R2716 75070 poor runner

[Farang]

Just bought this item at an exhibition but it is a poor runner. When power is applied it will move slowly but then at a particular point in the wheel's revolution it locks. Give it plenty of power and it will run steadily.

I'm wondering if it's the gears? Any advice gratefully received! This is a weathered loco, when was it produced?
As an aside it would be helpful if Hornby showed the year of manufacture on the box label.

 

[adb968008]

There could always be a unique fault on this loco, but Mazak rot  has been reported on the three original 4MT models of 75070/1/2.

 

You may consider removing the speedo from the wheel, then the body from the chassis, check see if everything is tight, or if any corrosion exists.. the motor retainer / gear cover was known to corrode, this could cause locking or movement issues, and both motor/ top most gear could become unseated.

 

If this is the issue its Service sheet 337, item 1 Hornby X9978 thats the spare you need, both parts.

https://support.Hornby.com/hc/en-gb/article_attachments/360016257840/HSS-337C-Class-75000_2_.pdf

if not and its all tight, then maybe post some pictures whilst the body is off to allow others to have a look and suggest the issue.

 

 

 

 

 

 

Edited September 22, 2021 by adb968008

[atom3624]

Is there any slop and interference in the valvegear linkages?

 

Al.

[Fireline]

If it locks at one point on the rotation at slow speed, you have a cracked gear. I would suspect the gear immediately below the worm. While you are there, check the mazak in the motor mount that covers the worm.

[Markeg]

Fireline is correct.  I have R2714 75005 and I had the same issue and checked the gear below the worm.  It is cracked. I contacted Hornby, but no reply after several months.  I tried Petersspares, but they are out of stock as are New railway modellers website/shop. I ordered a few spare gears from NRM shop to see if they would do the job, but they wont.

 

So just have to wait for some to come through from Hornby.  X9993 is the code you will need. around GBP10.31.

Hope this helps

Mark

[MikeParkin65]

Just a note of optimism - if the loco has been stored it may well be that the grease has gone hard. Means a strip down, clean out and relube but you'll be 3 quarters of the way there if you are going to check for a split gear anyway. Had the same issue with both an A3 and a Britannia that had been stored for 8 to 10 years each. Both perfect runners now

[Farang]

Thank you all for your comments.

I did remove the body and inspect the mechanism. There is no sign of Mazak rot and the gears were lubricated. So I suppose it must be the gears. As no one has these in stock I'm not going to wait for what might be a considerable time so I shall return it to the dealer when I see him in November. Pity as it's a nice model. I had to return a T9 which suffered Mazak rot. That too was a

nice model except for the bogie tender which did not have bogies! But that's another story.

[The Johnster]

TTBOMK T9 tenders were 8-wheeler in a rigid frame, a bit like an inside bearing version of LNER pacific tenders.  Later Urie locos for the LSWR had bogie tenders as did some Lord Nelsons.

 

As well as the above advice, take the motor out of your loco and push it gently by hand, checking for tight spots as you go and looking for fouling in the motion, such as a coupling rod or the front wheel crankpin rubbing on the rear of the connecting rod.  This can usually be sorted with a little gentle persuasion.  Or the loco may have been overlubricated, a very common problem with 2h locos whose previous owners have reacted to stiffness by putting more lube in, which may temporarily solve the problem but the excess lube picks up crud with jams up the works again.  Solution to this is to remove the existing lubricant (I use a rattlecan switch cleaner spray followed up with an old toothbrush) and relubricate with a lubricant of your choice (I use a non-mineral machine grade oil recommended by my local Antics as safe with plastics, applied with a hypodermic syringe, but a drop on the end of a pin will work).  The trick is to use as little lubricant as is needed for the job with no surplus to attract crud. 

 

Split or cracked gears usually, but not always (that would be too easy!), manifest themselves with a rotational click, louder in one direction than the other.

[Farang]

Sorry, what is the meaning of TTBOMK?  The LSWR T9 8-wheel tenders were on bogies with inside bearings. Urie bogie tenders had outside bearings. So why did Hornby produce a tender without bogies? I'd guess because with bogies it wouldn't traverse second radius curves. Keep in mind that Hornby is making toy trains.

[spamcan61]

to the best of my knowledge. I had to think for a mo!

[Wicor-Models]

20 hours ago, Farang said:

Sorry, what is the meaning of TTBOMK?  The LSWR T9 8-wheel tenders were on bogies with inside bearings. Urie bogie tenders had outside bearings. So why did Hornby produce a tender without bogies? I'd guess because with bogies it wouldn't traverse second radius curves. Keep in mind that Hornby is making toy trains.

 

On 24/09/2021 at 10:25, Farang said:

Thank you all for your comments.

I did remove the body and inspect the mechanism. There is no sign of Mazak rot and the gears were lubricated. So I suppose it must be the gears. As no one has these in stock I'm not going to wait for what might be a considerable time so I shall return it to the dealer when I see him in November. Pity as it's a nice model. I had to return a T9 which suffered Mazak rot. That too was a

nice model except for the bogie tender which did not have bogies! But that's another story.

To the best of my knowledge T9s never had bogie tenders, just 6 and 8 wheelers.  https://sremg.org.uk/steam/t9class.shtml

That should indicate which loco had what tender and when they had it, T9s and tenders are a tricky subject.

[Farang]

The 8-wheel tenders attached to the T9s and other Drummond locos were BOGIE tenders. You may add to your knowledge by looking at Don Bradley's book: LSWR Locomotives The Drummond Classes (Wild Swan 1986).

[Theakerr]

For Gears check shapeways.  there are a number of 3D printed gears there

[Wicor-Models]

13 hours ago, Farang said:

The 8-wheel tenders attached to the T9s and other Drummond locos were BOGIE tenders. You may add to your knowledge by looking at Don Bradley's book: LSWR Locomotives The Drummond Classes (Wild Swan 1986).

You are quite right I don't know what I was thinking at the time, the T9s were all but 15 built with 6 wheel tenders but the last 15 did have 4000 gallon bogie tenders.

[MikeParkin65]

2 hours ago, Wicor-Models said:

You are quite right I don't know what I was thinking at the time, the T9s were all but 15 built with 6 wheel tenders but the last 15 did have 4000 gallon bogie tenders.

Thanks @farang  - I've learnt something new (which is what this forum is all about :))

Edited September 28, 2021 by MikeParkin65

[The Johnster]

Me too!

[Markeg]

Going back to the split gears issue.  I have fixed mine.

I had a thought after CBrooks122000 on 24th september commented he was suprised none of the gears fitted the 4MT.

I thought that two of them were the same, but the axle/pin was too wide.  So I used the electric bench grinder to narrow the axle/pin and now it is working.

 

Mark

[Mallard60022]

 

Mine has Mazak Rot in the Motor mounts.

P

Edited October 6, 2023 by Mallard60022