Chassis and motors in 7mm Newbie questions!

[woko]

Hello folks

 

So im guessing I'm possibly going to open up a can of worms here, and ask a bunch of dumb questions so I would like to apologise in advance if you folks get this a lot, but I would greatly appreciate any help you can give me.

So i'm looking for some advice on how to go about building a chassis and adding a motor, wheels and coupling rods for this L77/N7 I have porotype 3d printed. Originally I was thinking of using a Dapol Jinty Chassis, and fabricating a small pony truck at the back! @thegreenhowards Idea which is a sound idea and worked extremely well beforehand when we used the Dapol Terrier chassis for S56/J69.

However I have since printed out the body for the N7 loco, and I have found the motor on the jinty sits far to forward, resulting in having to cut a section out of the boiler up to the first boiler band in order for the motor to fit properly, which in my opinion would spoil the look of the locomotive!

So I am thinking Rob, why don't you just see if you can build/3d print a chassis for this loco instead, it be worth trying out, seeing if i can get it to work!

I know I can source the wheels from Slaters I will need 3 pairs of 4'10 wheels, and a pair of 3'9 wheels for the trailing set at the back, this is as much as I know that I need so far! Not great I know ;)

 

So my questions are:

 

What motor should I go for, a biggie I know, but I haven't a clue about this, and where to start?

Where is the best place to get coupling rods for the N7, I believe Premier Components do a set?

Does anyone know the standard width for a 7mm chassis out of interest for when I start to build this in 3D?

The hole diameter for the axles according to slaters is 4.763mm so making this slightly larger say 5mm would hopefully allow the axles/wheels to run fairly smooth? I could also create some wheel spacers to be set inside the chassis to add further support!

Do I need to add weight to the chassis, and if so how much is recommended and what to use?

Have I forgotten anything or over looked something glaringly obvious?

And is there any previous threads or videos that I can take a gander at that help with a lot of these questions?

 

Many thanks folks in advance an apologies for the Noob question on this but any advice is greatly appreciated here

 

First test/prototype print below, still some cleaning up to do and there are some issues I need to fix, a bit of warping which just needs some supporting columns inside to fix this issue, and some strange chamfering off in the corner that was the result of an unsupported area I believe. All other details have been printed out separately for attaching later

 

Cheers

 

Rob

 

 

 

CAD Model below

 

 

 

 

 

 

 

 

[markjj]

Premier do a chassis to suit the N7 and Slaters will do a motor gearbox that will fit I'm sure. If you look on Slaters downloads page you will find 1:1 drawings of the motor/gearbox combos that they sell which you can print out and try on your drawings. 

[doilum]

If you go down the my path of printing a chassis you need to allow for brass wheel bushes rather than axle thickness. Don't forget to think about pick ups.

If split axles were available commercially Walsall Models cast wheels would be the way to go collecting current through the axle bushes.

Personally for a first attempt and to do justice to the excellent body, I would recommend the Premier component route. Their frames should come with pre drilled holes for brakes and Slater's pick ups. If nothing else they will show you how to go about scratch building brass chassis in the future.

 

[woko]

30 minutes ago, doilum said:

If you go down the my path of printing a chassis you need to allow for brass wheel bushes rather than axle thickness. Don't forget to think about pick ups.

If split axles were available commercially Walsall Models cast wheels would be the way to go collecting current through the axle bushes.

Personally for a first attempt and to do justice to the excellent body, I would recommend the Premier component route. Their frames should come with pre drilled holes for brakes and Slater's pick ups. If nothing else they will show you how to go about scratch building brass chassis in the future.

 

 

Thanks Doilum, some great info there! How you finding printing the chassis for the loco? Its working well? Do you end weighting the locomotive? But thank you for the information much appreciated

Edited April 1, 2023 by woko

[hayfield]

14 minutes ago, woko said:

 

Thanks Doilum, some great info there! How you finding printing the chassis for the loco? Its working well? Do you end weighting the locomotive? But thank you for the information much appreciated

 

 

Can I say firstly what a super loco you have printed, I have no doubt you may well be able to design and print a chassis, but as you were going to use a RTR chassis why not save time and money in buying a set of frames from Premier Components, I understand coupling rods are included

 

https://www.premiercomponents.co.uk/pages/premier-components-lner-locomotive-frame-kits

 

By all means 3D print all the additional details required, but at least get the bare bones of the chassis made from a well trusted set of components (the mill coupling rods would probably have to be bought anyway) and have holes for plunger pickups anyway

 

Also invest in a decent motor and gearbox, at the cheaper end Roxey Mouldings have a nice set, more expensive but better (in my opinion) Slaters plasticard sell a super set up

 

Simply save time and perhaps money for a proven system

[hayfield]

On 31/03/2023 at 11:42, woko said:

Hello folks

 

So im guessing I'm possibly going to open up a can of worms here, and ask a bunch of dumb questions so I would like to apologise in advance if you folks get this a lot, but I would greatly appreciate any help you can give me.

So i'm looking for some advice on how to go about building a chassis and adding a motor, wheels and coupling rods for this L77/N7 I have porotype 3d printed. Originally I was thinking of using a Dapol Jinty Chassis, and fabricating a small pony truck at the back! @thegreenhowards Idea which is a sound idea and worked extremely well beforehand when we used the Dapol Terrier chassis for S56/J69.

However I have since printed out the body for the N7 loco, and I have found the motor on the jinty sits far to forward, resulting in having to cut a section out of the boiler up to the first boiler band in order for the motor to fit properly, which in my opinion would spoil the look of the locomotive!

So I am thinking Rob, why don't you just see if you can build/3d print a chassis for this loco instead, it be worth trying out, seeing if i can get it to work!

I know I can source the wheels from Slaters I will need 3 pairs of 4'10 wheels, and a pair of 3'9 wheels for the trailing set at the back, this is as much as I know that I need so far! Not great I know ;)

 

So my questions are:

 

What motor should I go for, a biggie I know, but I haven't a clue about this, and where to start?

Where is the best place to get coupling rods for the N7, I believe Premier Components do a set?

Does anyone know the standard width for a 7mm chassis out of interest for when I start to build this in 3D?

The hole diameter for the axles according to slaters is 4.763mm so making this slightly larger say 5mm would hopefully allow the axles/wheels to run fairly smooth? I could also create some wheel spacers to be set inside the chassis to add further support!

Do I need to add weight to the chassis, and if so how much is recommended and what to use?

Have I forgotten anything or over looked something glaringly obvious?

And is there any previous threads or videos that I can take a gander at that help with a lot of these questions?

 

Many thanks folks in advance an apologies for the Noob question on this but any advice is greatly appreciated here

 

First test/prototype print below, still some cleaning up to do and there are some issues I need to fix, a bit of warping which just needs some supporting columns inside to fix this issue, and some strange chamfering off in the corner that was the result of an unsupported area I believe. All other details have been printed out separately for attaching later

 

Cheers

 

Rob

 

 

 

CAD Model below

 

 

 

 

 

 

 

 

 

 

WOW  !!!  Looks a stunning loco

[Bucoops]

Adding to the praise - that looks superb!

 

If you want the "Rolls Royce" of motor/gearboxes have a look at ABC gears:

 

https://www.abcgears.co.uk/

 

 

[doilum]

Can personally vouch for the Premier Component rods (pay the small extra fee for split rods) and Canon ABC motor gearboxes. It is possible to extract good results from single gear fold up boxes but newcomers benefit from the " perfect out of the box" quality of the Slater's or ABC products. The ABC boxes are available in several different configurations. Look at their website.

Be aware that pony trucks are often not as simple as they look. Narrowing the rear frames maybe required if the loco is to manage curves of less than six feet radius.

[woko]

4 hours ago, hayfield said:

 

 

Can I say firstly what a super loco you have printed, I have no doubt you may well be able to design and print a chassis, but as you were going to use a RTR chassis why not save time and money in buying a set of frames from Premier Components, I understand coupling rods are included

 

https://www.premiercomponents.co.uk/pages/premier-components-lner-locomotive-frame-kits

 

By all means 3D print all the additional details required, but at least get the bare bones of the chassis made from a well trusted set of components (the mill coupling rods would probably have to be bought anyway) and have holes for plunger pickups anyway

 

Also invest in a decent motor and gearbox, at the cheaper end Roxey Mouldings have a nice set, more expensive but better (in my opinion) Slaters plasticard sell a super set up

 

Simply save time and perhaps money for a proven system

Thanks John some good points!

one of the reasons I wasn’t keen to buy an existing chassis is that I currently don’t have the skills to build one in metal. I have been told it’s quite tricky getting the chassis true/square in general so figured it may just be easier to print this? 
however you do make a solid argument, and looking at your link it’s not a great deal extra money wise, considering I need to buy coupling rods 

 

As for motors and gearboxes I’m completely in the dark here, so previous folks experience and advice is invaluable. I appreciate the advice will check out both Roxey and Slaters sets thank you

 

thanks for your advice and help

 

Rob

[woko]

Thank you both @Bucoopsand @doilumi will check out ABC motors and gearboxes also!

And Premier seem the definite way to go in terms of coupling rods much appreciated guys, I have quite a bit of motors and gearbox research to do this weekend now :) 

 

As for the rear pony truck I’m already on the narrowing of the back of the chassis! I noticed this would be an issue when negotiating curves so figured it will have to narrow to allow the back pony truck axle to slide! Much like I built when I made my GNR 8 wheeler brakevan on sliding axles. 
 

Thank you 

 

Rob

[84B Oxley]

Rob

 

The Premier chassis simply bolts together, it is more or less foolproof. The same firm also does a range of motor/gearbox combinations. Be aware that ABC Gears have a very long waiting time these days, although their products are superb. However, the latest ones from Slater's are pretty much just as good, and there is also a firm called MSC who are equally good and offer very rapid delivery. I've used all of them in the past and been very happy with their products.

 

https://www.mscmodels.co.uk/motor-gearboxes 

 

Hope this helps

 

Jeff

[Bucoops]

2 hours ago, 84B Oxley said:

Rob

 

The Premier chassis simply bolts together, it is more or less foolproof. The same firm also does a range of motor/gearbox combinations. Be aware that ABC Gears have a very long waiting time these days, although their products are superb. However, the latest ones from Slater's are pretty much just as good, and there is also a firm called MSC who are equally good and offer very rapid delivery. I've used all of them in the past and been very happy with their products.

 

https://www.mscmodels.co.uk/motor-gearboxes 

 

Hope this helps

 

Jeff

 

Oh OK, the last one I ordered on the 19th October and had it on the 5th November.

[woko]

On 01/04/2023 at 12:34, doilum said:

If you go down the my path of printing a chassis you need to allow for brass wheel bushes rather than axle thickness. Don't forget to think about pick ups.

 

 

Thanks Doilum i just realised i wasnt aware about brass wheel brushes do premier or slaters sell these? Also pick ups i haven’t a clue about either apologies but it is exactly this kind of info im finding is absolute gold dust from you lovely folks on here

 

cheers

 

Rob

[woko]

21 hours ago, 84B Oxley said:

Rob

 

The Premier chassis simply bolts together, it is more or less foolproof. The same firm also does a range of motor/gearbox combinations. Be aware that ABC Gears have a very long waiting time these days, although their products are superb. However, the latest ones from Slater's are pretty much just as good, and there is also a firm called MSC who are equally good and offer very rapid delivery. I've used all of them in the past and been very happy with their products.

 

https://www.mscmodels.co.uk/motor-gearboxes 

 

Hope this helps

 

Jeff

 

Hello Jeff

 

This is fantastic so no soldering involved in the chassis which will be a brucey bonus, i notice Premier are going to Reading in May so i might contact them beforehand and see about picking it all up at the show! I can also pick their brains about it.

 

cheers

 

Rob

 

[hayfield]

Here are some photos of a chassis and parts

 

  A basic chassis that was given to me by a friend left hand axle hole has a spardard wheel bearing

 A pair of tophat wheel bearings

This is a compensated chassis with sprung hornblocks and twin beam suspension

  A packet of sprung hornblocks

 The small hole left of the axle hole has a rubber bung to hold a plunger pickup

  A pack of plunger pickups

A pack of milled jointed coupling rods

 

  Left a cheaper Roxey Mouldings motor and gearbox Right a Slaters more expensive version

 

I have just flooded this reply just to show chassis design is an art in its self

 

You need a good book about building a chassis to give you an idea Iain Rice wrote a good one

 

[doilum]

3 hours ago, woko said:

 

Thanks Doilum i just realised i wasnt aware about brass wheel brushes do premier or slaters sell these? Also pick ups i haven’t a clue about either apologies but it is exactly this kind of info im finding is absolute gold dust from you lovely folks on here

 

cheers

 

Rob

The bushes are available from several sources including Slater's. There are at least two variations in wall thickness depending on the source, so you really need one in your hand before drawing up the CAD. 

Slater's do a self contained plunger pickup that works well with their wheels. Whilst you will find some people with a strong negative opinion there are many others, myself included, who wouldn't be without them. The key to making them work is careful assembly so that they are very free moving and lightweight multiflex wire for the leads so that they are able to "dance" on the back of the wheel.

If you ever graduate to a tender locomotive, investigate the American system using cast wheels insulated one side only. This would be perfect for a printed chassis.

I have included a.few photos of how much " stuff" goes between the frames.second picture is of S112 which has a Canon ABC driving the centre axle. The last picture is Diana my first scratch build on a Mercian Models chassis. The motor is a Mashima 1833(the numbers are the dimensions in mm) with a fold up 40:1 gear set. Probably from Roxey mouldings. In the first photo Diana is on the right.

Apologies for the shaky photos in poor light.

 

Edited April 2, 2023 by doilum

[doilum]

Whilst you are in the mood for information overload a cautionary word about driving wheels and crank throw.

The Slater's website includes the crank throw for each wheel and list one for the N7. The throw is critical for locomotives which featured deep splashers like the N1, N2 and N7. Even with the theoretically correct throw clearances can be tight as the crankpin reaches t.d.c.

This wisdom comes from the well of expensive experience having built the N1&2 and had to buy three sets of drivers.

[woko]

Thanks guys @hayfield and @doilum this is very helpful and giving me a much better understanding of what I need to research and get my head around, and thank you for the tip about Iain Rice's book on building chassis, I have just ordered his realistic railway modelling steam locomotives to help me get my head round it all.

 

Thank you to everyone who replied to this thread I really appreciate all your help and advice, and hopefully I can do this next stage justice!

Although this 7mm modelling malarkey ain't cheap is it ;)

Adding all these bits up, wheels, motor, gearbox and coupling rods, combined with axle bushes, pickups, Couplings, etc we are well north of 200 squid! But luckily the cost of printing the body/Chassis and detail components of which I have now printed out, (will hope to show the progress of that tomorrow) is only going to be the cost of 1 bottle of resin around £20 so that is pretty good!

 

Cheers

 

Rob

 

 

[doilum]

Given the very high quality of the body printing you might consider deleting the solid buffers. The 7 mm community really expects them to work. The Invertrain website has some very well assembled units at very reasonable prices. Ditto handrails.

All in, you should be able to finish a fully painted perfect runner for under 300 pounds. ( 250 in primer) . It is unlikely that anyone could do a commercial RTR N7 below 400.

Edited April 2, 2023 by doilum

[Ian Rathbone]

Your printed loco looks very good but one thing spoils it, in my opinion. The boiler bands are far too thick - in real life they are about 2mm thick so in 7mm scale they would be about 2 thou thick (sorry about the mix of units but in 7mm 1mm in real life is very close to 1 thou on the model). It is best to have no bands at all as a lining transfer is thick enough, and if you are not lining it then a thin strip of Sellotape is thick enough. Another problem with the bands is that they are generally too narrow, as it is virtually impossible to cut transfer lining exactly to scale width, so there is usually a bit of overhang which is unsightly or liable to damage.

 

Ian R

[woko]

Just now, Ian Rathbone said:

Your printed loco looks very good but one thing spoils it, in my opinion. The boiler bands are far too thick - in real life they are about 2mm thick so in 7mm scale they would be about 2 thou thick (sorry about the mix of units but in 7mm 1mm in real life is very close to 1 thou on the model). It is best to have no bands at all as a lining transfer is thick enough, and if you are not lining it then a thin strip of Sellotape is thick enough. Another problem with the bands is that they are generally too narrow, as it is virtually impossible to cut transfer lining exactly to scale width, so there is usually a bit of overhang which is unsightly or liable to damage.

 

Ian R

 

Thanks Ian that is solid comment, I think you are right I have to do some work to make some amendments to this body anyway so It will be no issue to thin these right down on the next print much appreciated sir for your feedback :)

 

 

[woko]

23 minutes ago, doilum said:

Given the very high quality of the body printing you might consider deleting the solid buffers. The 7 mm community really expects them to work. The Invertrain website has some very well assembled units at very reasonable prices. Ditto handrails.

All in, you should be able to finish a fully painted perfect runner for under 300 pounds. ( 250 in primer) . It is unlikely that anyone could do a commercial RTR N7 below 400.

 

This is very true, and when put like that 300 squid is not bad for a loco of this size in 7mm, assuming i don't cock it up several times that is ;) 

 

My first attempt using a donner  Dapol Terrier chassis was this S56/J69 below, and now I have learnt a bit more in the process of building this and 3d printing it  I would like top remake this, or perhaps an E22 instead! The lovely LNER version is curtesy of @thegreenhowards who I printed one for at the club, it was basically his idea to take the Dapol terrier chassis and build off of that!

 

 

 

 

 

 

[hayfield]

10 hours ago, woko said:

Thanks guys @hayfield and @doilum this is very helpful and giving me a much better understanding of what I need to research and get my head around, and thank you for the tip about Iain Rice's book on building chassis, I have just ordered his realistic railway modelling steam locomotives to help me get my head round it all.

 

Thank you to everyone who replied to this thread I really appreciate all your help and advice, and hopefully I can do this next stage justice!

Although this 7mm modelling malarkey ain't cheap is it ;)

Adding all these bits up, wheels, motor, gearbox and coupling rods, combined with axle bushes, pickups, Couplings, etc we are well north of 200 squid! But luckily the cost of printing the body/Chassis and detail components of which I have now printed out, (will hope to show the progress of that tomorrow) is only going to be the cost of 1 bottle of resin around £20 so that is pretty good!

 

Cheers

 

Rob

 

 

 

 

Rob

 

Welcome to the world of 7mm model railways, yes it can be very dear, but on the other hand if you keep a lookout quite often you can find items on eBay or similar sites/ railway shows/swap meets

 

For a start there are several things which you will have to buy regardless of whether you print or buy a chassis

£75 for some wheels, £9 frame bushes, motor & gearbox £42, pickups

 

A Premier components chassis costs £37  a set of milled coupling rods costs £16

 

If you look at what is supplied for £37, save your resin for what it does best. These frame sets are the heart beat of your loco and it needs not only to be engineered correctly, but use materials that will last and not wear out during use

 

"All our Mainframe Kits are fully machined profile milled, brass thickness being 18swg (1.2mm) and come complete with axle bushes, square brass frame spacers and where appropriate, bogie or pony trucks, which include pivot pin, springs and slotted spacers. All holes (including brake pivot holes) are accurate drilled and countersunk for a screw together assembly.

All Frame Kits include rigid coupling rods profile milled 16swg (1.6mm) Nickel Silver (drilled 2.5mm) to suit Slater's crankpins (can be drilled to any size upon request) optional – jointed coupling (lap joint) rods can be supplied upon request for a supplement fee."

 

You can make a simple pick up system without buying plunger pickups, likewise many use ridged chassis without hornblocks. as a first use a bespoke chassis, then once understanding the principal you may well be able to design something a bit more modern

 

Good luck

[hayfield]

10 hours ago, woko said:

 

This is very true, and when put like that 300 squid is not bad for a loco of this size in 7mm, assuming i don't cock it up several times that is ;) 

 

My first attempt using a donner  Dapol Terrier chassis was this S56/J69 below, and now I have learnt a bit more in the process of building this and 3d printing it  I would like top remake this, or perhaps an E22 instead! The lovely LNER version is curtesy of @thegreenhowards who I printed one for at the club, it was basically his idea to take the Dapol terrier chassis and build off of that!

 

 

 

 

 

 

 

 

Rob

 

In 4mm scale I bought a 3D printed and pre-painted SS56 from CDC models designed to fit a Hornby Terrier chassis. The body is super and very good value but with an etched Terrier chassis looks all wrong. I changed it to an etched J69 chassis and it looks completely right.  Thankfully I had the Terrier chassis for another project (a Terrier) so no money lost in my case. But a lesson learnt.

Edited April 3, 2023 by hayfield

[woko]

7 hours ago, hayfield said:

 

 

Rob

 

In 4mm scale I bought a 3D printed and pre-painted SS56 from CDC models designed to fit a Hornby Terrier chassis. The body is super and very good value but with an etched Terrier chassis looks all wrong. I changed it to an etched J69 chassis and it looks completely right.  Thankfully I had the Terrier chassis for another project (a Terrier) so no money lost in my case. But a lesson learnt.

Ahh interesting to know John, I think you make some good points, ones I have heard before about starting with a solid chassis which will pay dividends in the end in terms of robustness! I do fancy having a go, and seeing if I can rise to the challenge of creating a reasonably good chassis base! Most of the fun for me is the building and the challenge/ Last year I finished a bunch of 7mm Howlden 6 wheel coaches, printed all bar the wheels and remarkably they have proven pretty robust so far, so will see how I get on! If it goes horribly wrong..... Premier chassis it is sir ;)

 

Cheers

 

Rob