Rods and generator

[BrianReynolds]

Learned gentlemen, I am just about ready to assemble the engine for my '57 S4. I plan to recondition the existing con rods ( as the AOMCC rods are currently unavailable for the foreseeable future, unless someone has a set they don't need?) Is the original size of the large end in the rod exactly 1.500" ? I own and operate a commercial machine shop so no problem to do this. Also, I would like to convert the bike to 12V electrics, any way to do this without major engine changes? Many thanks,

[john.bebb]

Hi Brian,
Dimension / tolerance of big end eye is given as 1.5002 / 1.5007 (no temperature specified - assume 25C).
see https://www.draganfly.co.uk/ariel/4-str ... nd-1937-58
Best option for 12V electrics is to fit https://ironhorsespares.co.uk/square-four-alternator/
This is simple retro-fit & gives 300W max power output - far superior to the Alton alternative.
Cheers, John

[paul.ptak]

The manufacturer of the new rods states the big end size as 1.4999 - 1.5004.

Manufacturer quoted me 4 weeks to produce the rods; my order is supposed to arrive next week, making the total lead time 3 weeks.

[BrianReynolds]

Thank you Paul, do you mind passing on details of where you ordered the rods? I checked with the usual suppliers and was told it would be "the end of the year" before any would be available. Thanks also for the info on the L/E size. This is my first Ariel rebuild so I haven't got the inside track on suppliers as yet.

[Vincent.vanGinneke]

Is Alton making SQ4 dynamo's (generators) ?

[roger.fellows]

Bennet Longman for an alternator. ?Iron Horse spares?

[paul.ptak]

Thank you Paul, do you mind passing on details of where you ordered the rods? I checked with the usual suppliers and was told it would be "the end of the year" before any would be available. Thanks also for the info on the L/E size. This is my first Ariel rebuild so I haven't got the inside track on suppliers as yet.

https://www.rrconnectingrods.com

I found the manufacturer of the rods in this thread -

http://forum.arielownersmcc.com/viewt ... =4&t=10344

[john.bebb]

Hi Peoples,
I find it somewhat disconcerting that the "manufacturer of rods" & the SAME devices as may be obtained via Drags &/or from Bruce Longman are actually quoting DIFFERENT specs for the big-end eye...

Ultimately this dimension & tolerance should be determined by the dimension & tolerance of the big-end shells.

Sure - the two quoted dimensions for the big-end eye differ by only 3/10 of a thou" - but in a precision fitment which is likely to undergo stresses upward of 50 tons per sq" in regular use such clearances become most relevant in a rotating pivot that may well wear itself out before it has even run itself in...

My suspicion is that the "manufacturer" data is in error - perhaps Drags & Bruce should communicate with rrconnectingrods to clarify dimension and toloreance.

There CANNOT be two "correct" dimensions for the device!

[BrianReynolds]

Thanks for the insight. To be honest after reading the forum there appears to be potential issues with new rods in terms of actual fitting, some claim the new rods are tight and have to be reamed or honed to fit. There is also some discrepancy in the actual sizing, albeit very fine tolerances, not to mention potential balance issues. I am a machinist with over 45 years experience and currently own and operate a commercial machine shop, so I have some insight into what is being discussed. After reading everything I can find concerning the rods I have come to the conclusion that the Mk2 rods in my 57 S4 are probably up to the job, at least as much as any other component within the motor. The bike has only 9000 miles showing, so I don't think fatigue should be a problem, I think the only severe fatigue will be in my body if I ever get it on the road ! My current plan is to recondition the rods and install new bolts. I will test fit the new bearings and measure for journal clearance, if that looks ok, then its going back together. it would be helpful if there was clarity on the actual L/E rod size, the original tolerance of 0.0005" appears to be excessive and may well reflect the limits of the manufacturing processes 63 years ago. In the absence of solid information I will set the rods at 1.5002", ( generally 0.0002" is an acceptable tolerance on other rods ) fit the bearing shells and check clearances. It is straightforward to increase or decrease as necessary. Thanks,

[john.whiting]

I believe the dimensional variation being complained about originally is in fact of the order of .003" undersize,not a few tenths.And as Mr Reynolds says,a newish quality CNC machining centre can hold a tolerance of 2 tenths day in day out,one with a few millions parts on the clock may not......New machines are used to make aeronautic parts and the like ,older machines to a do a run of a few dozen conrods for a motorbike.