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Anybody have max and min measurements for the flange? Or just be able to measure the flange on a good crank. Need to find out how knackered mine is and how much material the shop needs to add to bring it back to spec.

thanks in advance.

 

Cheers, Gavin

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A good way of saving this sort of area is by metal plasma spraying.  This can build up the surface without introducing the heat levels that cause distortion..  It is quite common to see this used on c

Ok, off to the garage attic to measure the spare "cracked" crank. This from a 1985 910, history unknown, presumed original to the car. The flange in question is tapered and has a fillet on both s

Having just installed a crank, I reckon 30lb could be in the ballpark. A quick calc, and shipping could be around £100 - £150 depending on ultimate weight/size.

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I do not recall this information being in the the Service Notes. I would expect you will need to measure your end float clearance and calculate what's required to get it back to the specification.

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Wish I could offer help in this as I have 2 cranks which, unhappily, are not easily reached for measurement. Surely one of the several chaps working through engines at this time could take a reading. Fabian? Barry? David? Ian?

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Ok, off to the garage attic to measure the spare "cracked" crank. This from a 1985 910, history unknown, presumed original to the car.

The flange in question is tapered and has a fillet on both sides, so "thickness" is a vague concept. It should not take much bulk metal to resist clutch loads anyway. Your working dimension is going to be the distance from flange to flange spanning the crankcase web, and you have some wiggle room in the form of the different thrush washer thicknesses available. I can't say if my thrust faces have been machined in the past, but mine is about 1.344"/34.16mm.

I do wonder if a welded repair can be "re-repaired" i.e. grind out the old repair and do  better job of building up the journal before grinding to get rid of the apparent cranks from the old repair.  Might ask your guy what he thinks? I never got a second opinion on my crank, as machinists are 80 miles away in Spokane.

Spare Crank Thrust (6).jpg

Spare Crank Thrust (1).jpg

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Hoping to track down someone local with reliable knowledge on these issues, will share anything learned. One further point of focus will be knowing with confidence whether a repaired crank flange will have the strength and resilience needed to endure clutch loads over many cycles.

Cheers

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Thanks Thomas, greatly appreciate you going to the trouble. Those measurements help immensely. Out of interested, do you recall what the shipping cost were on your replacement crank from Gary Kemp?

 

Cheers, Gavin

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I'd go look the shipping charge up, but it would be irrelevant in today's corona virus environment. I just had some carpets sent over, and UK freight quotes were double recent rates.  Maybe if someone could find actual ship shipping rates for such a heavy item and could wait for the slow boat?

China seems to still be offering free shipping on little parcels, which I assume come on container ships, but they are taking 35-60 days to get here with lots of warnings about virus delays.

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I’ve had no problem shipping brake kits internationally, in fact they’ve generally arrived at their destinations faster than pre-Covid days.  But a crankshaft is significantly heavier and will require a substantial box, perhaps wooden construction. That said you only need a weight and box dimension estimate to get an idea of the cost. I don’t know what a crankshaft weighs, though. Anyone?

Margate Exotics.

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20 - 30 lb. I'd wager. Any crankshaft must be crated very carefully for shipment, wouldn't do for it to be tweaked via rough handling. Still digging for advice through other channels on this.

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Just reviewed a thread I posted over on an American site for gearheads, advice given there includes adding supplementary thrust bearing at another point along the crank. This would entail fly-cutting a register into the flank of the block webbing at another main location and, if I recall correctly, Lotus did not afford excess material which might accommodate this. On welding, another chap opined that very carefully done work could likely result in crazing which, in his experience, did not propagate into cracks.

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23 minutes ago, drdoom said:

20 - 30 lb. I'd wager. Any crankshaft must be crated very carefully for shipment, wouldn't do for it to be tweaked via rough handling. Still digging for advice through other channels on this.

Having just installed a crank, I reckon 30lb could be in the ballpark. A quick calc, and shipping could be around £100 - £150 depending on ultimate weight/size.

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Margate Exotics.

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Custom Thrust Washers

Link above to a chap in the U.S. who manufactures thrust bearings in bronze with a focus on British cars, could be a source for a bearing of custom dimensions. Broadly summarizing our issues, we have need of sourcing some sort of thrust bearing whilst remaining confident of the durability of the block and/or crank should either be re-worked. Latest tip via the other group is nickel-bronze braze welding as alternative to full-on welding, though I'd wonder whether the lay-up would be incompatible with likely bearing washer material. The quest continues . . . 

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My 39 pound (!) crank arrived rolled in about ten layers of corrugated cardboard.  

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I just got a quote through Parcel Monkey and shipping from the UK to the US is approx 310.00 USD

Cheers, Gavin

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Just had a chat with a preferred local engine builder, not altogether a happy one. His view is that nodular iron does not lend itself to welding, though he is not in that end of the business. Will contact other leads found on the web and report here. Gavin, did Lotusbits have used OEM cranks for sale? I reached out and Mike replied in terms of steel replacements.

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Steve......
 
Gavin
 
I have a good block in stock - £600 or £800 fully vapour blasted cleaned and inspected
 
We also have freshly ground and balanced cranks in stock -£600 with matching bearings £250 which you will almost certainly need
 
Regards
 
Mike

Cheers, Gavin

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I am waiting for Garry Kemp to reply on what he has available.

Cheers, Gavin

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Garry will supply steel cranks at 1600 Pounds, last time I checked, probably about the same deal whether Lotusbits or QED for that matter. One other course of action we might consider is to locate a custom bearing on the aft flank of the center main saddle if grinding a face on the crank throw is viable. Cost of this TBD as well, so if expensive then replacing the crank would be preferable. My donor block suffered a wee bit when the washer was spit loose into the sump like a twisted pretzel, so need to examine that for remedy.

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Two conversations this morning, the first of which leaves me less optimistic for salvaging my crank. A machinist with a regional shop dealing in repair of heavy equipment by way of plasma, among other methods, advised of 2 concerns: turbulence of the #4 counterweight affecting spray delivery, and breakout of the weld material as not confined by a ledge at the margin of my smoothly faced flange. That said, automotive work is not their forte so I was off to call number two with a well established local engine machinist firm. Productive discussion there must await the coming week when a semi-retired chap who's the import car guru will be in shop.

On reflection, taking a number of involved measures in machining up a crafty solution must inevitably add to considerable cost and this will be weighed against the cost/benefit of a replacement crank. 

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You can not use spray coating on a crankshaft. Metal spray do not bond to the base material, but laser cladding does. And further, the limited heat input by laser cladding will not cause cracks or tensions afterwards. So post heat treatment is not required. 

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Thank you, Lars. Does laser cladding impart strength equivalent to the base metal lost in this situation? Gavin, back to the root cause of this I'm intrigued on how yours came to fail. Early on in the Turbo series Lotus determined inadequate lubrication of the thrust interface, issuing a Technical Bulletin on modifying one main shell edge to provide oil. This was during the dry sump run and, if I recall that correctly, could account for the fail in my donor engine which was from a written off dry sump Turbo. Has your engine had a bearing change over the years? Have you kept the main shells pulled when it was disassembled? Which oil have you been running?

Cheers

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