chassis breakages

i was looking at a friends Hornby T9 as he was complaining about poor running and on removing the body found the chassis

was broken into three pieces this loco was a replacement for an earlier model that had been sent back to hornby because  of

poor running to cut a long story short it took over a year to recieve this replacement. where the front of the chassis had broken

off someone had held it in place with the black putty used to retain the wiring. my friend is now getting in touch and sending

 these pictures . very poor quality that seems to be spreading through Hornby like a virus !

 

The fractures are due to the "MAZAC Pest", which was a chronic issue with many G-F models. Often due to impurities in the mix and impossible to cure. Poor QC, no excuse these days. NFFIP. And very difficult to achieve a good repair as the process is unstoppable. Tough to solder (almost brazing, given that mass), and needs special solder and flux from C+L, but it can be done.

I've used cyanoacrylate and epoxy to repair MAZAC fractures. Neither are 100% permanent, as the MAZAC will continue to deteriorate either side of the repair. The joint has to be scrupulously clean. Small brass keeper plates screwed in place over the fracture help (or pins or screws through the fracture). Drill (and tap for screws), glue (and screw). Use 24 hour Epoxy, much stronger than the 5 minute variety.

Whatever you do will be a temporary repair. Getting the gear cover in place is the most important, a brass extension can be used for the front bogie.

This appears to be a very common fault with the T9. There is an  extensive thread on RMWeb  (http://www.rmweb.co.uk/community/index.php?/topic/98918-hornby-t9-broken-motor-housing-retainer/)

Nigel

 

It might take special or at least acid-flux solder to solder ZAMAC (That's the order I'm used to for the letters) die-cast, but it's probably the most solid fix there is for breakage, ZAMAC-rot or no. Most glues will make a weak bond when just gluing the metal to itself without a plastic "bridge" (and even that isn't wholly reliable, plus it can cause clearance issues), in my experience, and the glues that do work can end up going on thick enough that they cause clearance issues (which is why I'm looking into getting the necessary solder - the breakages I'm dealing with are on Transformers toys)

ZAMAC in the US, MAZAC in the UK. Alloy family of zinc, aluminium, magnesium and copper. Seven different mixes, #3 is commonly used. No idea which mix is used for models, probably #3. Beloved of model locomotive manufacturers as it keeps the weight down compared to a lump of steel.

Soldering ZAMAC/MAZAC calls for aluminum-rich solder, no lead, and corrosive flux. The flux I have experience with generated fluorine and boron gas, fume hood with air extraction and/or respirator recommended. And it needs a big tip and a really hot iron. The generation of an inert gas when soldering (or an inert gas supply, e.g. argon or nitrogen) is essential because of the oxidation of the zinc, aluminum and magnesium is instantaneous and gives a cold solder joint. In my experience soldering fractured ZAMAC/MAZAC castings where the Zinc pest (lead or other heavy metal contamination) is present is a temporary fix that lasts no longer than cyanoacrylate or epoxy glue (6 months to 2 years). Disintegration merrily proceeds either side of the repair, which fractures again. It's a lost cause - there is no cure. I stopped doing it.

This was a problem that plagued model makers in the 1950's. There is absolutely no excuse for this today. Either Hornby are not capable of ensuring QC/QA with their contract manufacturer in China 6000 miles away or they knew about it and sold the models anyway. China has purity standards for ZAMAC/MAZAC ingots, but unlike other countries not for castings. What goes into the factory may not be what comes out. Cross contamination with other alloys that contain lead (various white metals used in bearing manufacture for example) is also a known issue that is easily avoided. Again, this is a QC/QA issue. Bottom line - a chassis with the "pest" is NFFIP.

It's a pity because the T9 is a  nice looking model that deserves better. One possibility is the milled T9 mainframes from Allan  Gibson Workshop (LM1-82, £11.50 including VAT). Might require a bit of fettling, but definitely no rot in the future. Ask Colin at AGW if they easily fit the Hornby T9 or if he knows what's required.

Nigel


   

Buyers Beware!
Chassis problems are not unique to the Hornby T9.
2 fellow club members from my real life society have had problems with the chassis of their Hornby West Countries. On each occasion this problem manifested itself when one of the rear drivers would start to run concentrically. Unfortunately by the time I got to look at them the conrod holes had gone oval and were therefore only good for scrap.
Spares were a nightmare to obtain and when they were obtained from independent retailers it became obvious that there are many detail differences between production runs of the loco. The replacement bits did not fit!
The only real solution was to obtain a West Country chassis from PDK Models.
PDK also make a chassis for a T9. The good news is that their chassis is a fold up for OO gauge as are the West Country Chassis's. Do read the instructions as the main fold is with the etched groove on the outside!
With the Gibson chassis bits you will find that both horn block spaces are milled out. This is to accommodate the Alan Gibson sprung horn block. Some of the bits can be fiddly but courage mon braves; the system works well!
Do not think of fixing the standard chassis as the short cut, it most definitely is not! The reason being that the relationship between the conrods and the crank pins is critical. Get this wrong and the chassis will never run. The thickness of glue or solder could be enough to put everything slightly out.
I am happy to answer questions.

Finally, I had a broken propriety chassis once. I am now a loco kit builder. Do take the plunge; it could be the start of a fascinating journey!

Hi Mark,

You're spot on, repairing MAZAC that is disintegrating is a lost cause. Doing a temporary repair with cyanoacrylate or epoxy while building a new brass or nickel-silver chassis would be my approach.

Zinc demand far outstrips supply, mines are shutting, prices will increase, contaminated zinc will become much more common as it gets recycled as opposed to new. Expect much more of this in the near future. The issue for the consumer is that it doesn't become evident for a few years, by which time the manufacturer has moved on and a spare chassis is non-existent (but would probably suffer from the same problem anyway).

Nigel

Well, we might also expect a shift to the chassis being made of plastic instead of metal.

This bad news about die-cast parts may be a problem for producers of model trains…. but part of me is cackling because of what this will do to the "If it doesn't have any die-cast parts it may as well be a cheap bootleg" snobs in other hobbies.

Having read all that and not understood a word of it !, I wonder for example what metal Marklin and Flieschmann chassis' are made of ?

Allan.

Hi Allan,

ZAMAC. And there are known issues with various models/years. Same for Roco and Lima. Takes about 5 years to become apparent. It seems to come and go, which means a lack of QC/QA on the zinc. The various continental forums are full of this. Usual reponse from the manufacturers - deafening silence.

Brendan's comment re a plastic chassis are interesting. Properly designed it would take the torsional forces of modern motors, but screw/bolt threads would be an issue. Weight (mass) would be another issue. The mass required fills the body. Not sure I would want to go back to rubber tires with DCC. OK for diesel railcars and the like with the motor over the wheels and not pulling anything, but something that pulls half a dozen passenger cars needs decent traction. The Mainline Warship was plastic, pulled OK with the original traction tires, change the wheels for decent metal ones and they struggle with 2-3 cars.  Add weight and the chassis deforms…

Nigel

Thanks for that Nigel, certainly makes things a lot clearer.

As I recall ( or quite possibly not !) that all the old Wren/Triang chassis were made out of the same stuff we are talking about here and you can still find 50 plus years vintage models for sale on Ebay and at auctions where the chassis are as good as the day that they were first built. If not, then why not use the same metal as used then on the models as built now ?

I knew of a chap once who milled a chassis for a triang loco out of a solid block of nylon/Teflon (?) ( mind you, I don't know why he did !) which then suggests a chassis could also be milled out of a solid bar of brass or even steel. Probably both stupid suggestions but then again I only ever work in cardboard !

Cheers.

Allan

Hi Allan,

Golden oldies. Some of those old diecast chassis's are as good as the day they were cast. Some went the way of all things. The "Pest" seems to be associated with the lead, cadmium or tin content of the zinc. Moisture accelerates the process, which attacks from the surface inwards. The "Pest" is eliminated if high purity zinc (99.9%) is used, along with the addition of magnesium. All researched in the 1920's. A moisture barrier will stop it starting or prevent it progressing in lightly affected models. Low lead content requires distillation, not a cheap process. Zinc alloys are recycled, contamination with lead or tin is easily done. All those dead NiCad batteries probably don't help.

If ZAMAC alloy is being used that meets the specifications for composition the "Pest" is not going to occur. If it occurs it's not a ZAMAC alloy casting. And it's probably a good idea to keep collectable models away from wood storage cases and with some silica gel desiccant to mop up the moisture. Any manufacturer that sold a model in the past 20 years that is coming down with the "Pest" should step up and replace or offer a refund. Some do, many are deaf. Caveat emptor. Especially older models.

Nigel

Thanks  Nigel.

My model shop never told me any of this 'pest' stuff when I bought my first Triang loco !

So, what are todays loco chassis made off ?

Cheers.

Allan.

 

 

Re: the issue of a plastic chassis deforming under weight, I think making the bottom plate out of steel solves that. I say that because I once bought a Life-Like 0-4-0T with a plastic chassis whose bottom piece was steel, and the chassis wasn't deformed despite the presence of both a boiler weight and a big fat can motor.

Allan, it's the same stuff, it's just getting bollixed at the mixing vat more often than previously.

Thanks Zelda.

As with anything these days. Since it's been such a great success,  then let's try doing it cheaper and bollix it right up. I call it 'Trading on a name'

Allan

[user=1427]allan downes[/user] wrote:

Thanks  Nigel.

My model shop never told me any of this 'pest' stuff when I bought my first Triang loco !

So, what are todays loco chassis made off ?

Cheers.

Allan.

 

 

Hi Allan,

Hopefully a ZAMAC aloy to the appropriate specifications, but as Brendan so politely put it, we're at the mercy of the contractor in China who is die-casting the chassis's for the "manufacturers" such as Hornby, and who is only concerned with the profit margin. GIGO applies here. Unless there is adequate QC and more importantly QA who knows what goes into the mix. The caster probably doesn't know, the ingots are probably sourced in. It's a good argument for bring manufacturing back and paying 25-50% more for a quality product.

Nigel

[user=1916]ZeldaTheSwordsman[/user] wrote:

Re: the issue of a plastic chassis deforming under weight, I think making the bottom plate out of steel solves that. I say that because I once bought a Life-Like 0-4-0T with a plastic chassis whose bottom piece was steel, and the chassis wasn't deformed despite the presence of both a boiler weight and a big fat can motor.

Allan, it's the same stuff, it's just getting bollixed at the mixing vat more often than previously.

Hi Brendan,

That or a couple of brass I channels attached to the plastic floor to give some rigidity. Although I've used a couple of styrene I channel with some success. Takes a reasonable weight afterwards.

Drifting off topic here.

Nigel

Hi Ian,

I did some checking. Zinc ingots in China come in various grades, up to 1% lead in the cheaper ones. Throw one of these into the ZAMAC alloy mix and the damage is done. As I said, GIGO. If you want to design a casting mold getting 100 chassis done is very cost effective (100 is about the minimum run. What you do with the other 99 is up to you).

Based on some examples of very complex castings I reckon a die-cast chassis run of 1000 for a model locomotive would be around $5-$10 per unit (diesel lump and steam lump). ZAMAC alloy is $1000-1500 a ton, enough for 2000-4000 chassis. The casting machines run between $10,000-$20,000 retail, which would be amortized over maybe 10 years. The major cost is the tooling, which with CAD is not as expensive as the old-fashioned "master tooler" who used a lathe, mill and hand tools. 

Which begs the question - why isn't Hornby doing a small run of 100? They have the mold, although I was reading recently that they have no idea where many of their older molds from 5-10 years ago are in China, which could explain their reluctance to address the issue to the satisfaction of the punters who have parted with hard-earned lucre.

If this was a car the manufacturer would be doing recalls, even with 10 year-old models.

Nigel

Hi Nigel.

Whilst everyone sings the praises over cheaper products from China unbeknowingly we are also singing the praises for substandard products that maybe look good on the surface but in reality what we are getting is skin deep engineering.

As they say, you gets what yer pays for - and obviously not even that sometimes.

Sadly, and in the car industry in particuar, badge engineering sells cars faster than what lies beneath that glossy paintwork - I mean, what on earth are Fords doing building Aston Martons and filling the intereiors full of cheap Mondeo parts and BMW building their version of a Rolls Royce powered by their own V 12 power plant and  mucking  about with BMC's Mini to such an extent that  at 20 grand a shot it just ain't a Mini anymore and certainly nothing like the one I bought new for 600 quid and a couple of years later sold for 60 with a rust ridden subframe, burnt out clutch, knocking big-ends and sagging doors. But at least it was a REAL Mini !

Yet nobody took up the Austin Allegro - wonder why…

Hi Allen,

It's a valid point. Unfortunately unless a lot of noise is made nothing will happen. The model press for the most part is too dependent on advertising to provide independent, unbiased review, sending a letter is a WOT, strident demands for a replacement and or money back coupled with some hovering legal eagles might do something. 

Minis - this is definitely wandering off topic. Give me BMW's version over the old one any day (with the exception of that daft supercharger/water pump design which I think they changed).

Nigel

[user=1632]BCDR[/user] wrote:

Minis - this is definitely wandering off topic. Give me BMW's version over the old one any day (with the exception of that daft supercharger/water pump design which I think they changed).

Nigel

…and, including of course, the outrageous price tag !

Allan