until the desirable spring rate is achieved. If so then great, problem solved.

This helps a lot, thanks.


That's certainly how I understand it, as another novice.

Out of curiosity, I just wonder how the experts test their chassis? Do they wait until the body is finished and run the whole lot as one, or have they worked out a way of testing the chassis alone? Thinner CSB springs, for example, to compensate for the lack of body weight, or do they weight the chassis temporarily to simulate a body on top?


For the build phase what you want to prove is that you have every thing set up square an accurate, so what you fit is a stiff wire (I use 20 thou) which on a bare chassis with no body hardly flexes at all. You can then check all the wheels touch the floor on a traditional bit of plate glass. When you know it is strait and true, and how heavy it us, then fit the right wire size. Also you will find it will run on decently laid track perfectly OK with the thick wires in. You only need the thinner wires to correct the ride hight and to deal with track that is less than perfect.

User avatar
Jol Wilkinson
Posts: 804
Joined: Mon Jul 21, 2008 7:39 pm

Re: Flexi Chassis an Appreciation

Postby Jol Wilkinson » Thu May 18, 2017 6:02 pm

Will L wrote:
Russ Elliott wrote:That's all fair comment, Jol.

We feeling a bit defeatest today Russ? There's a fair bit there I think we could reassure Jol on. However trying to compose a complicated answer on a tablet touch screen ( I'm away on holiday) is more than I'm good for.

I shall be back

There a a few things in Andy recent post that need an answer too, but they tend to go back to Keith's responce. I've. Lest see a practical examples of say that N7 then we can discuss it further.


Will,

I don't need reassuring. I am sure that CSB's work well.

The question is, would I get a perceivable benefit over what I do now, for the extra effort?

Enjoy your holiday.

Jol

User avatar
Russ Elliott
Posts: 930
Joined: Thu Jun 02, 2011 6:38 pm

Re: Flexi Chassis an Appreciation

Postby Russ Elliott » Fri May 19, 2017 12:11 am

Will L wrote:We feeling a bit defeatest today Russ?

I hope not. I'm merely respecting Jol's perspective, and I think we would be a poorer collective if there weren't differences and diverse preferences, whether arising from keeping with a familiar path or wanting to explore something new. The question of balancing perceivable benefits against extra effort will always be a personal one. I am a fan of CSBs, but I do not feel a need to defend them, except to say that, having put much effort into controlling longitudinal acceleration, it seems strange to me that we should not seek also to control vertical acceleration.

billbedford
Posts: 709
Joined: Tue Oct 02, 2012 2:40 pm

Re: Flexi Chassis an Appreciation

Postby billbedford » Fri May 19, 2017 12:05 pm

Jol Wilkinson wrote:I don't need reassuring. I am sure that CSB's work well.

The question is, would I get a perceivable benefit over what I do now, for the extra effort?



Maybe.

What designing for CSBs does do is force the modeller to consider the position of the CoG before cutting metal. This I consider to be a Good Thing(™) whatever method of building the frames is being contemplated. While it is true that a miss-placed CoG will produce an un-level CSB frames a similar place CoG on Flexichas type frames will produce unintended weight distribution leading to the possibility of a lowering of haulage capacity and/or a loss of stability. I don't think that either form of construction is particularly sensitive to problems when the CoG is a few millimetres adrift, but the results of the Deputy Chairman's Cup trials suggest that Flexichas chassis could masked a whole lot of CoG problems.

As for the list of CSB frame for 'problem' wheel arrangements, I don't see anything particularly difficult about any of them if modellers are willing look for new solutions, with the possible exception of the badly designed 4-60 frames.
Bill Bedford
Mousa Models
http://www.mousa.biz

proto87stores

Re: Flexi Chassis an Appreciation

Postby proto87stores » Fri May 19, 2017 6:03 pm

billbedford wrote:
Jol Wilkinson wrote:I don't need reassuring. I am sure that CSB's work well.

The question is, would I get a perceivable benefit over what I do now, for the extra effort?



Maybe.

What designing for CSBs does do is force the modeller to consider the position of the CoG before cutting metal. This I consider to be a Good Thing(™) whatever method of building the frames is being contemplated. While it is true that a miss-placed CoG will produce an un-level CSB frames a similar place CoG on Flexichas type frames will produce unintended weight distribution leading to the possibility of a lowering of haulage capacity and/or a loss of stability. I don't think that either form of construction is particularly sensitive to problems when the CoG is a few millimetres adrift, but the results of the Deputy Chairman's Cup trials suggest that Flexichas chassis could masked a whole lot of CoG problems.

By winning???

As for the list of CSB frame for 'problem' wheel arrangements, I don't see anything particularly difficult about any of them if modellers are willing look for new solutions, with the possible exception of the badly designed 4-60 frames.


Instability is a red herring in the context of equalization vs. springing.

The potential for instability you are referring to Bill, is only that possible if using 3 point support and having a c of g on the edge of the triangle formed by the body mass support points.

A correctly equalized chassis will be absolutely stable unless the c of g is outside of the rectangle formed by the four body mass support points. For the same locomotive using springing, stability has the same conditions, with the rectangle extended to the axle positions of the outermost wheels except that some wobble is now possible, and particularly so on twisted track.

Given the more limited construction options available at the time, the original Flexichas suggestions do include 3 point support as being more practical then. But I don't see any need to build quite that way today.

In the case of many locomotive kits, it is difficult to see how the fundamental c of g position can be changed very much, except by selectively adding heavy ballast asymmetrically.

Andy

billbedford
Posts: 709
Joined: Tue Oct 02, 2012 2:40 pm

Re: Flexi Chassis an Appreciation

Postby billbedford » Fri May 19, 2017 7:29 pm

proto87stores wrote:Instability is a red herring in the context of equalization vs. springing.

The potential for instability you are referring to Bill, is only that possible if using 3 point support and having a c of g on the edge of the triangle formed by the body mass support points.


But that's just what many people found. They followed Sharman and Rice and then wondered why they locos kept falling over.
Bill Bedford
Mousa Models
http://www.mousa.biz

billbedford
Posts: 709
Joined: Tue Oct 02, 2012 2:40 pm

Re: Flexi Chassis an Appreciation

Postby billbedford » Fri May 19, 2017 7:29 pm

billbedford wrote:
proto87stores wrote:Instability is a red herring in the context of equalization vs. springing.

The potential for instability you are referring to Bill, is only that possible if using 3 point support and having a c of g on the edge of the triangle formed by the body mass support points.


But that's just what many people did. They followed Sharman and Rice's instructions and then wondered why they locos kept falling over.
Bill Bedford
Mousa Models
http://www.mousa.biz

User avatar
Jol Wilkinson
Posts: 804
Joined: Mon Jul 21, 2008 7:39 pm

Re: Flexi Chassis an Appreciation

Postby Jol Wilkinson » Fri May 19, 2017 7:44 pm

billbedford wrote:
billbedford wrote:
proto87stores wrote:Instability is a red herring in the context of equalization vs. springing.

The potential for instability you are referring to Bill, is only that possible if using 3 point support and having a c of g on the edge of the triangle formed by the body mass support points.


But that's just what many people did. They followed Sharman and Rice's instructions and then wondered why they locos kept falling over.


Bill,

do you actually have evidence of that or is it just another myth put about by those who want to discredit the Flexichass concept.

Presumably you posted it twice to strengthen your argument. :)

Jol

Knuckles
Posts: 1222
Joined: Fri Nov 18, 2011 9:15 pm

Re: Flexi Chassis an Appreciation

Postby Knuckles » Fri May 19, 2017 8:35 pm

I think by 2017 it would have been obvious by now that all these systems when set up right work well for some people and preferences and when set up wrong don't. Horses for courses, trucks for sidings....


I'm finding this whole thread interesting and insightful, fly on a board style.
“He who dares not offend cannot be honest.” Thomas Paine

http://www.shapeways.com/shops/sparksho ... eationsscc
Mostly offering Loco kits & bits in 4mm.
SCC Photon Resin Prints Price list
download/file.php?id=19320

Julian Roberts
Posts: 898
Joined: Sat Jan 09, 2010 11:33 pm

Re: Flexi Chassis an Appreciation

Postby Julian Roberts » Fri May 19, 2017 8:43 pm

Jol Wilkinson wrote: Despite proclamations elsewhere that Flexichass locos are less"stable" than sprung or CSB chassis, I haven't found that a problem and would suggest that, for most of us, it is something of a red herring.


Here-here Jol.

proto87stores

Re: Flexi Chassis an Appreciation

Postby proto87stores » Fri May 19, 2017 9:26 pm

grovenor-2685 wrote:
A a well-designed etched equalized chassis can easily be less complicated, even at the largest USA wheel arrangements - e.g. 4-8-8-2 and the less common UK ones - e.g. 2-2-2 and 0-4-4

Andy, you do keep making this sort of remark, but don't present any evidence for us to compare with the complexity of Mike Sharman's flexichas book or the S4 digest. Don't bother with the 0-4-4 or 2-2-2 as they are simple cases, the complexity comes with the big ones.
Regards


Mea Culpa. Yes I do.

I have the ideas and process in my head and am slowly working along those lines while waiting for the mineral wagon test to arrive. (scheduled to arrive early next week). Waiting until I am able to show the N7 chassis running will however save me writing at least 20 long text pre- explanation posts, which I don't really have time for. Let alone perhaps the same number answering theoretical doubts, various shades of scarlet herrings, etc.

However, given that no-one else seems to be anticipating what I considered some very simple ideas, I'm now wondering if It might be sensible to first quickly file a provisional US patent, before disclosing the methods. Due to my prior career experience, I'm very aware of the factors which make manufacturing easier and cheaper, and it is possible that my product watchers at Bachmann and others might be eventually interested for their RTR features. I'll be looking into that possibility in the coming week or so.

Andy

PS. A US patent would not apply to UK producers, so no harm to The S4 Society or it's members.

billbedford
Posts: 709
Joined: Tue Oct 02, 2012 2:40 pm

Re: Flexi Chassis an Appreciation

Postby billbedford » Sat May 20, 2017 8:29 am

Jol Wilkinson wrote:do you actually have evidence of that or is it just another myth put about by those who want to discredit the Flexichass concept.


It's relatively easy to do. It just needs a fixed rear axle, a heavy white metal smoke box and extra ballast (cos more weight is better - right?) in the boiler and the CoG comes out in front of the middle axle and perilously close to the suspension point of the single beam.

Presumably you posted it twice to strengthen your argument. :)



Of course...
Bill Bedford
Mousa Models
http://www.mousa.biz

User avatar
Jol Wilkinson
Posts: 804
Joined: Mon Jul 21, 2008 7:39 pm

Re: Flexi Chassis an Appreciation

Postby Jol Wilkinson » Sat May 20, 2017 9:58 am

billbedford wrote:
Jol Wilkinson wrote:do you actually have evidence of that or is it just another myth put about by those who want to discredit the Flexichass concept.


It's relatively easy to do. It just needs a fixed rear axle, a heavy white metal smoke box and extra ballast (cos more weight is better - right?) in the boiler and the CoG comes out in front of the middle axle and perilously close to the suspension point of the single beam.

Presumably you posted it twice to strengthen your argument. :)



Of course...


That's only one example Bill, whereas you said;
"But that's just what many people did. They followed Sharman and Rice's instructions and then wondered why they locos kept falling over"

Actually, I haven't actually seen a loco "fall over" since my Hornby Dublo days. And why anyone building a loco in the way you describe, without recognising the need to balance the loco just as you even would probably do with CSB's, is most surprising.

I appreciate those who push the modelling envelope, but not everything always provides tangible benefits against the extra effort required to make it worthwhile. Why you and your fellow CSB advocates can't accept that, I don't understand.

Jol

PS We spoke some time ago about some trial 7’ driving wheels. Any progress? To show I am not a complete Luddite, I’ll build a CSB chassis for use with them if they turn up.

billbedford
Posts: 709
Joined: Tue Oct 02, 2012 2:40 pm

Re: Flexi Chassis an Appreciation

Postby billbedford » Sat May 20, 2017 10:22 am

Jol Wilkinson wrote:That's only one example Bill, whereas you said;
"But that's just what many people did. They followed Sharman and Rice's instructions and then wondered why they locos kept falling over"

Actually, I haven't actually seen a loco "fall over" since my Hornby Dublo days.


There was a example posted to this very forum in the last few months, not that I can find it now...

And why anyone building a loco in the way you describe, without recognising the need to balance the loco just as you even would probably do with CSB's, is most surprising.


Maybe I have spent more time watching modellers at work and have become a lot less sanguine than you are.

I appreciate those who push the modelling envelope, but not everything always provides tangible benefits against the extra effort required to make it worthwhile. Why you and your fellow CSB advocates can't accept that, I don't understand.


Speaking as a kit designer, I think there is a difference between things being simple because people are used to the methods of construction and simple because as much of the design work as possible has been separated from the construction. i.e. anything that increases the component count is going in the wrong direction.

PS We spoke some time ago about some trial 7’ driving wheels. Any progress? To show I am not a complete Luddite, I’ll build a CSB chassis for use with them if they turn up.


The release of the new print run of the Sharman wheel book (and the need to do a major update of the website) has prompted me to start thinking about producing wheels again. So yours should turn up soon.
Bill Bedford
Mousa Models
http://www.mousa.biz

proto87stores

Re: Flexi Chassis an Appreciation

Postby proto87stores » Sat May 20, 2017 2:40 pm

billbedford wrote:
Jol Wilkinson wrote:do you actually have evidence of that or is it just another myth put about by those who want to discredit the Flexichass concept.


It's relatively easy to do. It just needs a fixed rear axle, a heavy white metal smoke box and extra ballast (cos more weight is better - right?) in the boiler and the CoG comes out in front of the middle axle and perilously close to the suspension point of the single beam.

Presumably you posted it twice to strengthen your argument. :)



Of course...


That's why "compensation" ( a non-specific general modelling term for some up/down moveable wheels) should not be confused with "equalization" which refers to a specific means of making wheel carrying weights controlled to desired values on both models and prototypes of many types of wheeled vehicles over uneven terrain..

Andy

proto87stores

Re: Flexi Chassis an Appreciation

Postby proto87stores » Sat May 20, 2017 2:55 pm

billbedford wrote:Speaking as a kit designer, I think there is a difference between things being simple because people are used to the methods of construction and simple because as much of the design work as possible has been separated from the construction. i.e. anything that increases the component count is going in the wrong direction.


But you continue to propose Hornblocks. They fall into all your criticism categories. And several others.

Andy

billbedford
Posts: 709
Joined: Tue Oct 02, 2012 2:40 pm

Re: Flexi Chassis an Appreciation

Postby billbedford » Sat May 20, 2017 3:26 pm

proto87stores wrote:
But you continue to propose Hornblocks. They fall into all your criticism categories. And several others.



Please feel free to enumerate that way you think this would be true.
Bill Bedford
Mousa Models
http://www.mousa.biz


Return to “Guest Book”

Who is online

Users browsing this forum: No registered users and 2 guests