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1100S Large Journal crank Vs 1275 A+ crank
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Author:  Minimad [ Tue Mar 06, 2007 6:40 pm ]
Post subject:  1100S Large Journal crank Vs 1275 A+ crank
Can someone tell me the difference between these cranks and if they are interchangable???

Can the A+ be modded to go in and 1100s block with the 1100s rods??

Minimad
Author:  drmini in aust [ Tue Mar 06, 2007 6:43 pm ]
Post subject: 
only physical difference is the A+ one has rolled fillet radii.
It bolts straight in an 1100S block, with any big journal rods including 1100S `lumpy' ones.
Author:  miniobsessed [ Tue Mar 06, 2007 6:56 pm ]
Post subject: 
It all depends...

1100s motors had a 'small journal' crank or a 'large journal' crank - referring to the big end journal size (1 5/8 - small 1 3/4 - large)

The A+ cranks I believe are all 1 3/4 but I could be wrong.

Something worth considering if you have the small journal 1100s and you're dropping in the large journal A+ is that you can offset grind the large journal to increase your stroke approx 1/8 of an inch :) Offset grind the crank, take a few thou off each side of the rods so they fit the new crank, machine half the increase in stroke off the top of your pistons so they don't stick out the top and then make sure your compression ratio isn't too high :)
Author:  drmini in aust [ Tue Mar 06, 2007 7:10 pm ]
Post subject: 
He's comparing a large journal 1100S crank with a 1275A+ crank (see title).
Both are large journal (1-3/4" crankpins).

Offset grinding a crank that has rolled fillet radii is not a great idea really, but has been done. :wink:

,edit> reason it's not a great idea (IMO) is you finish up with a normal ground fillet 1/2 way round the crankpin and a hollow `rolled fillet radius' for the rest.
The term `stress raiser' comes to my mind.....

<edit 2> here's my 12G1505, 84.33mm stroker crank, after wedging and before final linishing... journal sizes std/std.
Image
Author:  miniobsessed [ Tue Mar 06, 2007 7:32 pm ]
Post subject: 
fair enough... I'll read more closely next time...
Author:  Minimad [ Tue Mar 06, 2007 8:16 pm ]
Post subject: 
Thanks Guys

As you can probably guess from the multiple different threads.. I am considering either replacing the crank ( a 12G1505) with an A+ crank as the tail has quite bad rust pitting.

I know this is a large journal crank, but is the A+ cranks good for a few revs??? This would be to put in my 'race' motor :roll:
Motor is currently running
full steel main caps
Lightened flywheel
lighted and balanced rods with hypatec pistons +.20 (and it's an auto block!)
Kent MD296

Minimad

Ps No stroker motors here...not allowed in historic racing :oops:
Author:  willy [ Tue Mar 06, 2007 8:52 pm ]
Post subject: 
Graham Russell is building my A+.

40thou over.
A+ block
A+ gearbox with Tran-X diff.
Lightened fly
Straight cut drop gears
A+ head with extensive work
A+ crank, wedged and going to be 'tricked up' a bit
A+ conrods, which will be attended to in the weight department.

All the other usual bits, Weber etc etc.
Hopefully should see 120 @ the fly all going well.

I had the choice to go a Small journal, and stroker, but decided that I had already bought enough bits to build up the big J, so I did.

The A+ cranks aren't old and abused, as some small J cranks, so this is a thing to consider.
All of the Mini Seven racers use these, and don't have issues so I that's good enough for me 8)


edit: You entering in Nc class?
Author:  Minimad [ Tue Mar 06, 2007 9:04 pm ]
Post subject: 
Yes Nc racing.

Haven't got there yet... still "practising" in the regularity :oops: Can't see myself graduating any time soon!!

Minimad
Author:  willy [ Tue Mar 06, 2007 9:11 pm ]
Post subject: 
At least you're out there having a go!

I'm still yet to get out there :lol:

Mind throwing up some pics of the Mini?
Author:  Minimad [ Tue Mar 06, 2007 9:37 pm ]
Post subject: 
Image
Image
Image
Author:  drmini in aust [ Tue Mar 06, 2007 9:38 pm ]
Post subject: 
MiniSport UK has A+ cranks on special for £175 I think, with bearings.
But it will cost you heaps in freight etc, as my mate Dave Gray (Nb Cooper S) found out.
Author:  Minimad [ Tue Mar 06, 2007 9:47 pm ]
Post subject: 
Lets try and fix the old one first me thinks........might be cheaper too

Minimad
Author:  willy [ Wed Mar 07, 2007 8:05 am ]
Post subject: 
Fwoor that looks very nice! 8)
Author:  HistoricRacingS [ Tue Mar 20, 2007 5:49 pm ]
Post subject: 
Hi Minimad,

I've just taken out an A+ Crankshaft out of my race motor.

It ran for around 15 meetings before it cracked! Some are good, others not so good.

I broke the end off the previous one second time out!

HRS

PS: Great looking race car!
Author:  Pin4e [ Fri Mar 23, 2007 10:05 pm ]
Post subject: 
nice looking car
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