Home Grown PZIII/Stug rear idlers

[Gigantohawk]

Pete(971wright) and myself have been trying to find a DIY solution to making rear idlers to the correct diameter for these tanks. In such a way as to make them usable and durable.
I have managed with HL bits to fashion one out of plastic but I'm concerned with the overall strength of this .
We've been discussing the possibility of casting our own out of white metal and working through problems we would encounter with producing these in such a way. However after giving it some more thought I just wondered if this would work.
Using metal idlers and giving them  the same treatment as the plastic one in the photo it should be possible to "silver solder" metal turned hoops on to the modifyed idlers ending up with a strong and scale diameter wheel as shown in the second photo.
I know you've seen the pic's before. I just wondered if the idea sounded feasable.

What do you think guys.

Nick.

I hope the pic's came through at a usable size this time !.

[tiger205]

hi nick, i think youre idea of giving the metal idlers the same treatment as the plastic ones is a good sound idea i cant see a reason why it wouldnt work, if youre good at soldering, but if you can cast them in metal then that would be the best option, may be you could take a mould from the plastic ones?

                Tony

[grompix]

Nice idea Nick but I suspect you won't be able to silver-solder the die-cast metal the idlers are made of. Die-cast stuff is made from aluminium and zinc and will not take solder (even lead/soft solder). I think your best bet is to make a silicon-rubber mold and cast the idlers from white metal (tin/lead). If you get a white metal with a high tin content I'm sure it will be rigid enough to act as a good idler- You might need to put a brass or bronze sleeve in the idler hub to reduce wear though (or a ball-race of course).

Hope this helps
Cheers
Chris

[971wright]

Hi Guys I can get my hands on wheel balance wheights lots of them I would think this would melt down pretty easy and should give a good quality casting and still be strong ,If I can get some RTV which has a good tolarance to heat they use it as fire retardant on aircraft engines ,we can make a mould from this then the only problem would be when casting do we need a centrifuge to aid casting.

        regards pete

[grompix]

Yes that should do it Pete. The idler is a simple shape so you'll probably get away with a two part drop mold so long as the pouring hole is quite substantial to allow the weight of the metal to fill all the nooks and crannies. Cutting narrow air-lines between the spokes should help with the casting too.

Regards
Chris

[Gigantohawk]

Gentlemen,
Thanks for all of your replies. It seems clear that casting, if a bit complicated, is the best option. However I'm still trying to work through the "silver solder" option. May I call on you all to suggest the best method to solder aluminium to aluminium.

Thanks in anticipation,

Nick.

[Plastic scouser]

wouldn't it be better to get an outside company to cast up the idlers in zinc or whatever they use?

You could get a list of everyone whos interested and work out cost per set from the casters estimate as it is usually cheaper the more you order.  Just something else to throw in the mix ::)

I myself would be in for two sets.

Cheers Ian

[grompix]

Unfortunately there isn't any easy way to solder aluminium Nick. It can be welded but that's a highly skilled job requiring specialist equipment. For the home workshop the only solutions to joining aluminium are glueing, riveting or bolting - none of which fit the bill for your requirements I think.
I think casting in a tin-based white metal alloy is your way to go and for that you need a silicon rubber that could withstand high temperatures (RTF is a good one that Pete suggested). You could make plaster molds but they are only good for one or two casts.
It is possible to do your own die-casts of course but you will need a furnace capable of heating the zinc/aluminium metal to a high enough temperature (much higher than tin-based  white metal casting) and the mold must be a sand-mold or a specially made multi-part metal one (hugely expensive to do).

Alec Taranti is  good place to find out about mold making and casting. I get all my casting supplies from them. They have good instructional leaflets too.
http://www.tiranti.co.uk/

Hope this helps
Chris  

[tiger205]

hi gigantohawk, another option for welding ally, is lumiweld rods, all you need is a butane blow lamp, its easy to use, and you dont need expensive welding gear, http://www.frost.co.uk/item_Detail.asp? ... ostSubcat= this link takes you to "frost" a car resto'  site, its certainly worth a look

              Tony

[971wright]

Aluminium is the hardest thing to weld ask any welder it will if not very careful just turn into a blob of moulten metal right infront of your eyes .white metals are even worse to do because of low melting point.its likwe trying to weld ice you put heat on it and it dosnt change colour so its hard to tell when you are reaching melting point ,It just turns to a very hot liquid .

          regards pete