Strengthening broken struts?

[SprueMan]

From time to time, the very much annoying happens. A strut (like a wing strut) or a piece of car suspensions breaks during construction.

Usually, in the worst possible place, in the most strength demanding place.

 

How would you fix these?

 

Sometimes, a simple end to end gluing hold (by the luck of the modeling gods) but often not.

I have previously cut a groove into the part lengthwise, and inserted a new rod, or added a very thin piece of sheet styrene on one or both sides, but its often not enough, or it would be too visible.

Making a new part would also be beneficial, but it's not always possible or easy to do (like an oval part, or a part having multiple weird protrusions etc.

 

So what would you do?

[Mike]

You could always drill the two ends of the strut and join them together rather than putting a groove in it and giving yourself a filler job to do?  You'd have to be careful to make sure that they line up, but they usually end up decently strong in my experience

[SprueMan]

Ah, the problem with that, is the pieces (in my cases) are too small to insert a piece into 

[Mike]

6 minutes ago, SprueMan said:

Ah, the problem with that, is the pieces (in my cases) are too small to insert a piece into 

Hmmm.  I've got a few drills that go down to 0.3mm, and some matching rod.  No use?  If that's the case, I'd be looking at making a replacement strut.  A pain, but  logical way to fix it.

[bentwaters81tfw]

Shame Contrail, or Mike Eacock's brass 'Strutz' are no longer available. Maybe try Albion Alloys range for something usable.

[Black Knight]

I have used 0.3mm drills and wire to fix 1/72 biplane struts and 1/72 u/c legs on others. I just did the front leg on a 1/72  F-104

Sometimes a new strut needs making. John Adams did a tutorial on it

Its quite easy to do

[modelmaker]

I can't add too much to help with broken struts I'm afraid, except that once or twice I've managed, or at least 'got away with it' by using a narrow-ish strip of thin plastic card as a splint on the outside of strut, on one side. Once it's all thoroughly dry you can sand it on a piece of fine dry oxide paper, and/or carefully scrape the thin plastic card until it's almost non existent. Although it isn't structurally strong it is surprisingly more robust then just butt glueing and only visible if you know it's there. It can work in an emergency. 

 

I've made use of the very fine needles which go with my insulin pens for making internal strengthening pins, being as they are free to we diabetics, and quite thin (0.25mm). The old disposable syringes had slightly larger 0.3mm needles pre-attached which were strong enough to use as drills for jobs like biplane rigging on '72nd models or drilling holes in broken undercarriage legs/wings if they get broken off. The.25 needles are too thin. As soon as I realised I salvaged every used syringe from the sharps box and rescued the needles. 

Edited October 21, 2022 by modelmaker
Missed a word out!

[SprueMan]

16 hours ago, Mike said:

Hmmm.  I've got a few drills that go down to 0.3mm, and some matching rod.  No use?  If that's the case, I'd be looking at making a replacement strut.  A pain, but  logical way to fix it.

Yes, I have them, but a 1.2mm strut and a 0.3mm drill is too small for my wobbly fingers.
Replacement, or the other suggestions here are the way to go... Me thinks.

[Paul Thompson]

18 hours ago, SprueMan said:

Yes, I have them, but a 1.2mm strut and a 0.3mm drill is too small for my wobbly fingers.
Replacement, or the other suggestions here are the way to go... Me thinks.

I used to think the same, but starting the hole with the tip of a no.11p scalpel blade helps. Sharper than pin. Just position it carefully and give a slight twist so you have a circular micro dint to stick the drill end into. Very hard to do, but possible. Hey, I never said it would be fun.

The other thing that helps is to practise by drilling out progressively thinner bits of stretched sprue, where at least the raw material is free.

 

Paul.

[modelmaker]

I have all sorts of bits of old hypodermic needles, bits of brass tube, the needles from the little bottles I once used to buy to refill printer cartridges and more stuff besides. If I want drill a hole in sprue,  broken circular struts, or other circular parts I first find a short length of tube which fits snugly (if I can) over the part I want to drill. I then get out the micro drills and find the largest one I can to fit inside the tube. If you're careful this will drill a little dimple into the tube which you can use as a centre when drilling the piece. It usually helps. 

[Paul Thompson]

4 minutes ago, modelmaker said:

I have all sorts of bits of old hypodermic needles, bits of brass tube, the needles from the little bottles I once used to buy to refill printer cartridges and more stuff besides. If I want drill a hole in sprue,  broken circular struts, or other circular parts I first find a short length of tube which fits snugly (if I can) over the part I want to drill. I then get out the micro drills and find the largest one I can to fit inside the tube. If you're careful this will drill a little dimple into the tube which you can use as a centre when drilling the piece. It usually helps. 

I never thought of that (and yet, I'm from Birmingham .............. how did I miss it?)  I'll be giving that a try come the next mishap.

 

Paul.

[modelmaker]

Finest folk in the world, modelling Brummies. That's Brummies who make models, not Brummies on catwalks, although I suppose there might be some overlap.....

 

The hypo Idea can help because I'm terrible at centering using a needle. 

[Black Knight]

One other thought on making new struts

If you heat stretch sprue, to a thinness you require, after its hard very carefully squash it with a pair of pliers., it will go from round to oval section

I have some special pliers I use for the metal fittings in my leather and jewellery making. One pair has perfectly smooth jaws which I use to do this

I made the cabane struts on this Airfix 1/72 Bristol Bulldog that way

 

[Rob de Bie]

On 10/21/2022 at 4:47 PM, SprueMan said:

Yes, I have them, but a 1.2mm strut and a 0.3mm drill is too small for my wobbly fingers.
Replacement, or the other suggestions here are the way to go... Me thinks.

 

I once recast a helicopter landing gear strut with a brass wire inside. That worked beautifully. Left to right: broken but reglued original part, straight resin copy, resin copy with wire insert, wire insert.

 

 

Rob

[TallBlondJohn]

On 22/10/2022 at 18:53, Black Knight said:

One other thought on making new struts

Of you heat stretch sprue, to a thinness you require, after its hard very carefully squash it with a pair of pliers., it will go from round to oval section

I have some special pliers I use for the metal fittings in my leather and jewellery making. One pair has perfectly smooth jaws which I use to do this

I made the cabane struts on this Airfix 1/72 Bristol Bulldog that way

 

Oooh that's worth a try, I have an Airfix Bulldog and just the right pliers too. I've made long oval struts (e.g. Supermarine S6B) by supergluing brass rods of various diameters together, then filling the gaps in with more superglue and talc, then sanding the lot. Bit its a lot of faff and invites superglue calamity. If you try it, clean and sand the brass rods a bit first to make sure they are grease free and grippy.

[Black Knight]

. . . . . and another idea

Round florists wire. Its soft iron. If you very lightly hammer it on an anvil you can make it go from round to oval. 

But you are very limited on the size of strut you can make

[Rob de Bie]

For simple struts, Albion micro tubing is very useful. You can flatten it slightly, like in the first photo. If you go too far, it gets an '8' cross section. I would insert some stretched sprue now, to avoid that.

 

 

 

Rob