By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Allendale May 23

Cost and Weight: 3 1/2 vs. 5 gauge

All Topics | Latest Posts

Search for:  in Thread Title in  
Jon Lawes10/06/2018 08:54:22
295 forum posts

As you may have guessed from some of my posts on here I like to plan things ahead comprehensively before I cut metal!

I've been weighing up the advantages of different project types, from Steam Wagons to Traction engines and rail locos. I had thought that it was pointless doing a steam locomotive as I didn't think I had a track near me, then I was lucky enough to find a group 40 mins drive away with a 5 gauge and 3 1/2 gauge track. This means suddenly my preferred project is viable. After a short chat with some of the experienced engineers there I was heading towards the idea of a 5" gauge locomotive (probably a firefly, Simplex or something of that ilk) as the building of a larger locomotive presents something more tangible; more capable of doing work. However I've realised that the larger it is, the heavier it is, and also the more costly the materials. Although its a project likely to span many years I don't want it to be held up on a regular basis through lack of funds.

So my question; is a 3 1/2 gauge locomotive much more cost effective to build than a 5 gauge? Would it be more suitable to making on my Myford? And does the reduced size make things more fiddly for my fat fingers to operate once complete? I have hands like shovels, and not the scale kind.

For two comparable models (a firefly in each size for example) would it be realistic to say a 3 1/2 gauge loco would be 3/4 of the cost to build considering the cost of castings and boiler copper?

Thanks for everyone's help, I'm currently doing a lot of soul searching about this, and since my grandfather died a few months ago I don't have anyone close to me to discuss such topics (leaving quite a void I have to say).


Jon Lawes10/06/2018 19:06:05
295 forum posts

I'll try rewording. Is it vastly more cost effective to go 3.5 inch gauge over 5 inch or are the differences not significant enough to outweigh the disadvantages?

fizzy10/06/2018 19:58:13
1564 forum posts
104 photos

When something is going to take years to complete dont let a small difference in cost be the deciding factor. Machine capacity, boot/trailer capacity and ease of moving it around once completed are key for me. The main noticable cost difference will be the boiler (unless you make your own) but with waiting times of up to two years you can still spread the cost easily. I found 3.5" to be too fiddley for my spades. Ive got a full set of 5" speedy castings somewhere in the workshop but thats another story...

Jon Lawes10/06/2018 20:28:47
295 forum posts

Good points, thank you. Not just manhandling it but storing it too I guess. My mantlepiece isn't THAT big!

I quite like the look of speedy. It would appear every type I look at has equally keen advocates and harsh detractors. I did wonder if a larger 3.5 inch gauge model would be a good compromise; something like a Britannia is more complex but with cheaper castings errors are not quite the earth shaking issue they could be.

Thanks for the food for thought. I'll keep thinking. It may take me longer to decide than to build!

John Alexander Stewart11/06/2018 02:39:44
744 forum posts
51 photos


Ok - MY opinion. Others will disagree, of course.

I like 3-1/2. Reasons:

- strong enough to pull a couple of people;

- light enough to move; easier than a larger gauge locomotive;

- over here (Ontario, Canada) our club uses 5" gauge, but the norm is 4-3/4, so that's a bit of a "bummer", as one can not visit other clubs. You'll not have this issue, of course.

- elevated tracks, if you have it, are fine for either gauge, as reaching into the cab is then easy.

- ground level running - both are not nearly as convenient as larger gauges (7-1/4, etc)

- parts are smaller and easier to man-handle, and machine on a given machine.

- Just finished a 3-1/2" gauge Shay locomotive to Kozo Hiraoka plans - no castings! Beautiful plans....


Now, I do understand that many think bigger is better, and that I'm an odd-ball here. I do like running larger steam locomotives, but have decided that me building one is not in the picture.

I'd hazard to guess that the trend in North America is 7-1/2" (not a typo) gauge, and "diesel" outline, so steam is on its' way out.

I have a 3-1/2" gauge locomotive in our living room; on a bookcase, under a plexiglass top. If it was 7-1/4, it would be twice as long, twice as wide, twice as high, so would most certainly NOT be in our living room! Neither would the same model in 5" gauge - smaller than in 7-1/4, but still too big.

You have to decide what you want, nobody else can do that for you. Whatever you decide, it'll be the right decision.


Hopper11/06/2018 03:13:24
3527 forum posts
68 photos

Depends too on how old you are. Most of us find heavy lifting harder as the years slip by so the 3.5" might be easier to transport, set up etc.

J Hancock11/06/2018 07:44:14
275 forum posts

But even there, be aware the weight of a 3.5" decent size tank locomotive (35kg), won't be so very different

from same gauge Pacific loco only ( tender separate).

Russell Eberhardt11/06/2018 09:05:11
2431 forum posts
83 photos

Weights - 3.5" about 1/3 of 5"

Costs - castings and materials about half.


Jon Lawes11/06/2018 09:11:05
295 forum posts

I'm rapidly approaching 40 (Signal passed at Danger?) but my bigger issue is I'm an amputee. dead lifting heavy items isn't too much of a problem but carrying over a distance is a little more problematic one legged.

I'm still mulling this over between thoughts of fitting in a relatively quick build freelance steam wagon in the meantime (as discussed before on another thread, using a gear/chain reduction on a Stuart Sirius for motive effort, very simple boiler, minimum of castings. Focus on ease of build rather than accuracy in that case).

I'll attend a few more club nights and see what feels "right" for me. I hadn't considered the Speedy before but the more I look at it the more I like it. I guess I want something that has a fair bit of realism but still is achievable by someone with very modest skills. I want to use this as a learning experience, but to such an extent that I'm in my 80s before I get steam up for the first time!

Thanks all,


Jon Lawes11/06/2018 09:14:53
295 forum posts
Posted by Russell Eberhardt on 11/06/2018 09:05:11:

Weights - 3.5" about 1/3 of 5"

Costs - castings and materials about half.


Thanks Russell, that's a useful guide.

John Alexander Stewart11/06/2018 12:20:08
744 forum posts
51 photos


Another 2 points

- a decade or two ago, visiting the Waushakum track in the USA, I was very impressed with a Kozo Climax locomotive, built by a fellow wheelchair-bound;

- had a very good build log of a Kozo "new" Shay, by Chris Rueby (Crueby), built on Sherline equipment.

Here's a link for the New Shay build - but you may have to register to see photographs(?):


All small and light; it may give more ideas of what would work best for you.


Jon Lawes11/06/2018 12:26:10
295 forum posts

Thank you, I shall investigate.

julian atkins11/06/2018 23:28:59
1196 forum posts
353 photos

Hi Jon,

I shall not waste too much time over this because you really ought to get more actively involved in your local club and get to drive a few miniature locos before you decide. And assist as best you can in unloading them and loading them in other members' cars etc.

LBSC's 'Speedy' 5"g design one could write a lot about. It is an old design hastily done with poor drawings and a defective valve gear. The valve gear has been corrected by Don Ashton.

I will trot out my usual advice for tyros not to build a loco with piston valves or a tapered barreled belpaire firebox boilered loco. The latter excludes 'Firefly', and the former also excludes other designs. 'Speedy' falls into both categories.

I agree that considering the long timescale of a build, cost should not be an issue especially if you plan ahead.

My own advice would be to build a 3.5"g LBSC 'Maisee' with the original boiler not the later combustion chamber boiler. Don Young's 3.5"g LMS 4F is also a good contender. My own first loco was Don Young's 5"g Railmotor which in my case was a modified Railmotor No.2 chassis with a No.1 boiler.

Don't try to lift any miniature loco on your own. I injured my back in 1995 doing this. With your disability, don't even consider assisting, and get others to do this for you.



Jon Lawes12/06/2018 09:13:13
295 forum posts

I've probably overstated my leg issue; my day job involves clambering over large helicopters so I'm not quite as bad as all that, but its good advice regardless.

I can see the advantages to maisee (specifically with regards to the simpler boiler and slide valves) but I think its the two driving axles that put me off. The LMS 4F does look right up my alley however. Don Young's work does seem quite positively spoken about. That looks like a prime contender.

Thanks for the tips, I will also keep attending the club nights. I wouldn't dream of asking to drive other peoples locomotives however, I just couldn't bear the risk of causing damage to someone's pride and joy.

Jon Lawes13/06/2018 09:19:51
295 forum posts

Just as an update I have been researching quite exhaustively, based partially on the suggestion here of tackling Don Youngs 4F (thank you Julian) and the good feedback I have been reading I think the current top contender is the SR Q1 that Nick Feast developed from the 4F (3 1/2 gauge). It appears to hit every spot for me, especially my love of the underdog! Cracking bit of kit unloved due to its unpalatable looks, and so crucial to the war effort.

Obviously this isn't set in stone but gives me a good insight into a route to take. I'm going to purchase the drawings come payday to see what I'm up against. My only mild concern is that only one company offer castings, but I don't see this being a big issue.

Thanks to all that offered advice, it's been great food for thought.

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Latest Forum Posts
Support Our Partners
Eccentric Engineering
Eccentric July 5 2018
TRANSWAVE Converters
Allendale Electronics
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest