Prepared by Steve Luck Originator Toto

Toto - Dec 17, 2017 at 8:07 PM
I have a couple of Steve Beatty kits. One is a class 22 and the other a class 24. I have heard about Delrin drive sets and wonder if these would be suitable for these kits. If so, where could I buy them?
Many thanks for any time taken in response.

Watson4951 - Dec 17, 2017 at 9:31 PM
Have used Delrin drive in all my diesels. Methinks you will get them from Branchlines. Suggest you consider some form of tensioning device as you build. If these are the original resin kits most strongly advise metal inner frame of some sort. Have dealings with resin Cl24. Lets describe it as “interesting”. I could build another, but would not rush to do so!!

Toto - Dec 17, 2017 at 9:59 PM
Many thanks for the feedback. Both kits are of brass construction so I don’t know if that fairs better. I am interested in the comment on tensioning devices though. That is a new one on me. In saying that …….. so is kit building. I have a number from various manufacturers so may start with something a bit easier but as far as the Steve Beatty examples go, the Delrin was jumping out at me.

Booth22454, Dec 17, 2017
You could try below, I have purchased Delrin from them using eBay. Business name: Leisure and Hobby Supplies

Address:Steven Hodgson
Hen Efail, Golan
Garndolbenmaen
Gwynedd
LL51 9YU
United Kingdom

Email:steven.b.hodgson@gmail.com

Chapman16566, Dec 18, 2017
As per Traders' Websites see www.modelrailwaywagons.co.uk for Delrin and timing belts.

Bob Alderman, Dec 18, 2017
Best place I've found to purchase Delrin sprockets and chain is Motionco. They are in the Traders list. Prices are cheap and they clearly detail the dimensions of the sprockets - 1/8“ and 3/16” bores.
Makes it easy to choose. Delivery is fast.

Watson4951, Dec 18, 2017
Ref delrin chain, when it wears you can take a link out. Cant do that with a belt! On tensioners, when you use delrin, it will either not quite reach or you will have an unsightly & unrealistic loop trailing where it can be seen. I have made up slipper plates as required in the form of a very flat [ u-shape. Ends to cover at least 45 degrees and polish smooth. A piece suitable oddment attached to the side with your chosen captive nut. A suitable slot drilled/ filed to suit at mid- point between the respective wheel sets. Adjust as needed [not too tight] and you have a chain tensioner. All can be made up of scrap oddments. Guess how I know these things!!!

Davison16295, Dec 18, 2017
Hi Toto, don't overly worry about putting a tensioner in the system, you shouldn't need it if you set up correctly. the chain should NOT be tight in the first place, rather have a slight amount of slack.( think bicycle chain) The tooth profile of the sprockets is sufficiently large to obtain correct engagement. As You are probably aware Delrin chain is an engineered plastic and is effectively self lubricating as are the sprockets. I have a delrin chain drive on a DMU that I built some 8 years ago, it runs most club afternoons and has not yet had a single link taken out of the chain, nor in fact has it been lubricated. The toothed belt that someone has mentioned is very like the car industry switching to belts from chains and look what happened there !

Sandy Harper, Dec 19, 2017
As fitted to a Class 20 bogie. The Delrin cog on the gearbox axle had to be modified to fit.

Bob Alderman, Dec 20, 2017
Problems of longevity with Delrin drive.
I have several locos with the drive, some of some antiquity now. The material still shows no signs of distress. The only problems I have had is where oil from the motor/gearbox has contaminated the chain. This has accumulated “dirt” that has gagged the chain. Remedied by a blast of aerosol IPA blowing the crud away followed by a re-lube of the metal bits. The gearbox has benefitted too.

SteveHoather, Dec 20, 2017
I use abc gearboxes and Delrin drives on all my recent diesel locos. In the case of Co-Co locos I drive only the outer wheels, making them in effect A1A-A1A, but otherwise the arrangement is very similar to that shown in Sandy Harper's photo (#22). As I run 12 coach trains at realistic speeds (90 mph) and up a 1 in 50, I power both bogies to get sufficient adhesive weight.
My oldest loco with Delrin, but different motors, is about 25 years old and still going strong. I do not use tensioners, the key is to get the axle spacing so that the Delrin tension is just right at build. Since the bottom length of Delrin sags quite a bit when running in one direction, I fit a plastikard shield to the bottom of the bogie so the drive does not foul the track - more likely on a 6 wheeled bogie.

Sandy Harper, Dec 22, 2017
The Delrin Sprocket has a short flange on one side and a longer one on the other. Depending on your installation, you may need to trim back the longer flange to make it fit in the space you have available. Watson 4951 suggests that it would be better to reduce the length of the axle top hat bearing, on the inside of the chassis frame, to gain the additional clearance rather than shorten the flange of the Delrin sprocket as the Delrin sprocket is a interference fit on the axle and reducing the length of the total flange width may compromise the 'grip' of the Delrin with the axle and cause the sprocket to slip under heavy load.

On my installation (See photo above) I needed to to trim back the axle bearing flush with the inner chassis side, and also remove a couple of mm from the Delrin sprocket, to get it to fit in the space available between the gearbox side plate and the inner chassis side. If needed some Nutlok could be applied sparingly to the Delrin sprocket to secure it to the axle but I have not found this to be necessary as yet.

SimonD, Dec 22, 2017
I’d be wary of using a nutlok type adhesive on a joint between a plastic and a metal. These products increase in volume on polymerisation, and could adversely stress the plastic. It’s certainly not recommended on the Loctite applications guidelines.

Having said that, I’m aware of many cases where it has worked without issue. I guess it will depend on circumstances.

I guess it would be possible to pin the sprocket to the axle if further torque capacity is required?

Buckley10339, Dec 22, 2017
On my DJH 9F that uses a Delrin drive from the gearbox to the center axle i am going to drill through the Delrin gear and axle and pin it. The Delrin gear on the gear box is done already like that by DJH as its their one specially for the 9F.The motor used is a very powerful huge Buhler same as on the MSC Crailcrest unit with an awful lot of torque so pinning the Delrin gears is a must especially as i am intending to try a very long rake of wagons on it at some point - at least 50 if not more!

DavidL, Dec 22, 2017
Sandy,
Thanks for your explanation at #31; that's now a lot clearer. BTW, whether or not anaerobic’s are suitable for the job (and I've not found them to be a problem) I don't think the Nutlock grade would be the one to use. That grade is designed to give easily under moderate torque; it stops nuts from vibrating loose, but allows them to be removed with a spanner. I suggest the standard retainer grade, or even the high strength grade, would be best.
Simon,
I can't find any reference to anaerobic’s expanding on curing; do you have one? I know they work by polymerisation in the absence of oxygen, to form a Perspex-like plastic which gives an interference fit, but polymerisation does not usually cause expansion.

If problems do arise, I'd be more likely to suspect some chemical interaction with the plastic; maybe absorption into the part, which I suppose might cause expansion of that.

Jim Snowdon, Dec 22, 2017
More pertinent is the fact that Delrin, from which the sprocket is moulded, is extremely difficult to bond with adhesives. Getting any adhesion depends on the use of distinctly exotic surface treatments that are well beyond the capabilities of the home workshop. Hence the use of mechanical fixing methods such as splined axles (and we all know the problems that can occur with that method) and cross-pinning.

Bob Alderman, Dec 22, 2017
SimonD said:
I guess it would be possible to pin the sprocket to the axle if further torque capacity is required?

Yes it is. It and the axle drill freely. I use copper wire and bend short ends away from the sprocket teeth to avoid possible interference with the chain.

ChrisSimpson, Dec 22, 2017
There was mention of the chain sagging, and I had this situation on my Triang Big Big Hymek, which I converted to 'more like' scale using a RJH conversion kit. The chain sagged, and I could not remove a link to eliminate it, so I made up an idler to take out the sag. It is just a turned pulley running on a shaft fixed to one of the side frames.