Trying to scratchbuild a 56’ gallows type turntable in HO and found a metal casting of the lazy susan type undercarriage which I would like to copy.
Bought a book off Amazon on casting metal and rubber parts ( W.A. Cannon 2nd Edition ) and quickly came to the conclusion that I would prefer NOT to be working with molten metals if at all possible.
Is resin a viable alternative … undercarriage does NOT have to be metal - just solid !!! The undercarriage consists of a 2" lazy susan cast in two pieces as well as 12 very small ( 1/8" ) wheels.
If any of you have experience with resins, can it replace metal castings, what are the strengths and weaknesses of the approach and where can I get info on how to make the molds, castings and buy supplies, etc.
Thanx in advance for helping a newbie …
There are books and kits that cover resin casting.
I assume you need operating parts and I don’t see that working. Resin is soft (relative to metal), castings are not perfect, I am not sure how machinable they would be. I think it would work for a display model, but not an operating one.
Yes, I need what you call operating parts … the lazy susan undercarriage must, of course, rotate from one track to the next - not much stress but it is movement.
So there are ZERO alternatives to casting with molten metals ???
aluminite has info; pictures on their website, as does micromark’s; believe bragdon also makes it
there are many variations of resin casting; from flexible rubber to industrial strength that takes a long time to set and accurate measurements
casting advantage is weight, primarily
It depends on what you want the resin/plastic to do. Walthers, CV and others’ turntables and bridges are made of plastic and work fine. Most of them are pressure-injection moulded plastic not hand cast resin/plastic.
The big issues are which type of resin you opt for and quality control. How much mould rubber and resin are you prepared to waste geting the job right? (As noted in a recent thread resin can contract slighlty in the processes - so a pattern needs to be slightly over-sized).{Or cheat, make your patterns to size, reckon that the part will be fractionally small and build the larger object that the casting goes in around the shrinkage… so, if the wheel comes out a few thousandths small just allow for this in the ride height of the table as you build it rather than building the table precisely and then having the wheel not fit}.{This is what engineering solutions do in most of the real world… unless they are dealing with pressure(s), flame(s) or other similar stuff… which is why these things are so expensive}.
Resins don’t usually conduct electricity… so, if a lazy Susan is what I think it is you wouldn’t be able to use the wheels to pick up power from a rail to supply a motor… or do any other eletrical job like indexing.
Cast metals also vary considerably in strength, particularly friability. The reason we use steel far more than iron is that the molecular structure of irn makes it prone to fracture under several conditions and it becomes brittle with age. Steel is a more epensive to produce but more stable solution that lasts longer. (Not suggesting you cast in steel [swg]).
BE WARNED some resins generate heat while curing - even in quite small quantities.
[8D]
(Oops! Did I advertise Walthers or CV? [:O][:-,]
If you could post some pictures it would help us to see what it is you are trying to build. I think I have an idea of what it is but I would need to see a picture to be sure. If you want to cast a copy of the metal part please keep in mind that the resin will not be as strong as the metal parts in the same thickness. If you can not use the original part you mentioned you will have to build a master. If you only need one part then I would suggest just scratch building the part from styrene or if you are realy ambitious out of brass. I would also caution you on the cost to do this complicated of a project as your first attempt at casting. I would suspect the by time you got a satisfactory part the cost will have risen to the price of a comercialy available kit. If you are still interested in doing this some of the suppliers I use for my business are http://www.bjbenterprises.com/ http://www.liquidplasticsolutions.com/synairproducts.htm http://www.smooth-on.com/
Dan Pikulski
www.DansResinCasting.com
Pix, as requested.
The two 2" washer type halves go together to make the lazy susan mechanism under the turntable of th… the 12 little wheels in the right side half go in the holes of the assembled mechanism and run on rails. The 4 VERY small wheels in the left side half make a ‘2-wheeled truck’ at each end of the turntable and run on rails.
These are the pieces I want to cast … no strength is required - just solid, hard parts.
Any help is appreciated …
Can’t figure out how to insert the photbucket pix in here ???
If you send an email to ed.ducey@gmail.com, I will send you the pix of the parts I’m trying to cast in resin - if dooable !!!
Sorry … Ed
Many years ago there was an article about using Cerro-bend (Produced by the Cerro de Pasco Corp.) for low-temperature metal casting. The stuff could be melted in the top half of a double boiler! I believe it’s the same material used in the fusible links of automatic sprinkler systems.
Not all metal casting involves extreme temperatures or cascades of flying sparks.
Chuck (modeling Central Japan in September, 1964)
I hope you don’t mind, I took the liberty of posting your pics for you. The rings can be cast fairly easily. Are these parts from a kit? The small wheels will be a bit harder to get right and will definatly need a metal axle as a cast one will not hold up.
Thanx, Dan, for figuring out how to post my pix … I feel kinda dumb !!!
Yes, the parts are from a Sequoia TT kit which I want to copy.
Might be able to do the wheels out of styrene but you think that a standard resin would work for the bigger parts.
Again, thanx … Ed
Working w/Resin is relatively easy but is timeconuming. The mold takes about 2-4 hours to set up. I use Alumilite quite a bit when making castings but, be prepared for a failure rate of around 50%-75%. I usually make 4-5 attempts before I get an acceptable cast. When I mean acceptable, there are no air bubbles. The smaller the cast, the more of a problem air bubbles present. MR’s cousin magazine FineScaleModeler had an article on making a mold and casting. I would recommend looking for the article at www.finescalemodeler.com
Ch