lima crab

[sparkysbox]

Hi there, I've recently bought a lima crab loco,it looks as new,but it just won't run.the motor runs well.can anyone help me with wiring diagram.I'm a bit of a novice.

 Mike

[Simon G]

Hi Mike,

Unless I am much mistaken, the Lima Crab picks up power on one side from the tender and on the other side from the loco.  If you have a meter, you should try to check the continuity between the sets of wheels and the motor.  The most likely problem is the contact between loco and tender.

Best of luck, Simon

[Andy Hayter]

When you say it just won't run, do you mean it does not move down the track (but the motor is running) or when put on the track and power is applied, the motor does not run?

 

These crabs were notorious for the valve gear locking up meaning that either the loco would not run even though the motor was running and the tender wheels going round like made, or they would run with the tender pushing a rigidly locked set of loco wheels.

[ghost-signs.com]

I got one very cheap from ebay as a non runner - mainly because the loco wheels had locked up. This apparently is not uncommon and down to the metal weight distorting the plastic part of the chassis.

 

I managed to pull the sides together using thin wire. A little unsightly from underneath, but invisible when running.

[Totnado]

The problem is all due to the driving wheel connecting rod being split into two which encourages what is known as “Wrong Quartering”, ie., a wheel that carries a lesser load attempts to counter rotate compared to its partner(s) due to sloppy or wrongly set up wheel alignment (quartering – the setting of opposing wheel sets being set 90 to 105 degrees in difference) which emanates from the wheel driving by the real-world steam engine’s timing. Its purposefulness extends to model engineering.

So, the answer is very simple, and contrary to much that is said, all due to the very excellence of lima model engineering. The answer to our problem is to remove the chance of differential wheel rotation and this we do by fixing solid the split connecting rods as supplied by Lima.  The process in our case is to obviate that attempt at counter rotation that causes our engines to stick, stumble and grumble:

1. Strip down the engines motion setting down the tiny extracted machine screws, centre journal  and captive nut somewhere very safe and placing the  connecting rods to one side. Take great care to handle the piston conrod/cross head assembly with silken kid gloves.
2. We are now going to solder together the two differently sized conrod sections which need doing with complete alignment of each section. I found these could be jigged very quickly using electronics Vero board perforated, at 0.1” centres. Vero board is common in most tool boxes or source pre-manufactured pcb., board similarly perforated. It will be found that by running the conrods diagonally across the pcb., holes that the precise and commonly centred holes can be located below each conrod connection hole/journal. These pcb., holes for my purpose, required enlarging to the conrod journal/hole size of 2.2mm and these holes are then occupied by three 2mm bolts or #BA8 (2.2mm) bolts and the end journals are secured by hand tight equivalent nuts leaving off the middle one or leaving quite slack if not vacant.
3. The conrod centre journals which are to be joined together need careful preparation. The external RH., face of the longer rod requires finely filing to remove and clean the polished surface as does the underside of the LH., journal of the  of the shorter rod. Each of these face should be coated in a very thin layer of Fluxite or similar and then carefully tinned using 60/40 solder, I am afraid I do not like using unleaded solder and as this a personal opinion then you may like to use solder of your own and perhaps legal (?) choice.
4. Place and fix the conrods on to their jig following which we patiently heat the two prepared journals which should when 250°C or thereabouts is equally met willingly sweat together and become lifelong buddies.
5. All that remains is to clean up any unwanted solder, wipe away any run/spread flux with a dry clean cloth and reassemble the complete motion making sure that you have quartered the opposing wheel sets to your satisfaction and oiled all moving parts then the action of your locomotive should be that it is running better than it ever had before and better than that Bachmann equivalent (?) I have just saved  you from buying.
6. One more thing that you may like to do is add some weight to that perishingley short of weight locomotive body and the easiest way to do this is by buying some lead shot which when mixed with some good quality PVAc., wood glue can be placed and spread into the underside of the engines boiler and given about 30 minutes has passed this can be assembled on the engine to provide a good intrinsic feel and some dihesive driver wheel grip. If you can’t find any lead shot for sale, then ask as I did, a friend or relative if he or she can split down three one and a half ounce #4 shotgun cartridges to provide 4.5 ounces of additional weight you may add I think up to twice this but for my part 4.5 ounces (127gms) seemed just right, and still left plenty of room.

Happy modelling and I hope your beautiful Lima LMS 13000 Crab runs like a Swiss made clock. Should you have any queries then do not hesitate to ask and I’ll get back just as soon as I can.

 

[DCB]

If soldering the coupling rods cures the lock up problem surely the root cause is excessive slop in the axle holes or wheels loose on the axles.  Is the OO Lima Crab to scale as it looks rather small compared to my cast kit (Wills?) 

[trustytrev]

Hello,

      

 

Is the OO Lima Crab to scale as it looks rather small compared to my cast kit (Wills?)

 

It is HO ie:3.5mm to the foot instead of 4mm.

trustytrev.

[Totnado]

If soldering the coupling rods cures the lock up problem surely the root cause is excessive slop in the axle holes or wheels loose on the axles.  Is the OO Lima Crab to scale as it looks rather small compared to my cast kit (Wills?)

 

I believe it is slop that causes the counter rotation but not that in the axel pockets although this will definitely combine and add to the problem but I definitely found that I could observe the counter rotation when the split conrod attempted to pass the 270degree point of centre driver rotation. The split conrod joint in my case wad not worn as the loco is pristine looking as though brand new with no collection if rail carbon on the tyres. To all intents it seems that this was a serious flaw in the production of the model and as I bought the model 2nd hand it would seem perhaps that the model had never run, "straight out of the box" as they say. Conjecture will arise I am sure but I can assure you that I have conducted the given ploy with excellent, 100 % success.

 

Yours Totnado

[Clive Mortimore]

Hello,

      

 

It is HO ie:3.5mm to the foot instead of 4mm.

trustytrev.

It is a 4mm model just Lima made it too slim. They reduced the width of the loco body to match the tender width. One of the odd features of the Crabs was they were built with L&YR cabs but fitted with the much narrower MR tenders. At the time of the introduction of the Lima model there were may good attempts at making it scale width.

 

As much as I like MR locos for their looks, why did Hughes up and go before seeing his loco being fitted with a L&YR tender to match the cab?

[kevinlms]

It is a 4mm model just Lima made it too slim. They reduced the width of the loco body to match the tender width.

 

As much as I like MR locos for their looks, why did Hughes up and go before seeing his loco being fitted with a L&YR tender to match the cab?

I suspect Lima thought they'd made a mistake & actually tried to fix it.

[bike2steam]

I 'acquired' a Lima Crab about 25 to 30 years ago, and found the distortion in the plastic outer chassis was locking up the centre drivers, I cured the problem by drilling, and tapping 14 BA machine screws each side of the centre axle to the inner chassis block. But disposed of it a few years later after I developed a hate for tender-drives.   

[Totnado]

I 'acquired' a Lima Crab about 25 to 30 years ago, and found the distortion in the plastic outer chassis was locking up the centre drivers, I cured the problem by drilling, and tapping 14 BA machine screws each side of the centre axle to the inner chassis block. But disposed of it a few years later after I developed a hate for tender-drives.   

High Bike2steam,

 

I believe that I might be slightly mistaken in not mentioning the slop apparent on all wheel axels of my engine however I'm afraid I am unable got into my head around the mod that you made, is it possible that you might further expound on your scheme. All given my acceptance that axel slop was apparent in my loco might I add, that without making any alteration to axels or axel pockets the solidifying of the connecting rods proved entirely successful in preventing miss-quartering/counter rotation that had previously evolved into none running qualities.

 

Note to other forum contributions.

 

1]     The notion that this model is of HO scale should be erased as it is known that from sometime in 1977 when I believe Lima stopped 3.5mm/HO production their models were thereon all produced as 4mm/00 gauge. The Crab was not described in Lima's 1978/9 catalogue nor in their price list of 1977 (both on hand) so presumably it was not in production at that time and the earliest date I can find for it to be on sale was 1980. Ipso-Facto: it must be of 4mm scale.

2]     The idea that this model was not constructively well designed juxtaposed against the good engineering principals utilised is most probably the reason why when Hornby purchased the remnants of the dissolved Lima company in 2004 they did not, as they did with all other of Lima's good sound models, use the tooling existing to produce a LMS., Crab.

3]     I can assure anybody contemplating getting a Lima Crab running nicely that the solid conrod principal worked in its entirety for me; no if's and but's but straight out of the box, as is said

 

Interestingly, I am unable to ascertain whether the Bachman Crab uses the two part or single fixed conrod. Somebody must I am sure.

 

Totnado

[bike2steam]

High Bike2steam,

 

I believe that I might be slightly mistaken in not mentioning the slop apparent on all wheel axels of my engine however I'm afraid I am unable got into my head around the mod that you made, is it possible that you might further expound on your scheme.

 

Interestingly, I am unable to ascertain whether the Bachman Crab uses the two part or single fixed conrod. Somebody must I am sure.

 

Totnado

Mmm, a few years ago since the job was done, but now I think I used 12BA screws. But the chassis was stripped down, and the outer plastic section was reaffixed to the inner block by using 3 x M3 machine screws thro' the axle holes. Then 2x 1.05mm holes drilled at 4mm ( it could have been 5 ??) either side of the centre axle centre-line, on both sides of the chassis. Open the holes out to 1.4mm on the plastic outer chassis, and tap the holes 12BA in the metal inner chassis. I used countersunk screws, putting a shallow countersink in the holes in the plastic outer-chassis. Reassemble the complete chassis, and the problem, I had, was cured.

 

Con-rod - or do you mean coupling-rod ? Con ( or connecting rod) rod I think of is the 'rod' from crosshead to big-end, coupling rod is from wheel crank-pin to crank-pin. The Bachmann Crab's, like all well built loco coupling rods, are 2-section, solid coupling-rods mean less flexibility.

In all honesty I would never advise anyone to buy a Lima Crab, the Bachmann version is far superior - I, for my sins, have 5 that work most of the medium sized ( 20 - 30ish wagons) partially-fitted freights on my layout.

[DCB]

I don't think George Hughes thought anyone would be stupid enough not to use his L and Y tender behind the Crab but he had not bargained on Anderson who even wanted to put a standard Midland boiler on the Crab.   ES Cox mentions the Crab in his Locomotive Panorama, how the cylinders had to be raised to clear some ( imaginary ) MR platforms.  The resulting bodgery can be seen on 13000 at York museum, No way was it designed like that, It's obvious they decided to to lift the cylinder centre line after the frames were cut.  Fortunately they only ruined the looks and fitted a stupid tender.  When tested in the 1950s the Crab was better thermodynamically than the Black 5, but would not steam at high outputs, proving Hughes faith in low boiler pressure allied to a big superheater.  It is a great shame Hughes retired when he did allowing the  Fowler / Anderson museum pieces to proliferate, and not even the good ones. How could they come up with the 7F?  Nothing like as good as the LNWR 0-8-0s  and the Garratts.  so much worse than the LNER.  Its a good job they left the Scots to North British, even if they didn't reach their potential until they adopted SR Nelson type piston valve rings 

[bike2steam]

As Billington ( then boss at Horwich drawing office) had instructed E.S. Cox to prepare the preliminary drawings for the Crab using Caledonian plans for a proposed 2-6-0, he should have known about the class from the start. The cylinders were so placed to get them within the LMS composite loading gauge, and were designed as such. But with the rest I agree, yes, Fowler was adamant that the class should include the Compound boiler, but thankfully work had progressed far enough to not warrant the change, to a less efficient boiler.