Cylinder Material

[ron]

Hi All
I was browsing through Reeves price list for 'Simplex' parts and noticed they did a choice of gunmetal or CI cylinder castings, the gunmetal ones being nearly twice the price of CI, I was curious to what the pros and cons were of the two materials considering the large difference in price?
Ron

[swgwm02]

Cast iron cylinders tend to cheaper but are slightly harder to machine and require tungsten carbide tooling etc. With properly fitted piston rings they can give many years of service.They are however prone to rusting if left for long periods without oiling up first.
Gun metal cylinders are generally more expensive,they can be machined with high speed steel bits and are easier to machine.
Most gun metal cylinders use soft packing in the pistons,which is normally graphite inpregnated string.
Although not be as long wearing as cast iron this is debatable as many old models which have been used regularly are still running and the ones I have looked at have hardly any wear at all.
Apparently piston rings made of ptfe can be used in gun metal cylinders but I have no experiance about these.

[Donald G]

I have fitted PTFE piston rings to my 5 " 13xx tank locomotive. They have an 'O' ring at the bottom of the groove, and the split ring fitted above, once bedded in, they have giving good running, and are certainly worth fitting with gunmetal cylinders. There are a number of locomotives running in our club with these rings. When my 3 1/2" Rob Roy comes in for service, it will be fitted with 'O' ring and PTFE rings.

Hope this helps,

Donald

[chris vine]

Hi Ron,

Don't worry about cast iron cylinders rusting, I think it is a myth. I have never had a problem, even if the engine is left standing for two years after its last steaming and no special oiling afterwards.

AS long as the lubrication is good, the iron, being porous, will absorb enough oil to protect it.

Personally I like to use Iron with iron rings. With the amount of use we give them they will last for ever and a bit longer.

Cheers,
Chris.

[ron]

Hi All
Thanks for the replies, I asked mainly out of curiosity, my own experience is mainly with Stuart Turner which have CI cylinders which I've never had any problem with although I do give them a short run on air and oil them after running them on steam. I was just surprised at the extra cost of gunmetal, as I said, almost double the price.
Ron

[JohnP]

Donald,

I'd like some information on the PTFE ring if you could. Is the joint scarfed? How thick is the PTFE? I've been thinking of somethging similar for my Metro, I can't get on with this graphited packing.

JohnP

[spurley]

Hi Swgwm02

Is that a fact about tungsten carbide tooling for cast iron? I turned my Tich wheels using a high speed steel tool, a la instructions by LBSC without too many troubles! Maybe I'll try TC on my Mona wheels,

Anyone else care to advise/comment please?

Cheers

Brian

[jgb7573]

High Speed steel works fine on cast iron as you have found. However, you will need to resharpen the tool more frequently and run at lower speeds using it as compared with TC.

[ron]

I think with the price and availability of TCT lathe tooling nowadays it's hardly worth bothering with HSS unless you need a special shaped cutter. I've also recently bought a pile of solid carbide Stellram end mills at a very reasonable price off Ebay, absolutely marvelous, would probably mill concrete. ;D
JohnP, I've made one pair of PTFE rings, they were about 3/32" square, turned from a piece of solid bar and then cut at approx 45 deg with a Stanley knife, they are quite tricky to get right, they swell quite a bit with heat, think in future I would stick with CI cylinders and CI rings.
Ron

[Shawki Shlemon]

HI
I have built many engines and used both CI & Gunmetal , I assure you both are OK .The only problem wit CI these days is the use of recycle metals and one may get a hard spot and that is when one needs tipped tools .As for PTFE I have used a square section ptfe yarn , it is available in many sizes . once fitted is good for ever . The same applies for CI cylinders and CI piston and rings . It is a matter of choice .Generally when I leave an engine with CI cylinders for long time I fill exhaust blast with steam oil , open drain cocks and move the engine for and back a few times until oil comes out of drain cocks , close drain cocks and forget about it until next run .

[havoc]

The only problem wit CI these days is the use of recycle metals and one may get a hard spot

Hard spot is the word. Just heard at the meeting that at a workshop they bought cheap bars and tried to saw them using carbide tipped blades. The carbide just got stripped of the saw... Closer inspection reveald there were still pieces of drills and carbide tips in the iron.

[steamjohn248]

Agree with our antipodean cousin, We ALWAYS put a good glug of cylinder oil into the valve chest, ( through a small plug cock) and then push the engine back and forth a few times with the drain cocks open. On the odd occassion "someone" forgets at the end of a session, there are often horrible squeals next time the engine is moved (this is with C.I. rings in C.I Cylinders).

Steamjohn

[steammadman]

just chesked the cast cylinders on my "bantam cock", it's not been steamed for about 4 or 5 years now, guess what, NO SIGN OF ANY RUST.
W ho says cast iron cylinders rust?.
they are talking out of their hat!.
I have the proof here
no rust

[swgwm02]

Rusting of cast iron etc is dependent on the presence of water and oxygen.Therefore on certain occasions cylinders may have no water trapped in them and will then be less lightly to rust.
There is also some thought that cylinders are sealed and are not exposed to air and this also may inhibit rusting.
Another factor which may vary the amount of rust in cylinders is how much oil was trapped in the cylinder when the loco was last used.
Overall I would tend to be cautious and administer the proverbial squirt of oil just to be on the safe side when putting the loco away for the season. After all it only takes a few minutes and peace of mind is a great thing!
Incidentally I restored an old loco some years ago, which had rusted up cylinders and pistons,the rust had caused deep pitting in the bore. However after much honing and a new set of pistons , all was well.

[ron]

Further to my question about cylinder materials, another one about horn blocks and axle boxes.
I got a belated price list in from Blackgates this morning and they give a choice of CI or gunmetal for these parts, with the gunmetal being about three times the price of CI, is it worth paying the extra for it or would it be worth mixing them with say CI hornblocks and gunmetal axleboxes? any opinions welcome.
Ron

[baggo]

The horns that came with my bits are gunmetal with lumps of cast iron for the axle boxes but given the choice I think I would go for cast iron horns. They are stiffer, cheaper, and, in my opinion, nicer to machine (apart from the swarf!). I believe cast iron works very well with cast iron so you could use cast iron axle boxes as well. The cast iron boxes should work ok with mild steel axles. I intend to fit needle roller bearings to my own Simplex so the boxes will be machined to take these.

John

[ron]

Hi John
The drawings give it as CI horns and gunmetal axleboxes so I'll probably stick with that, I like the idea of roller bearings as well, might give that a bit of investigation..
Made a start today, turned most of the boiler bushes.
Ron