Re: Suspension [was; Re: Boxpok driver model preview]
Ken It's partly because of the flammability problem that just packing the leaf springs works so well. You cut the leaves from the thinest spring stock you have and then cut the ends off every other leaf. (This all takes some experimentation on the specific model). That's one reason it's such a fiddly job. That's a really good idea of yours to use the dummy leaf spring as the equalizer. Solves all the problems and is relatively easy to construct. Victor Lacy - Original Message - From: "XXYZ" <[EMAIL PROTECTED]> To: "Multiple recipients of sslivesteam" <[EMAIL PROTECTED]> Sent: Monday, October 28, 2002 7:02 PM Subject: RE: Suspension [was; Re: Boxpok driver model preview] > There is a great article in this quarters G1MRA newsletter about model leaf > springs. The author is making working model leaf springs from a stack of > thin plastic sheet (transparency film?) and also another style from a music > wire encased in a flexible silicone casting. It seems that the modulus of > elasticity is the problem and most metals are too "stiff" when scaled > properly. Both of these solutions are really creative but are more > appropriate for rolling stock that isn't subject to the heat and flammable > surroundings of live steam locos. > > Last month the newsletter feature an article about the construction of an > electric tank locomotive that had working coil springs hidden inside of the > cosmetic leaf spring castings, Cool! > > In a nutshell: making the leaves hollow wouldn't change the flex of the > spring much as the amount of flex (deflection of a beam) is determined > greatly by the outside dimensions (I'm simplifying greatly) of the cross > section. Removing material from the center reduces weight but doesn't have > as great of an effect on flexibility as does removing the material from the > outside. This is shown very nicely in I-beams. (think of an I-beam as a > square section with one side removed and the other moved to center to > balance) > > Ken
Re: Suspension [was; Re: Boxpok driver model preview]
That's what I've been planning for some sparkies I'm modifying but I thought I'd look into using springs while I was at it. I suppose it'd work ok if you just built the springs with the intention that they wouldn't do the job anyways. :] So far I've only made a Bachmann 10 wheeler such that the front axle can rock and stay on the rails. Those things are actually only 4-4-0's anyway. ;] That middle set is like some odd jackshaft arrangement... Roundhouse steamers are built the same way and I've given some thought to doing the same with mine. However, I currently don't feel I have the experience or machinery to do the job right. For that reason I'm sticking to plastic for all my suspension experiments... I'll play with metal when I get (at least) a drill-press. ;] Trot, the semi-prototypical, fox... On Mon, 28 Oct 2002, VR Bass wrote: > All those drawbacks of scaling springs is why a lot of modelers prefer > equalization without springing. This is done in scales as small as H0 and it's > not really that difficult from what I've seen (I haven't done it myself yet). > > regards, > -vance- > > Vance Bass > Albuquerque, New Mexico, USA > Small-scale live steam resources: http://www.nmia.com/~vrbass /\_/\TrotFox\ Always remember, ( o o ) AKA Landon Solomon \ "There is a >\./< [EMAIL PROTECTED] \ third alternative."
Re: Suspension [was; Re: Boxpok driver model preview]
Trot wrote: >This is something I've been curious about for a while now. Why are real springs too strong? Are our locos not heavy enough or is it a problem with the volume of metal used in the springs? and Jim correctly responded: >The problem is that the weight of a model of a loco varies as the cube of >the scale, so a 1:10 scale model of a 100 ton model has a scale weight of >1:1000 of the original weight, ie 1/10 of a ton = 224 pounds. The spring >rate does not scale at the same rate, so the springs end up too stiff. To go just a step farther. Elastic properties generally go by the cross-sectional area of the material, which varies as the square of the dimension. In Jim's example, the springs have a cross-sectional area of 1:10 squared or 1:100 as great as the original, but the model weighs only 1:1000 of the original weight. Therefore, the scaled springs are in effect 10 times less yielding than the originals, and have to be made of other material or of smaller size. It is this effect that makes ants so proportionally strong and also limits the size of land dwelling animals to roughly the size of a big dinosaur and even puts a limit on how high mountains can be (but that's REALLY off the track). David Krause
Re: Suspension [was; Re: Boxpok driver model preview]
All those drawbacks of scaling springs is why a lot of modelers prefer equalization without springing. This is done in scales as small as H0 and it's not really that difficult from what I've seen (I haven't done it myself yet). regards, -vance- Vance Bass Albuquerque, New Mexico, USA Small-scale live steam resources: http://www.nmia.com/~vrbass
Re: Suspension [was; Re: Boxpok driver model preview]
Hi Trot. One of the dodges used in the smaller ride on scales is to make the spring leaves out of Tufnol - the resin bonded paper or fibreglass cloth insulating material (SRBP or SRBC) as used for the backing of printed ciruit boards. This is available as quite thin (down to1/32" or less) sheet. This is cut into strips the width of the spring leaves, and bent round a suitable curved former (aka coffe can!) and heated until it discolours. This gives a permanent curved set to the leaves. These Tufnol leaves can be interleaved with steel ones if needed to get the spring rate right. The problem is that the weight of a model of a loco varies as the cube of the scale, so a 1:10 scale model of a 100 ton model has a scale weight of 1:1000 of the original weight, ie 1/10 of a ton = 224 pounds. The spring rate does not scale at the same rate, so the springs end up too stiff. We complicate the issue because since models do not duplicate the construction of the prototype, their actual weight is wrong anyway! Jim Gregg. At 03:44 PM 10/28/02 -0500, you wrote: This is something I've been curious about for a while now. Why are real springs too strong? Are our locos not heavy enough or is it a problem with the volume of metal used in the springs? Could real leaves be made with hollow sections? I know it'd be a lot of work but this is just for the sake of understanding... Is there not some lighter metal that could be used, or do they get too malleable at the 'correct' flex range so that they'd be easily bent? Curious foxes want to know! Trot, the fox who's not a rivit counter, really..! On Mon, 28 Oct 2002, Jeanne Baer wrote: > I would definitely spring the drivers. Even in gauge 1 the engine will run > much happier with springing. > > Equalizing is something else again. It's complex and fiddly (especially if > you equalize across the chassis as well as on each side) and won't get you > much for your trouble compared to the gains from simple springing. Also, you > cannot get the exact prototypical look using leaf springs. If you copy the > full size exactly, the springs are too stiff. To correct that you can go > undersize with the leaves and pack the stack. But then you've lost "the > look". > > Dummy leaf springs with concealed coils doing the actual work are a pretty > good compromise. > > If you want something good for beginners, I would not use SS for the > drivers. It can be too frustrating to machine. > > Also, if I hadn't done quite a bit of casting I would stay with aluminum and > zinc (or other low temp white metals). These, however, need a tire shrunken > on and so another job. Only if I wanted a really big project would I try > brass and cast iron rather than have them commercially done. > > Victor Lacy /\_/\TrotFox\ Always remember, ( o o ) AKA Landon Solomon \ "There is a >\./< [EMAIL PROTECTED] \ third alternative."
RE: Suspension [was; Re: Boxpok driver model preview]
There is a great article in this quarters G1MRA newsletter about model leaf springs. The author is making working model leaf springs from a stack of thin plastic sheet (transparency film?) and also another style from a music wire encased in a flexible silicone casting. It seems that the modulus of elasticity is the problem and most metals are too "stiff" when scaled properly. Both of these solutions are really creative but are more appropriate for rolling stock that isn't subject to the heat and flammable surroundings of live steam locos. Last month the newsletter feature an article about the construction of an electric tank locomotive that had working coil springs hidden inside of the cosmetic leaf spring castings, Cool! In a nutshell: making the leaves hollow wouldn't change the flex of the spring much as the amount of flex (deflection of a beam) is determined greatly by the outside dimensions (I'm simplifying greatly) of the cross section. Removing material from the center reduces weight but doesn't have as great of an effect on flexibility as does removing the material from the outside. This is shown very nicely in I-beams. (think of an I-beam as a square section with one side removed and the other moved to center to balance) Ken > > This is something I've been curious about for a while now. Why are real > springs too strong? Are our locos not heavy enough or is it a problem > with the volume of metal used in the springs? Could real leaves be made > with hollow sections? I know it'd be a lot of work but this is just for > the sake of understanding... > > Is there not some lighter metal that could be used, or do they get too > malleable at the 'correct' flex range so that they'd be easily bent? > > Curious foxes want to know! > > Trot, the fox who's not a rivit counter, really..! > > On Mon, 28 Oct 2002, Jeanne Baer wrote: > > > I would definitely spring the drivers. Even in gauge 1 the > engine will run > > much happier with springing. > > > > Equalizing is something else again. It's complex and fiddly > (especially if > > you equalize across the chassis as well as on each side) and > won't get you > > much for your trouble compared to the gains from simple > springing. Also, you > > cannot get the exact prototypical look using leaf springs. If > you copy the > > full size exactly, the springs are too stiff. To correct that you can go > > undersize with the leaves and pack the stack. But then you've lost "the > > look". > > > > Dummy leaf springs with concealed coils doing the actual work > are a pretty > > good compromise. > > > > If you want something good for beginners, I would not use SS for the > > drivers. It can be too frustrating to machine. > > > > Also, if I hadn't done quite a bit of casting I would stay with > aluminum and > > zinc (or other low temp white metals). These, however, need a > tire shrunken > > on and so another job. Only if I wanted a really big project would I try > > brass and cast iron rather than have them commercially done. > > > > Victor Lacy > > > /\_/\TrotFox\ Always remember, > ( o o ) AKA Landon Solomon \ "There is a > >\./< [EMAIL PROTECTED] \ third alternative." > >
