Soldering Brass Propellers

[Peter Morris 5Participant @petermorris5]

I have to solder some brass propeller blades to a hub which, fortunately is already slotted. Is soft (lead/tin) solder suitable or does it need to be silver solder? Any advice will be welcomed.

[Peter Morris 5Participant @petermorris5]

[Dave MilbournParticipant @davemilbourn48782]

Peter

I would personally use silver solder, although it's probably my least favourite job. That's why I buy Simon Higgins' props ready-cast! There are likely hundreds of videos on 'Tinternet showing you how to do it.
Good luck, mate.

Dave M

[Charles OatesParticipant @charlesoates31738]

Is the prop for a high speed model? If it is then silver solder is preferred as Dave says.

A propeller for a sedate model is another matter, and one of the harder varieties of soft solder will suffice. There is also the matter of what solder, if any, is holding the other blades in. mixing hard and soft solders in the same job is something worth getting a better opinion than mine on.

I always make my own props for slow models, and use a high temperature soft solder. I've never had a problem.

Chas

[Ray Wood 3Participant @raywood3]

Hi Peter,

I may have over heard discussing this at the lake this morning ! I've been thinking about making my own brass props as they are quite expensive, soft solder fillets can be created between the boss and the blades that can be fettled to decent shape. I've also thinking of an external jig to keep the blade pitch, if you need a 250watt soldering iron I have a couple, saves you from using a blow lamp

Kind Regards. Ray

[Peter Morris 5Participant @petermorris5]

Thanks to you all for your advice. Let me know when you've made that jig Ray, I might like to borrow it!!

Peter

[Charles OatesParticipant @charlesoates31738]

May I recommend an alternative to a jig, it's worked for me making around 20 propellers.. Using the slots cut into the boss, insert the blades so that they are a tight interference fit. I put a tiny bend in the root of the blades to do this. Have the boss on a short length of shaft and spin it whilst looking at it with a mark 1 eyeball! The eye is remarkably accurate at spotting any differences in the set of the blades. When happy solder the whole thing with a mini blowtorch in 1 go. Balance the prop with a couple of old Stanley knive blades set on a block and a level surface. Polish and and fit to the model.

It takes me a relaxed 30 mins or so to set, solder and balance a prop, so its time well spent.

This method is fine for general slow to medium revving props, the sort of thing a 545, 385 or 555 motor is used for. For high revving and performance, buy a professionally made one.

Chas

 

Edited By Charles Oates on 04/04/2018 23:25:19

[Peter Morris 5Participant @petermorris5]

Thanks Chas, having investigated a jig on an Australian forum which would have taken a whole engineering workshop to fabricate, I like your thinking!!

Peter

[Peter Morris 5Participant @petermorris5]

Chas

Can you let me have a specification/supplier for the 'harder variety' of soft solder that you use please?

Peter

[Charles OatesParticipant @charlesoates31738]

Hi Peter, actually I buy mine from one of many Chinese outlets that proliferate here in Spain. I first bought some expecting it to be similar to my favourite electrical solder. It wasn't, as often happens when buying stuff from outlets like this, it isn't what it purports to be, it wouldn't even melt on any of my soldering irons. Soon the penny dropped and I use it with a mini blowtorch for soldering brass, with a little flux. I recon that it must melt at about 225 degrees, as my best iron goes to just short of that.

Now I must do something I hate, trying to talk about something I'm not qualified to comment on. Solders have quite a range of mixes and melting points, I think most electrical solders melt at about 190 degrees, and I'm probably using one around 225 to 235 degrees. A quick look on Amazon shows a big range of solders including some that seem similar so that's a possibility.

I'm hoping that someone qualified to discuss solder will give you better advice, I'm a decent modeler, but no engineer.

Chas.

[Peter Morris 5Participant @petermorris5]

Hi Chas

Many thanks once again for your advice which is much appreciated.

Regards

Peter

[Eddie LancasterParticipant @eddielancaster]

Hi Peter, Try Comsol a solder paste combined with flux, melting temp. is 296 deg. Silverflo silver solder melts at 630 to 660 deg.that's a bright red in day light and needs easyflo flux. All are available from most model engineers suppliers.

Regards

Eddie.

[Peter Morris 5Participant @petermorris5]

Thanks for that information Eddie. I've ended up using a lead-free solder with a melting point around 290 deg. and, fingers crossed, it seems to have worked OK!

​Regards Peter

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