KRModels announce a GT3 Model

[Pre Grouping fan]

Just had this back from Keith:  

He said despite reservations of the factory and himself with reduced traction. But, he's going with the consensus and carrying it forward like this.

 

Confirmed again it will be a cast chassis/gearbox.

[Stanley Melrose]

On 18/06/2019 at 18:03, Stanley Melrose said:

It looks as if it may be possible to remove some of the intermediate gears to leave only the drive to the centre driving wheels . . .

 

Stan

Seems as if Keith is a realist . . .

Stan

[gary_lner]

1 hour ago, Pre Grouping fan said:

Just had this back from Keith:  

He said despite reservations of the factory and himself with reduced traction. But, he's going with the consensus and carrying it forward like this.

 

Confirmed again it will be a cast chassis/gearbox.

That was a quick turn around. Did Keith mention if the space where the extra gears were going to go is going to be filled in now for added weight? Anything mentioned about the nem pocket and speaker location? 

 

Regards Gary 

 

[Pre Grouping fan]

No mention of the extra space from the now vacant gears but I'm sure that will turn into added weight.

 

NEM pockets will be added now that the external shape is complete.

 

Speaker will live in the void forward of the motor above the bogie. Decoder will live in the tender.

[chris p bacon]

2 hours ago, Pre Grouping fan said:

Just had this back from Keith:  

He said despite reservations of the factory and himself with reduced traction. But, he's going with the consensus and carrying it forward like this.

 

Confirmed again it will be a cast chassis/gearbox.

 

Hmmmm, I fear that just taking out some of the gear train to the leading and trailing wheel set but leaving the worm and 5 gears isn't really a good idea as It all depends on what the gears and worm are made of, and what the tolerances are.   If they were metal and machined to close tolerance I don't think there would be too much of a problem, but if these are nylon or similar there is likelihood of a lot of slack and it would be better if left as the original design.  Just filling the redundant space with metal to make up for the lack of adhesion could increase the wear rate if they are nylon.  There is plenty of space within the body to accomodate a central tower over the middle driver and reduce the gears to 2 or 3 and rely on the rods, if they are a good fit it should have plenty of power, if they are 'slack' it won't.

Whats odd is if KR models think this design will have an issue with adhesion and it's against the advice of the factory why go with it ? The decision should surely be an engineering one as we don't know the materials used.

[chris p bacon]

1 hour ago, Pre Grouping fan said:

No mention of the extra space from the now vacant gears but I'm sure that will turn into added weight.

 

Please don't take this the wrong way, but you are not KR Models. I realise you are in touch with them but you can't really answer on their behalf unless they have actually replied with a definitive  answer.  I say this to avoid confusion over the spec.

[truffy]

15 minutes ago, chris p bacon said:

The decision should surely be an engineering one as we don't know the materials used.

Well pointed out, the danger of the armchair modeller!

 

There are two issues at odds here: the 'better' way of doing things, using the right materials and engineering practices; and the factory's own materials and engineering standards (an unknown).

 

It's at times like this that I'm glad I'm a numpty and have nothing tangible to contribute.

[Pre Grouping fan]

29 minutes ago, chris p bacon said:

 

Please don't take this the wrong way, but you are not KR Models. I realise you are in touch with them but you can't really answer on their behalf unless they have actually replied with a definitive  answer.  I say this to avoid confusion over the spec.

Not at all, I understand where your coming from. I think its going to be a waiting game for either another updates CAD or the actual prototype.

 

The only information on gearing material is "high grade plastic" which was either on here or on one of the facebook posts. That could mean anything. 

 

[cctransuk]

52 minutes ago, chris p bacon said:

 

Hmmmm, I fear that just taking out some of the gear train to the leading and trailing wheel set but leaving the worm and 5 gears isn't really a good idea...

 

I couldn't agree more ! The aim, surely, is to transmit the power from the motor to the driven axle as simply, (and thereby as efficiently), as possible.

 

The easiest way to do this is to mount the motor low, and use the minimum number of gears to connect the motor to the axle, and reduce the high motor revs to a desirable axle rotation. High Level Models have been demonstrating how to do this for some time now, with their comprehensive gearbox range.

 

Why do we need high-mounted motors? Why do we need prop shafts and universal joints? Why do we need multi-gear transmissions? The principles of a simple, compact reduction gearbox can be easily incorporated into a cast mazak chassis block - model manufacturers have been doing it for some years now.

 

It strikes me that the contracting company in China are, for some inexplicable reason, wedded to a design concept that is way over-engineered. Each spinning spur gear absorbs energy, introduces slop and degrades smooth running.

 

What is needed here is the KISS factor - Keep It Simple, Stupid!

 

Regards,

John Isherwood.

[truffy]

Or, the more links in the chain, the more likely the chain is to fail.

[Miss Prism]

14 minutes ago, cctransuk said:

Why do we need multi-gear transmissions?

 

We don't need them, or like them. The manufacturer likes them because they are incredibly cheap off-the-shelf non-precision stock gears. The manufacturer's and/or commissioner's profit margins are thereby maximised. The cheapness is reinforced by the poor balance and the non-existent suspension, neither of which seem to have been considered.

 

It's worth about £50.

 

 

[Colin_McLeod]

The arrangement with the universal joints and all those gears looks like it may have been derived from a centrally powered Co-Co with one bogie removed.   

[Ryde-on-time]

7 hours ago, Colin_McLeod said:

The arrangement with the universal joints and all those gears looks like it may have been derived from a centrally powered Co-Co with one bogie removed.   

That is the philosophy behind the drive train on the £450 Rapido Hudson which seems to work very well. Details can be found if you scroll down their  newletter 92 here:

 

https://myemail.constantcontact.com/Rapido-News-Vol--92---New-Videos--deadlines-and-factory-updates-.html?soid=1101318906379&aid=lAXRjGa-Dq0

 

It does concern me just taking a few gears out if the factory would normally design a chassis with all axles gear driven as I would expect there to be a knock on effect on the connecting rods, something the factory might not be familiar with.  From the start people were asking for a spec of the model loco and it seems apparent there wasn't one, rather than being the best possible model of the GT3 it seems to be what’s easiest and most convenient for the factory

Edited June 20, 2019 by Ryde-on-time

[RedgateModels]

7 hours ago, Colin_McLeod said:

The arrangement with the universal joints and all those gears looks like it may have been derived from a centrally powered Co-Co with one bogie removed.   

 

That thought struck me too. It might be in Keith's best interests to stick with what the engineers know best? An early chassis EP would be advisable to prove the design before concentrating on the pretty bits ....

[truffy]

22 minutes ago, RedgateModels said:

 

That thought struck me too. It might be in Keith's best interests to stick with what the engineers know best? An early chassis EP would be advisable to prove the design before concentrating on the pretty bits ....

But if it is a CoCo bogie design then, as noted earlier, it may not be designed to tolerate connecting rods.

Edited June 20, 2019 by truffy

[chris p bacon]

1 hour ago, Ryde-on-time said:

That is the philosophy behind the drive train on the £450 Rapido Hudson which seems to work very well. Details can be found if you scroll down their  newletter 92 here:

 

https://myemail.constantcontact.com/Rapido-News-Vol--92---New-Videos--deadlines-and-factory-updates-.html?soid=1101318906379&aid=lAXRjGa-Dq0

 

It does concern me just taking a few gears out if the factory would normally design a chassis with all axles gear driven as I would expect there to be a knock on effect on the connecting rods, something the factory might not be familiar with.  From the start people were asking for a spec of the model loco and it seems apparent there wasn't one, rather than being the best possible model of the GT3 it seems to be what’s easiest and most convenient for the factory

 

That's an interesting drive, but I can see a huge difference.

 

The rapido drive actually drives the front and rear axle from identical gear trains with the middle axle coming from the first spur gear.  The location of the motor is dictated by the boiler but that is a large flywheel adjacent to the bearing tower with little free air between the motor and worm. In comparison to the above the GT3's planned drive has 9 gears from worm to front axle.

The issue I can see is that on the Rapido drive as power is applied the first and last axles will start to turn in sync as the drive is balanced, but on the planned GT3 drive the rear & middle axles will start to turn before the front. On a Co-Co or power bogie this isn't a big deal but on the GT3 the rods also link the drive so as the gears wear it will start to be a a bit 'lumpy' as the rods and gears fight each other.

[ThePipersSon]

Have I missed it, or is there still no footsteps up the tender.

[Hilux5972]

10 hours ago, ThePipersSon said:

Have I missed it, or is there still no footsteps up the tender.

You must have missed it 

[adb968008]

23 hours ago, Colin_McLeod said:

The arrangement with the universal joints and all those gears looks like it may have been derived from a centrally powered Co-Co with one bogie removed.   

I must be having one of my invisible post days...

 

 

On 18/06/2019 at 19:57, adb968008 said:

I notice the green colour outline around the drive chain, I wonder if it is plastic ? (The motor housing is also green and often these are plastic).

 

if it were, in that sense maybe this design could be based on a “co” 6 wheel diesel bogie, upsized and slotted in.. for instance the drive chain does look to me, a lot like the Dapol class 52 motor bogie..

 

https://www.dccsupplies.com/item-p-107043/gear-type-1-Dapol-oo-class-52.htm

 

If I was correct it could be a plastic cradle slotting into the metal weight block that holds the motor and thus avoids a split chassis (though the plastic cradle would be two halves).

 

that would pose another question though.. wheels would need a metal axlebox, to not wear out the plastic cradle, where would the pickups be ? - would it be like piko in the tender ?

 

 

...

On 19/06/2019 at 22:29, Miss Prism said:

 

We don't need them, or like them. The manufacturer likes them because they are incredibly cheap off-the-shelf non-precision stock gears. The manufacturer's and/or commissioner's profit margins are thereby maximised. The cheapness is reinforced by the poor balance and the non-existent suspension, neither of which seem to have been considered.

 

It's worth about £50.

 

 

 

The Dapol class 52 bogie costs considerably less....DCC supplies sells a full bogie at £17.. so the China price is probably closer to £5 than £50.

 

rather than price, maybe the factory chose a diesel bogie approach, because their experience is in building diesels or n gauge.

 

I have a pretty good idea which factory this is.

 

Edited June 20, 2019 by adb968008

[woodenhead]

16 minutes ago, adb968008 said:

rather than price, maybe the factory chose a diesel bogie approach, because their experience is in building diesels or n gauge.

 

I have a pretty good idea which factory this is.

 

Do they now have a spare bogie design that may fit a dual current electric loco 

[GWR-fan]

Many years ago I was heavily involved in largescale garden railways and made the "mistake" of suggesting an alternative design to the chosen chassis design  on a very large steam outline locomotive, pointing out the possible flaws in the design which proved to be true as multiple failures were reported.  In an email exchange with the company president I was advised that he would sue me for loss of earnings as apparently no one had returned the product for warranty issues.  I advised him to read of the numerous failures posted on his own company sponsored forum.  It seemed that rather than return for warranty work the owners were rebuilding and repairing their models.  The company president had complete faith in his lead engineer in China and would accept no criticism of the design.  Odd that just a few months later I was requested by the company president to return a largescale switch (set of points) that I had modified and vastly improved for reliable running to the factory so that they could copy my design for production. 

 

To Keith's credit he is listening to social media rather than relying on just the engineering team.  The engineering team will design a drive for proof of concept while we, the purchasers,  want a design that will run reliably and smoothly for a long time,  not simply a few laps of a test track at the factory in China.  In an ideal world a well engineered gear drive will work perfectly as each axle is independently driven so any slop or wear does not impact on the orientation of the axles.  However, strangle the driven wheels with coupling rods as well, no matter how loosely engineered and binding inevitably will occur, resulting in poor running characteristics.  Recent geared/coupled "OO" designs have shown that even new unused models exhibit rough running when production tolerances are not maintained. 

 

As regards the chosen material for the "plastic" gears,  even cheap mass produced designs from the 1960's/1970's for the American market made by Athearn used engineering grade material for their gear designs on their diesel models and I never had an issue with gear wear or gears splitting.  Why to this day knowing that better materials are available,  many manufacturers opt for cheaper plastic gears that tend to split?  I have had to replace many gears on Hornby steam outline models.   

[truffy]

Since the GT3 was a 4-6-0 configuration, is there good reason why the mechanism design shouldn't follow what must be a plethora of kettles out there? Rather than a (possibly overcomplicated) design more befitting a locomotive without connecting rods.

 

Sorry for such a stupid question, and if it made you snort your coffee. But, when crafting your reply, if you could pretend that you're talking to a five year old, that would be quite spiffy.

[Pre Grouping fan]

21 minutes ago, truffy said:

Since the GT3 was a 4-6-0 configuration, is there good reason why the mechanism design shouldn't follow what must be a plethora of kettles out there? Rather than a (possibly overcomplicated) design more befitting a locomotive without connecting rods.

 

Sorry for such a stupid question, and if it made you snort your coffee. But, when crafting your reply, if you could pretend that you're talking to a five year old, that would be quite spiffy.

From what's been said on the facebook page/other comments.

 

The design for the chassis was down to the factory designer/engineer and their experience with traction/power. It breaks what is essentially a standard in the UK for steam chassis.

 

We don't know who the factory is/what they have produced but keith has said he own products made by them. Someone noted they have a good guess at what factory it might be but nothing more.

 

[truffy]

Thanks but that’s not really what I asked. A number of suggestions have been made here, based upon variations of the original theme. And I was just wondering how these compare with the running design of a 4-6-0 model. 

[polybear]

2 hours ago, Pre Grouping fan said:

From what's been said on the facebook page/other comments.

 

The design for the chassis was down to the factory designer/engineer and their experience with traction/power. It breaks what is essentially a standard in the UK for steam chassis.

 

We don't know who the factory is/what they have produced but keith has said he own products made by them. Someone noted they have a good guess at what factory it might be but nothing more.

 

 

Perhaps if the factory already has a similar powertrain in an existing (maybe diesel?) loco then swapping the wheels for a set with crankpins & connecting rods would surely be a quick & easy experiment and should tell them if the system has possibilities?