JB Weld

[Ramon WilsonParticipant @ramonwilson3]

Hi Guys, Thought this might be of interest to some

I have long been an advocate of using JB Weld as an aid in model engineering. It is an epoxy based product that is readily available at reasonable cost. It's advertised virtues are that it has a high tensile strength listed as 5020 psi and more importantly will retain that strength under fairly high temperatures – up to 550F. There may be other products that are better – i.e. stronger but whether they have the same temperature resistance is not known. I believe it's combination of the two – at it's cost – makes it a very viable addition to any model engineers workshop.

I first began to use it on silencers for glow motors in control line flying. Dubious of it's claims at first I soon became aware of it's capabilities such that all fasteners were done away with. A glow motor can get very hot indeed at the point of exhaust but the JBW withstood this without failure and so began a journey where it's use became more and more frequent. On the last engine made it was used extensively for pipework fittings.

When I described this potential use on this particular build, it's purpose, quite understandably was questioned from a safety point of view and it made me realise that whilst I had every confidence in it's use as intended I had nothing to base that confidence on save it's previous use.

I was making the condenser at the time and the flanges for the pipework were to be simply JB'd into place. The question arose in my mind that despite the low pressures that would be involved in this item (no steam so no vacuum) I didn't actually know save faith!

I made a test piece up for the three flanges – identical to those for the model in shape size and location

The flanges were JB'd in place in the same manner as would be used

Once cured the fillets were filed to shape as per the final item

This was left for a few days to fully cure and then pressure tested. It was taken to the limit of the gauge 300psi and held for 20 plus mins or so. There was no trace of water on the blue paper.

This was then repeated but this time with the test piece submerged in constantly boiling water at the same pressure and time. No loss of pressure and no detriment to the JBW.

The part after the boiling water test. No evidence of the JB deteriorating

I then made a simple fitting up. 8 mm pipe and elbow

These were JB'd together and again left to cure

This too was pressure tested to the same pressure/time/boiling water without failure.

I'm no academic – I realise these tests aren't scientific but they served to satisfy to me any doubt that the product is fit for purpose for the application I intended it for.

I have described it's latest use on the Marine Condensing thread but thought it may be of an interest to a wider audience than that possibly attracts

Hope that's the case -Tug

 

 

Edited By Ramon Wilson on 16/03/2021 11:49:59

Edited By Ramon Wilson on 16/03/2021 11:55:31

[Ramon WilsonParticipant @ramonwilson3]

Using JB Weld in model projects

[Oily RagParticipant @oilyrag]

Ramon,

I can vouch for the high pressure and temperature qualities of JB Weld, probably only surpassed by Devcon Titanium epoxy for strength and temperature resistance. We used JB Weld extensively for 'instrumentation' purposes in development engines and even on one occasion to repair a cylinder bore which had a 'Nikasil' flaw in its bore (the Nikasil had, not surprisingly, failed to adhere to a 'flux zit' in the aluminium parent metal bore – we repaired it with JB Weld and dressed it ) we ran the engine for over 50 hours without it 'detaching!

Previously I have known complete inlet manifold systems to be constructed from Devcon by sculpting it around plasticene.

Martin

[derek hall 1Participant @derekhall1]

Wow thats really interesting Tug,

I have never used JB Weld and in fact never heard of it until it was mentioned in here.

I understand that it can be filed but is it something that can be machined as well?

Kind regards

Derek

[Jim NicParticipant @jimnic]

Thanks for that Ramon. I have used JB in the past and have had no complaints regarding its strength. For my current model stationary steam engine which (like all my engines) will run only on air, I intend to fabricate the cylinder. I have been toying with the choice of using either JB or silver solder to attach top and bottom flanges and a steam chest to the cylinder body. Your results have convinced me, JB it will be.

As an aside, in a previous life I spent a little time investigating adhesive use in non critical aircraft structural repairs using a number of different types. It was found that usually with epoxy resins the best bond was formed if the adhesive was set using a raised temperature and I now always do this where possible when using, mostly, Araldite. High temperatures are not required, placing on a domestic central heating radiator for a few hours gives benefit.

Jim

[colin vercoeParticipant @colinvercoe57719]

I Used a similar product Plastic Padding last year on a hot air pipe from a blower and it still there and working fine, outside in the sunshine.

[Phil H1Participant @philh196021]

Tug,

This is really interesting and I will be searching for uses. Please can you clarify which of the two packs you used for these tests and or would you expect the same or similar results from either of the packs?

Phil H

[Jon LawesParticipant @jonlawes51698]

Thanks for these tests Ramon, I'm very impressed. Really useful findings.

Jon

[JasonBModerator @jasonb]

The two packs that Ramon shows are actually the same product, red and black tubes, think the blue card is the Euro safety packaging. I usually go for the one on the left to be sure

Don't use the kwik or marine versions as they are not as strong and don't take the temperatures of the "original formula"

Edited By JasonB on 16/03/2021 16:29:43

[Bill PhinnParticipant @billphinn90025]

Am I the only one whose monitor shows Ramon's mixed JB Weld as a brownish mud colour? The standard stuff I've used has always been grey.

[Ramon WilsonParticipant @ramonwilson3]

Hi Guys, good to see the interest in this.

Yes the two packs are the same pre and post packaging. As Jason says Phil, the standard version is the one to use because of the reasons he states.

Bill (Phinn) the colour in the image is not as it is in reality – must be the lighting in the workshop. It is as you say a dark grey once correctly mixed. Based on something I once heard relayed from Ceiby Geigy on mixing Araldite I always make sure it is fully homogenised with no sign of any whiteness of the hardener or streaking.

Jim (Nic)'s comment on a heat source is a good one and like him I use a radiator. I have an ali sheet on top of an oil filled radiator that I stand all bonded parts on to cure overnight. I fettle it the following day as it is easier to file/sand than if left longer though it is always possible to work it at any time. I would wait further though before machining the parts if any stress from such would affect the bonded area. It machines well Derek but I have only machined it within using it as suggested. That is, I have not made anything from it as a solid block and then machined it.

I have used other products Martin (OR) Though I have not tried the titanium one I have used the Devcon 'epoxy steel' and also Loctite 'Metal Set' both as good but far more expensive – the extra expense not giving any real benefits over JB in this type of application. Very interesting to hear about the repair to a bore though – I'll bet it has got many engineers out of similar situations.

Like so many in the past I used silver solder to create parts and in some instances such as valve bodies etc I still do but the big advantage that JB has – if it is judged suitable for the task in hand – is that no heat source is required and subsequently no risk of distortion and not to mention the need to clean up flux residue.

The big advantage I found on the Corlis build in using it for the pipework and fittings was that, unlike silver soldering, all flanges could be dealt with in situ and as erected – no need to remove for soldering, making jigs and hoping that nothing moves – so no misalignment issues.

As said pleased to think you are finding this of interest – IMHO it really is a good product and one whose properties are well worth exploring.

Regards – Ramon (Tug)

[Henry BrownParticipant @henrybrown95529]

Been using it for some years for all sorts of applications Tug but hadn't thought about testing it like you have, well done, an interesting read. need to have a look at the Devcon adhesive now, I think it was used occasionally where I last worked for casting repairs but I'd forgotten all about it, thanks Martin.

[Phil H1Participant @philh196021]

Thanks for the clarification chaps regarding the pack type.

It obviously works and looks good. I am very impressed with the marine engine cylinder 'casting' in one of the other threads by Tug and I have noticed Jason using the stuff more than once on his stationary engines.

It just feels a bit like cheating. This JB stuff – like laser cut parts and accurate digital read outs on milling machines is making life too easy. I have always thought that model engineering was supposed to be a long painful experience.

[JasonBModerator @jasonb]

I look at these type of fabrications as one off pattern making as the methods used to build up the "castings" are very close to how the pattern maker would have made up the patterns from various easily machined individual wooden parts then added fillets to internal corners.

So is fabricating in metal less of a cheat than simply buying a casting where someone else has done the hard part of making the pattern?

The big advantage is those of us who choose to fabricate and cut from solid have an unlimited choice of subject and scale as we can make what we want rather than being limited to existing designs and then only ones where castings are still available. The JBWeld allows us to use materials (cast iron) that is not the easiest to join by the usual methods that can be used will steel, brass, bronze etc.

[Ramon WilsonParticipant @ramonwilson3]

Posted by Phil H1 on 16/03/2021 20:02:09:

It just feels a bit like cheating. This JB stuff – like laser cut parts and accurate digital read outs on milling machines is making life too easy. I have always thought that model engineering was supposed to be a long painful experience.

Hi Phil,

I have to say I've never considered using digi readouts on a mill as cheating but more a means of producing accurate work without the worry of backlash and counting turns . I've never bothered on the lathe but boy would I miss their facility on the mills if they packed up.

As for JB W – well this is one of those occasions where it very much depends on ones outlook. Lets face it castings are expensive at the best of times not to mention the possibility of misalignment, blowholes and hard spots. I know suppliers will (should) replace them if so but the frustration of machining something only to find well in the process that its of poor quality is not something I'd be happy about. The potential wait for a replacement before you caan start all over again is another matter too.

Castings, after all, are the means to replicate a part over and over but for the most part 'we' only need the one. Making it from barstock, not neccessarily from cast iron, to replicate something similar is to my mind a much easier road to take. One of the nicest aspects is that for the most part one has very clear datums from which to start.

So yes, it does take it away from the concept that 'model engineering was supposed to be a long and painfall experience' and though I'm sure that came from someone with his tongue firmly in cheek it's never been one I've subscribed to

We are all different but personally, from my perspective a part has to be fit for purpose and as long as it is then the means of manufacture has to be a better road if the surface can been smoothed out and the journey eased along the way – that does not mean taking shortcuts though

Regards – Tug

[not done it yetParticipant @notdoneityet]

Not a high temperature and no pressure, but I saw a cracked water jacket on an engine V’d out and filled with JB weld rather than going the risky/expensive route of cast iron welding or stitching. I believe that engine is still watertight after well over ten years.

[Nigel Graham 2Participant @nigelgraham2]

That's all in all a very encouraging thread for me.

I have had works experience of filled epoxy-resin products, one paste as-bought, another a 2-part 'Araldite' a lot less viscous than the familiar version in a tube; but to which we added slate powder as a filler.

However this material looks as if it will help me out of a hole, or more accurately, steam-passage, I created for myself a long time ago when what seemed an good way to produce the passages in a compound engine block carved from a solid block of cast iron, has now given me a headache with its end-plates and the valve-chest studs.

It would seem I could re-machine the block to fit an insert sealed in with JB Weld, to divert – and significantly shorten – the passages to where they should be.

+

Curious definition of model engineering… that it should be 'long and painful' . Who the heck originated that? We can't deny our models can take a wee while or six to build, but "painful" ?

The essence of model-engineering is creating engineering projects as a leisure pursuit – be they scale replicas of 100 year old machinery made to long-established plans, or up-to-the minute CAD/CAM developments of our own designs.

The essence of engineering is – or should be – making the desired item with the most appropriate materials and in the most appropriate and efficient way, where efficiency is not necessarily financial by any means; and where solving the problems may be a considerable technical, hence intellectual, challenge.

Whilst the essence of a leisure pursuit is that it should be enjoyable, without losing sight of the intellectual challenges. Remove the drudgery of hours of manual sawing and filing by all means, but the mechanised replacement techniques still need a lot of skill – just different and arguably deeper skills. Take great care to replicate the fine details on a Gresley or Stanier locomotive – certainly – even if its cab is rather un-prototypical brass; but that doesn't mean you can't use modern sheet-metal fabrication methods to a CAD-produced design for your club's passenger-trucks.

In other words, think "Engineering" first, and "Model" second – the latter describing the projects not the discipline.

And enjoy it!

[Bill PudneyParticipant @billpudney37759]

Probably ten or eleven years ago I had to make a new piston for a 2.5cc compression ignition engine. At the time the simplest solution was to make the cast iron piston like a tin with one end removed, make a carrier for the gudgeon pin and glue the whole thing together. The I did a bit of research on high temperature epoxies, as the underneath of a piston in a high revving (15,000 rpm plus) engine would be likely to get fairly hot. JB Weld seemed like it was the best candidate. So very carefully everything was cleaned, and cleaned again, the conrod was assembled into the al.alloy carrier with the gudgeon pin. The JB Weld was VERY carefully applied, the conrod, pin, carrier was assembled, and left in a warm place for a day to cure. The motor was carefully assembled and the new piston run in. Ten or eleven years later this motor after a lot of use is one of my favourites, it starts from cold in one or two flicks, and revs to well over 15,000rpm…..Thanks to JB Weld!!

cheers

Bill

[not done it yetParticipant @notdoneityet]

Bill,

Was that flat components glued together, or did you arrange for the JB Weld to ‘key’ by roughing or drilling (on the tosh?) for extra grip?

[Ramon WilsonParticipant @ramonwilson3]

Hello Bill,

That is interesting to hear, especially it's longevity. I've often thought about making a composite piston but always been reluctant in case it separates under running conditions. It would certainly make captive wrist pins an easy option but of course would not be able to be dis-assembled once bonded.

You say the pin carrier was al alloy but assume the piston was cast or steel? – it would certainly make the internal machining so much easier.

I have no plans for another engine at the moment but if I do I'll give this method a try

Regards – Tug

[Bill PudneyParticipant @billpudney37759]

hello Tug and NDIY

The part of the piston that is in contact with the cylinder is from cast Iron. The shape is like a bean can with one end open. The closed end is the crown of the piston, and is about (from memory) 1.2mm thick, the cylindrical part is about 0.8mm wall thickness.

What I described as the carrier is a bit of 2024 T3 al. alloy, made so that it is a smooth and snug fit up inside the piston, to a positive stop when fully home. This seemed to be important to keep the gudgeon pin at about the right height. Bearing in mind that the bore is under 15mm, it will be appreciated that the carrier is fairly small. From memory it was drilled through about 6mm dia, the gudgeon pin was cut from a 4mm diameter needle roller and carefully reduced in length until it would fit in the piston. No especial grooves or other keying devices were used, I just didn't try for a super smooth finish on the inside of the piston, and outside of the carrier.

I claim no originality as this method was used on the first ETA 15 back in the early 60s, if not others. In fact it was reassembling my ETA 15 that gave me the idea, for my motor. Yes Tug, if there are any problems, there is no way other than destructive diassembly, but the advantages of a captive, floating gudgeon pin outweigh that (minor) problem in my opinion. Interestingly the weight of the composite piston, gudgeon pin and conrod is marginally less than the weight of the original piston/pin/conrod, from memory about 0.5 of a gram.  So not enough to get really excited about, but worthwhile.

The motor has been flown a fair bit, initially in a CL Peacemaker, which it dragged around quite impressively on 60' lines. I too wondered about it all falling apart, but thinking about it I realised that the JB Weld was always in compression, I stopped worrying about it then!!

cheers

Bill

Edited By Bill Pudney on 17/03/2021 09:34:38

Edited By Bill Pudney on 17/03/2021 09:37:33

[Ramon WilsonParticipant @ramonwilson3]

Thanks for that input Bill.

My thoughts had been for the piston crown and pin carrier as one piece with the skirt as a separate part. It was the thought of the potential for the skirt parting company that put me off trying

I can see the logic of your method is a far better option and as you say the JB is always in compression. I will certainly give it a go if I make another engine – indeed it might be a good enough reason to make another engine.

It's your last paragraph that gives the real reassurance though – if it stands up to powering a Peacemaker then it will withstand most that it's expected of it I'm sure. BTW was this your Sugden Special?

I have the major parts of a JB Atom save piston and conrod. A lovely little 1.5 that is worthsaving. The original had a ball ended little end – I'm thinking this may be a viable way of getting round that issue.

Cheers Bill, thanks indeed

Tug

 

 

Edited By Ramon Wilson on 17/03/2021 11:05:54

Edited By Ramon Wilson on 17/03/2021 11:06:53

[Phil H1Participant @philh196021]

Tug,

Yes, tongue firmly in cheek. And yes Jason, you are right. I prefer to see fabricated or machined from solid rather than the use of castings.

Nigel, painful? My association with Rob Roy that I started in 1977 and is still at the chassis stage does kind of feel a bit long and torturous but I still seem to keep going for some weird reason.

[Ramon WilsonParticipant @ramonwilson3]

Keep at it Phil, it took me 40 plus years to build my Wide a Wake steam launch from the initial intention and tentative start in 1972 – enthusiasm can come from unexpected quarters at any time so don't despair quite yet – you never know, you know

Regards – Tug

[Bill PudneyParticipant @billpudney37759]

Hi Tug, Thanks for the kind comments!! The motor with the composite piston is a PAW 15 TBR CT….that's 2.5cc, Twin Ball Race, Combat Tuned. It's one of two motors that I bought in about 2005 when I intended to use them in Vintage Combat. It turned out that I was too old and slow for Vintage Combat, but finding that out took several attempts and the motor in question was buried in the sand that is our flying field. As a result of which the piston was damaged, requiring replacement.

I still haven't built a model for the Sugden, but it's likely to be a Mercury New Junior Monitor.

cheers

Bill

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