More on the Mamod Brunel locomotive!

A very popular starting point for Live Steam. With their low cost comes a number of problems which can be discussed here
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Chris Cairns
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Post by Chris Cairns » Sat May 10, 2014 12:34 am

Sorry Mike, I was not quite specific enough with my descriptions.

Version 3 has the fixing plates on the outside of the chassis frames but they are clearly screwed on top of the now disused horseshoe cut-outs for the 'O' ring retention (as per your photos here - http://gardenrails.myfreeforum.org/ftopic6329-0.php ).

So as you have the different axle & wheel arrangement I was counting that as a Version 3.

If you get a chance during your upgrade I'd appreciate a close-up photo of those bearings and the fixing plate. I'll take & post one of the 'O' ring retention method for comparison. They look to me to be the same size & shape bearing.

Interesting to hear the driving axle has been raised as that will lower the height of the centre buffer coupling.

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mikewakefielduk@btinterne
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Post by mikewakefielduk@btinterne » Sat May 10, 2014 7:00 am

Chris
Interesting to hear the driving axle has been raised as that will lower the height of the centre buffer coupling.
About 4mm I would guess. Will be able to measure it more accurately when I bring a vernier gauge in from the garage.

I'll certainly get some close up photos for you.


Mike

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Post by mikewakefielduk@btinterne » Sat May 10, 2014 5:17 pm

OK, I've just about completed the re-gearing work, except for the proper axle end plates. Rather than wait a few days for Mamod to send me the correct ones I fashioned four myself. I haven't got them quite the right size as the cogs on the layshaft and drive axle are meshing slightly too deeply so there's a bit of resistance in a couple of places when you turn the axle. Still, I've had the loco running, so overall its looking OK and can only get better when the correct plates arrive.

The overall gear ratio  seems to be around 4.5 : 1

So was it an easy task? The answer is no. I'm quite happy to put together a set of instructions if any one else wants to do the same. Unfortunately I've had camera trouble to can't provide pictures as well.

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Post by kandnwlr » Sat May 10, 2014 9:57 pm

I have maybe missed this, but what´s the gearing on the latest Brunel?

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Post by mikewakefielduk@btinterne » Sat May 10, 2014 11:38 pm

About 4.5 : 1

The original was around 2:1 (I'd need to count the teeth on each cog to be more exact)

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Post by kandnwlr » Sun May 11, 2014 8:44 am

mikewakefielduk@btinterne:100506 wrote:About 4.5 : 1

The original was around 2:1 (I'd need to count the teeth on each cog to be more exact)
That sounds less speedy. Thanks for the info.

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Chris Cairns
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Post by Chris Cairns » Sun May 11, 2014 10:15 pm

Just been discussing upgrading the Brunel with Mike Wakefield and it is felt that the original style drive axle (fitted to the Version 1 & 2 types) may not be compatible with the new gearing.

Image

Image

I would need to be discuss this further with Peter Johnson, Mamod's design engineer, but currently too busy with other projects including the pending arrival of my Thomas Telford.

Chris Cairns

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Post by mikewakefielduk@btinterne » Wed May 14, 2014 8:51 pm

The "Mk11" version has the same axles as version 3 but the fixing plates are shorter as the driving axles have been raised by around 2mm or so as the cog on the axle is a slightly smaller diameter than the Mk1
I'm correcting myself. Its not the driving axles that have have been raised but the screw holes for the fixing plates that have been lowered because the layshaft is also lower. The locos ground clearance is the same as before.

Have just about completed re-gearing of the Brunel and have test run it on both the rolling road and the part of the garden track that isn't under construction. Seems OK but not yet as free running as before.Of course some parts, including the layshaft bearings are completely new, so there will be a degree of running in to be done.

Have discovered one of the driving wheels has been drilled off centre so the wheel moves slightly up and down as it turns. I only noticed it today because the new Peco track is far more level than the old Mamod track I'm replacing. Its a bit embarrassing as I've owned my Brunel since 2012.

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Post by Bill/Rubery » Mon May 19, 2014 10:16 pm

If Mamod have a new lower geared Brunel now in production I wonder if Mamod will sell me a later chassis and I can transfer all the 'good' bits over to the newer Brunel??
Regards, Bill/Rubery

www.amalgamatedconserves.org.uk

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Post by mikewakefielduk@btinterne » Tue May 20, 2014 9:09 am

I'm sure they will sell you the necessary items, but it will be expensive as the loco with the new gearing has had other alterations as well. In particular the cylinder is lower. The boiler has also been redesigned with  the pressure gauge now at the rear, the chimney flair at the top removed,  the regulator location reversed and the drain for the steam oil lubricator moved, although these latter changes aren't necessary for the re-gearing.

You'll need:
 * new left and right side frames
 * new rear plate with different cut out.
 * new boiler support plate with different cut out.
 * new con rod
 * new slip eccentric rod
 * 4 new plates to retain the axle bearings
 * 4 new cog wheels for the new gearing.
and, if your existing axles are retained by stretched O rings, you'll also need:
 * a new driving axle
 * two new driving wheels.

In other words, the only things you'll retain from your existing Brunel are the boiler, the burner plus gas tank, the cylinder assembly and the cosmetic bits plus buffers at either end of the loco.

The most expensive items are the 4 new cog wheels. Naturally I've no idea what they cost Mamod but I do know how much it costs me, as a clock restorer, to purchase replacement wheels. As you'll see if you search the internet for "spur gear wheel cutting", it will cost you upwards of £25 per wheel.

I've therefore concluded that, unless there's a good reason to want to keep the existing loco, it would be cheaper to sell your old Brunel and then purchase a new one from Mamod.

Mike

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Post by Bill/Rubery » Wed May 21, 2014 12:42 am

Thanks Mike for that valuable information however as I am doing 7/8" scale I have started the conversion up to that scale! My Brunel has new buffer beams and buffers plus the fact that I sawed off the flare on the chimney as the existing chimney was too low for 7/8" scale so I can fit a taller chimney. I wonder if loading the Brunel with heavy wagons would keep the speed down? Pity Mamod don't do a special offer to up grade locomotives that were purchased prior to the current improvements......
Regards, Bill/Rubery

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Post by TTHLRMatt » Wed May 21, 2014 9:19 pm

I need to get around to posting pics of my brunel at some point. I think its the second version but not totally sure!

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Post by mikewakefielduk@btinterne » Thu May 22, 2014 6:01 pm

Well here's the latest incarnation of mine.

Image

I've got 8 days before imageshack start charging me for uploading photos so its a case of use while its free.

The loco has a new name. For quite a while its been "EARWIG" (how can you tell I've got grandchildren? :D ) but in honour of the great man himself has been renamed "ISAMBARD".

Mike

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Post by TTHLRMatt » Thu May 22, 2014 9:40 pm

The only thing stopping mine from running is its regulator being fixed. A new handle needs making but the threads knackered and cant get a spare from mamod as far as I know!
Mine has been nameless mostly but has been called many names, mostly in french or german :lol:

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Chris Cairns
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Post by Chris Cairns » Thu May 22, 2014 10:04 pm

TTHLRMatt wrote:and cant get a spare from mamod as far as I know!
Try contacting Mamod direct. Phone 0121 5006433 (M to Th 07:00 - 15:00, Fri 07:00 - 12:00) and ask to speak to Peter Johnston, their design engineer. Explain your problem and I'm sure Peter will send out the parts if it is an easy fix, and if not will recommend you send it back for repair.

Is your regulator stuck in the fully closed position? I've had that on some of my other Mamod's and then the wheels/knobs just work loose when you try to open it. A pair of needle nose pliers on the regulator shaft frees it off, remove the complete regulator from the housing, Loctite 603 the wheel/knob back onto the shaft, and never leaving the regulator fully closed at the end of a run when the boiler cools down has prevented a recurrence.

Chris Cairns

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