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ThunderDragonCy

ABS body damage - help/advice on how to repair?

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Packed the Grasshopper3 in my bag on a trip to the local park today in the hope of getting a quick blast on the small bit of astro they have there. Had long since assumed the grass would be too long/wet/full of dog crap to be any good for running the buggy. How wrong I was! Grass was short and bumpy and mercifully dog crap free, and I had a blast on my first proper run on grass. However, some recent enthusiastic driving/crashes plus learning to drive on grass = grip roll central = cracked body. Oops:

Oops. Grip rolling on grass not so good for 25 year old body shell!

I don't have any old/spare bodyshells with off cuts or anything. Anyone got any good suggestions what to use to fix this? I'm thinking just glue a small sheet of plastic to the underside of the split and re-drill the mounting hole, but I don't know where to source appropriate material.

Thanks.

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I fixed one of mine ABS shells with fibreglass matting and resin.  Has really held together well.  You could use plasticard to fix it as youv'e suggested, but I dunno how much success you'll get in terms of strength.

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Nice one. Thanks for the knowledge. Order a bit of 3mm plasticard off ebay. I'll give that a go. Be a shape write this shell off. I'm rather fond of it.

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Go to hobbyshop or anywhere that sells Evergreen styrene sheets (model train places especially), buy a few handy packs of sheeting of various thickness also some square rods etc. 

And a bottle of styrene cement. 

the cement welds styrene to styrene not just 'glue' it together, it becomes one solid hunk. 

Butt weld your broken off bit to where it should be, then weld on a reinforcement patch underneath.

 

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3 minutes ago, ThunderDragonCy said:

Nice one. Thanks for the knowledge. Order a bit of 3mm plasticard off ebay. I'll give that a go. Be a shape write this shell off. I'm rather fond of it.

3mm is plenty thick :mellow:

i generally use more of 0.5mm & 1.0mm

this thin I can cut with scissors, don't need risking a knife :ph34r:

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Went on the conservative side. The shell is 2mm thick in that area and the repair is unlikely to the stronger than the original, which i've already broken!

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Au contraire mon ami :)

When you start playing around with styrene, you'll find the thinner flexy sheets are much more useful as you can LAYER it up, weld each layer on progressively and clamp it down as you go - you can make some fantastic compound curves! (It's like working with prepreg plaster bandages or sheetpaper mâché)

Whereas if you've only got stock of thick sheets, all you've got is a plank :rolleyes: if you try to clamp it under your broken nose, it'll likely force the buttjointed piece flat and ruin the original curve.

Planks are useful for foundation (build your own interior) or making shelves for ESC, RX etc.

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What about fixing lexan? One of my body mounts sheared clear through my new Lexan Lunchbox body on the first run out... Super glue didn't help much

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22 minutes ago, Munchbox said:

What about fixing lexan? One of my body mounts sheared clear through my new Lexan Lunchbox body on the first run out... Super glue didn't help much

nah lexan is unfixable... by my books it's a use-once throwaway item :mellow:

Superglue won't stick (chemically CA needs surface moisture to bond properly, that's why it glues your skin so well!!), epoxy won't stick etc etc. CA is also very brittle and it won't flex with the lexan.

Some do amazing lexan repairs with fibreglassing etc but IMHO it's only good for shelf display, it can't be run like an original whole lexan shell like it was before.

Your best bet to stick anything to lexan is with a flexy mastic like ShoeGoo or Selleys AllClear. It's never a permanent bond but will hang around long enough to get enough value... but when patching on the inside pray that your paint has a good grip, as it might pull the paint off. 

Better bet is to glue a patch on the outside as well as inside.

I use lexan offcuts (wheelwell bits especially handy) or flat bits of plastic packaging... waste not want not.

 

Btw lexan "tears" and it'll tear easiest from every weak point you've created. If your post hole isn't nicely smooth that's a major weak point! I cut holes by hand with a reamer as powerdrills can force fractures; also for the rough runners I heat the cut edge to melt it slightly... used to use soldering iron, now just a lighter flame.

For really rough runners (SCT!) might as well patch the holes *before* they tear.

 

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5 hours ago, WillyChang said:

Au contraire mon ami :)

When you start playing around with styrene, you'll find the thinner flexy sheets are much more useful as you can LAYER it up, weld each layer on progressively and clamp it down as you go - you can make some fantastic compound curves! (It's like working with prepreg plaster bandages or sheetpaper mâché)

Whereas if you've only got stock of thick sheets, all you've got is a plank :rolleyes: if you try to clamp it under your broken nose, it'll likely force the buttjointed piece flat and ruin the original curve.

Planks are useful for foundation (build your own interior) or making shelves for ESC, RX etc.

OK. I'm still learning. Sample set of 0.5, 0.75 and 1mm on it's way too!

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You can patch/glue lexan with silicon sealant. A high quality silicon sealant is a very strong adhesive (eg Dow Corning Clear) and will stick a lexan patch to the under side plus act as reinforcement. Dries clear and gives you a decent working time.

You can stick polished porcelain tile surfaces to each other with that method as an example of how efficient it can be where normal glues and bonds fail.

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I hadn't thought of silicone.. I'll give that a try. I did try some ca glue and it worked fine under light load but my first big rollover tore through again..

I had no luck trying to back the holes with extra lexan either.. sat for 5 minutes holding the piece down and it still came right off.

 

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On 2/4/2017 at 5:35 PM, ThunderDragonCy said:

 

Oops. Grip rolling on grass not so good for 25 year old body shell!

I don't have any old/spare bodyshells with off cuts or anything. Anyone got any good suggestions what to use to fix this? I'm thinking just glue a small sheet of plastic to the underside of the split and re-drill the mounting hole, but I don't know where to source appropriate material.

Thanks.

Do this:

Go in your local model shop and buy an ABS sheet. They are on sale in the hobby shops to make train dioramas. In Italy they are produced by Evergreen and sold in packages of sheets with different thickness.
Buy a 2 mm thick  (or more) sheet. Then, buy the Tamiya ABS glue, a cyano glue, some sanding paper and a good sharp cutter.
Then, if you have not yet, buy a couple of plastic clamps for the hobby. A couple of wood clamps (the ones to keep the wet clothes on the wires to dry) of your mother will be good anyway.

Once you are at home, cut a piece of ABS sheet that can be big enough to stay under both broken parts.

Then, with the cutter, make several X-shaped scratches under the broken parts and onto the ABS piece.
Once done, brush the ABS glue under the body, over the scratches, and place the ABS piece with the X shaped scratches against the glue. Clamp the two parts together with the clamps. Keep in mind that half of the ABS piece must exit from the body. The Tamiya ABS glue will melt the two ABS parts (the body and the sheet) and will unite them forever. The glue needs a couple of hours to dry.
Once dried, brush again the glue on the X scratches of the ABS sheet that exits from the body, place the broken piece of the nose and clamp it again and wait. Be careful to unite the two broken parts of the body as close as possible.
Once the glue is dry you can release the clamps. Now the nose of your body is in place again. More thick is the plate under, more strong is the front end of the body.
Once the two parts are united you will see the line of the breakage. Fill the line with the cyano glue. Just a little bit of cyano. When the cyano glue dries, make it again and wait. Do this operation until the line is filled up and the glue makes a sort of protrusion over the body surface. You used the cyano like a putty filler with the difference that the cyano will help the parts to stay united. The cyano will also stay firmly in place and will not remove or crumble away like the putty. At the end, the cyano is stronger and you can work it better than the putty.
Now you can sand the cyano protrusion with the cutter and the sand paper. If you will be able to do this work in the right way you will have a perfectly flat and smooth surface. Now you can drill a new hole for the body post, give the primer and the paint again.

 

Max

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You can dissolve ABS shavings (trust me you'll have endless supply of chips once you get ABS crafting) into a old halfused bottle of ABS cement to make a filler.

Filling with 'like' material is better than CA, it's easier to sand level. Cured CA is harder than ABS and harder to sand level to the surrounding area.

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Thanks so much for the detailed procedures and tips guys. I'lI let you know how it goes.

Slightly related: I have figures out why it failed. The body sits on the suspension mount lugs just behind the body mount and then isn't supported behind that because it stands clear so every time the car landed on its roof there was a big bending moment across the body mount. I would like to put some fairly firm foam under the body behind the suspension towers so the foam bridges the gap to the chassis and supports the area to spread impact loads. Anyone got any suggestions on foam to use? Moto foam is probably not dense enough. Thoughts?

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yeah go to your local foam rubber depot and get some closed cell foam, usually comes in various grades (Shore) of stiffness

or if you don't have one in your town, there's always granny's gardening kneeling pad (hardware store) or a pair of flipflops (Haviana store?)

 

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