Derlin drive

hornbeam · Jan 24 2018 13:03

Afternoon,

I'm planning on using some derlin drive chain in a project to transfer from a steam unit to he driving wheels. I don't plan to use it to gear down at all. The sprockets come with the option of differing amounts of teeth. Should I just go for all 8 tooth, or would say a ten tooth wear less?

I maybe asking a really silly question but guidance would be much appreciated,

Thanks
Simon.

Spitfire2865 · Jan 24 2018 13:11

From an engineering perspective, more teeth meshing with the chain means more torque can be applied across the chain, up until the chain or teeth yield. Unless youre expecting considerable forces and accelerations with this setup, I dont see why 8 tooth wouldnt work, but if you have the space, use as big of a gear as you can for reliability and strength.

hornbeam · Jan 24 2018 13:53

Perfect thanks Trevor. Because replacement will be very hard after assembly the less wear the better. I'm pretty sure I can accommodate larger gears so that's what I shall do.

Thanks again

IanT · Jan 24 2018 13:57

Yes Simon, I'd certainly agree with Trevor - within reason a larger toothed wheel would be preferable.

Some other thoughts on 'chains' might be useful (please disregard if not!)

We spent some time looking at 'chains' when designing the Sentinel 100HP. We did find a very small scale 'roller' chain (I forget the actual pitch size off-hand) but it was very expensive, even when purchased directly from China. I have some small (but larger than Delrin) roller chain, which I think is normally used as motor cycle 'timing' chains - but it was considerably out-of-scale for the Sentinel (where the chain is very visible). I was initially concerned about the strength of the Delrin chain (which is widely used in 16mm circles) but it certainly seems fine on the two prototype engines that have been built thus far.

This photo was taken when John, Mike and myself were discussing the subject and shows the Delrin chain vs the size of the M/C timing one I had (compared to a G3 wagon wheel castinng). The Delrin is considerably finer and very near 'Sentinel' scale in fact.

However, if your drive train is out of sight, then a larger (steel) chain might be preferable - and if you can find a suitable small chain (motorcycle spares?) then the sprockets would not be too difficult to make (essentially indexed drilling of a suitable plain disk, after which you'd turn the disk down to max tooth height and then file the teeth tops). Sounds complicated but in practice much easier than cutting involute gears I think - and no expensive cutters required. I have the required 'math' somewhere if you are interested.

Regards,

IanT

hornbeam · Jan 24 2018 14:45

Thanks Ian,

Most interesting. Well I am building a live steam Sentinel. To cut a long story short I wanted to have another live steam engine but on a budget. My initial plan was to use a GRS steam motor and design some frames and use slaters wheels, along with Roundhouse 'uppers' this was stopped in its tracks by the fact GRS no longer sell said unit.
The amount of work in using Roundhouse cylinders etc would be beyond me. So I have ended up buying a set of etches for the LNER Y3 from the shop. No castings included. I will make the frames and source wheels etc and plan on using cylinders from a 16mm supplier roy wood steam models ungeared as they are powerful enough for what the prototype pulled. If I get it right both axles could drive from this if its dead centre in the wheelbase like the real thing. If not I'll drive one axle from it and then a chain to link the other axle from this so it may well end up visible.

Thanks

Simon.

IanT · Jan 24 2018 15:08

I didn't realise it was a Sentinel you were planning Simon.

As it happens someone else is also thinking of building a live steam version, although not with the etch you mentioned (that I am aware of). I've supplied some GA/CAD to them but there was also a suggestion that Mike W might be able to help with some of the small (cast) fittings that were used on the two B/E engines already built.

So if you have not already - it might make sense to ask Mike what is already available (or planned) that might help your build.

Regards,

IanT

hornbeam · Jan 24 2018 15:15

Hi Ian,

Already have done so. I think wheels and wheelbase are different but that's no issue. For me it was more about the buffers and axle boxes. I should add I'm planning on using a Regner boiler and fittings as they do a boiler off the shelf that will fit. Interesting that I'm not the only one doing one, even more so as the shop said they stopped making them as they didn't sell. They also mentioned as soon as they discontinue something people want it!

IanT · Jan 24 2018 17:17

Sorry Simon - missed the reference to Y3 - brain was firmly fixed in 100HP mode...

The other guys are of course looking at the 100HP Sentinel...

Regards,

IanT

hornbeam · Jan 24 2018 20:15

Sounds an interesting project and would be keen to know more if possible?

IanT · Jan 24 2018 22:40

Yes, I think it will be a very interesting project Simon.

Actually, now I think about it - I'm not sure if it's been discussed on here before (I haven't checked), so perhaps I should leave them to decide when they are ready to talk more about it.

Regards,

IanT

John Candy · Jan 25 2018 08:34

Yes, person involved is a (relatively) new forum member but their Sentinel proposal has not been discussed here, as yet.

They will be at the G3S AGM (with a trade stand for their other projects) so there will be an opportunity for discussion at that time.

John.

hornbeam · Jan 26 2018 17:29

Thanks Ian and John, all fair enough wouldn't want to step on anyone's toes.

Looks like the shop has found a full set of castings so that will help. Now need to draw up the frames and get some spacers made.

andrewfoster · Feb 15 2018 03:54

If possible, it would be good to check a sample of the chain first. A few years ago I bought a supply of 1/4" pitch Nylatron chain - very similar to the Delrin type - for the GME bascule bridge drive, and found that there could be interference between the links, particularly running round the smaller sprockets. Fettling them to get a smooth drive was exceeding laborious. The advice to use the largest possible sprockets is good and will help. It's strong and works really well once you get it right. (I have more than I'll ever need, so if anyone would like some for a very modest price, please let me know.)

Andrew

Andy Mould · Feb 22 2018 11:29

Ah well I should stick my head above the parapet, I have unfortunately quite busy of late so haven't been following the forum, but yes it is Dad and I who have been looking at building a couple of post war 100hp locos in live steam, but as yet no materials have suffered in the name of engineering!

Our biggest concern is boiler size and water capacity the capability of the delrin chain hasn't really reared it's head but from my experience in G1 I don't think we would have an issue, however that's now taking into account what the affect of heat may have.

Our effort will be much more based on what we can fit in as it's largley going to be a model engineering effort by Dad now he is finally retired and was looking for something else to do as he is just finishing off a couple of G1 locos so I suggested this project in G3, supported by my design work, especially as I have plenty of other projects now up and running in G3.

hornbeam · Feb 22 2018 20:31

Thanks for the info Andrew. And sounds an interesting project Andy! Please keep me posted on how it goes

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