Lotus Elan

odds and ends!

PostPost by: worzel » Thu Jan 12, 2012 12:46 pm

Some technical info wanted plus opinions-

Firstly, given sufficient expertise on the part of the operative, is it possible to satisfactorily weld cast iron? The altered/repaired part won't be subject to stress eg an engine block but will simply be bolted to another component. No sideways stress/loads on it?

Secondly- anybody out there got handy access to a 4 speed clutch friction plate- I'm looking for the following measurements- overall length of the splined centre and
how far above the face of the linings on the flywheel side do the splines protrude?

Third- a friend (new to elan ownership) is considering a 5 speed conversion but doesn't want to get involved in altering the oily bits himself. I could do it for him (rework the linkage etc) but to be honest it's a lot of effort and pretty time-consuming so I've bowed out on this one. Have agreed to help him fit it though so haven't quite abandoned him.

He's considering the Alan Voights kit which I've got to be honest isn't actually all that pricey when considering it's a "drop in" conversion. What he doesn't want though is a conversion like mine which doesn't have any spring loading against 5th- I "fish" from 5th to 4th but you soon get used to it- he doesn't like it at all. So what I'm asking (from those with a kit fitted- preferably some time ago to see how it stacks up long term) is does the AV kit have some sort of spring resistance against 5th so that 5th to 4th is simply a "pull down" affair like it would have had when fitted to Fords or does it use some sort of "cam" arrangement? Related to this- what's the opinion on how the box works in terms of precision of gearchange, any baulking when swapping gears etc?



Regards and thanks

John
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PostPost by: nebogipfel » Thu Jan 12, 2012 12:59 pm

John

With reference to cast iron it's perfectly possible to weld cast iron using the correct techniques.

That said I have successfully brazed cast iron in the past and that might be sufficient for what you have in mind.

Interestingly some of the modern cast iron items such as those used in decorative items such as gates etc will mig weld with no problem. It's all in the crystalline structure apparently.

Cue the metallurgists on the forum .............
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PostPost by: bcmc33 » Thu Jan 12, 2012 4:38 pm

With reference to cast iron - it's possible to 'perfectly' weld cast iron.

I have to admit I've never actually done it myself, but in a previous lifetime as a plant engineer, the fitters would often have the need to repair or modify CI based machines. They did it by heating the CI in the area to be welded with oxy/acetylene until red hot, and then MIG weld. It always seemed to work perfectly - but then they were skilled people.
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PostPost by: nebogipfel » Thu Jan 12, 2012 5:17 pm

bcmc33 wrote:With reference to cast iron - it's possible to 'perfectly' weld cast iron.

I have to admit I've never actually done it myself, but in a previous lifetime as a plant engineer, the fitters would often have the need to repair or modify CI based machines. They did it by heating the CI in the area to be welded with oxy/acetylene until red hot, and then MIG weld. It always seemed to work perfectly - but then they were skilled people.


Yes welding cast is a specific skill. (I don't have experience of it) But it's all about controlled cooling of the job to avoid stresses building up within the crystalline structure causing cracking as the job cools.

As I understand it in the good old days the job was brought up to temperature, welded with special cast iron rods (Arc welding) and then the cool down was carefully controlled too, in an oven I think.

I have mig welded small cast items successfully and have also brazed cast (as I mentioned previously).

I am sure things will have moved on these days ....

That said, you will often find that agricultural engineers have a fair bit of experience welding cast iron.
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PostPost by: elj221c » Fri Jan 13, 2012 1:49 pm

worzel wrote:
Secondly- anybody out there got handy access to a 4 speed clutch friction plate- I'm looking for the following measurements- overall length of the splined centre and how far above the face of the linings on the flywheel side do the splines protrude?

John


John,

I have one of these (in the cupboard under the stairs!); http://qedmotorsport.co.uk/qed-shop/lot ... ompetition

The spline hub measures 25mm and the height above the friction material is 3mm on the engine side. However, if you look at the picture on the QED site you will see that the plate is provided by Helix. Their information quotes 22.5 mm length. I must say that I bought my plate in 2004 so there may have been changes or they may be refering to the actual length of the spline because there is a chamfer on both sides of the splined hub. I can't realy measure that acurately so I hope you get what I mean. Pictures to help.
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Clutch engine side.JPG and
Clutch.JPG and
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PostPost by: worzel » Sat Jan 14, 2012 12:06 pm

Hi Roy and others

Thanks for the info- that'll help with number crunching.

No comments yet on how the Alan Voights conversion works?

Regards

John
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PostPost by: UAB807F » Sun Jan 15, 2012 8:43 am

worzel wrote: (part quote)

Firstly, given sufficient expertise on the part of the operative, is it possible to satisfactorily weld cast iron? The altered/repaired part won't be subject to stress eg an engine block but will simply be bolted to another component. No sideways stress/loads on it?


Yes John, it is. As the others have said, it can be done but not as easily as welding mild steel. It's a long time ago since I looked at this but from memory the main arc welding rods were basically a nickel alloy rods, and the alloy formed during welding had sufficient flexibility to hold it together.

At the risk of boring folks (or making mistooks due to faulty memory) you can consider CI as mild steel with loads more carbon present in the structure. The original CI ("grey flake iron") has this extra carbon is present as graphite flakes all over the structure. (imagine looking down at a plate of spaghetti, the flakes are the spaghetti) This is what causes it to be brittle because it will fracture across the graphite flakes rather than the basic iron structure - it's like a weak link.

So after welding it (assuming you manage to get it to stick in the first place) as it cools down these graphite flakes go under shrinkage stresses and sometimes it goes ping. With steel you don't have the same weak graphite flakes present, so it stays together after welding with no problem although the shrinkage stress might cause distortion.

By using a filler metal that can absorb some of these stresses (eg Nickel alloy) you have more chance of it working. I've even heard of people peening welds with a hammer as they cool, which sounds odd but they are trying to form compressive stresses in the surface rather than the tensile stresses due to contraction.

The other main player with CI is often called Ductile or spheroidal graphite iron (DI/SG). This has roughly the same amount of carbon, easy to cast, etc, but the heat treatment & other elements allow the carbon to form in what look like balls across the structure. This is good because you get cheap, castable iron but without the weak-link graphite flakes so it's much tougher than grey flake. I'd guess this could be easier to "weld" simply because the structure can absorb more cooling/tensile stresses.

I'd guess if you get a welder who can weld CI one day and then fail miserably the next, it's not his lack of skill but the difference in the irons. It's not easy to tell from just looking although you can do simple comparison tests like looking at grinding sparks.

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PostPost by: ardee_selby » Sun Jan 15, 2012 11:46 am

http://www.castironwelding.co.uk/Cast_i ... ntage.html
http://www.castironwelding.co.uk/cast_i ... ocess.html

These folks seem to have the answer. The controlled pre-heat may be the key for complex casting sections.

But I'd like to know how the nodularity in the SG welding zone is achieved :?

Cheers - Richard
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