Scooterotica

The first prototype Gran Turismo crank shafts are being assembled for testing. It has taken over 18 months to optimise the design of the webs and stuffers to produce this full circle, balanced crank (optimum balance on 58/110 with 350LC piston). During this time specific software has been used to calculate balance masses, CoG's and mass off sets. To cross check information, OEM and existing cranks have been modelled and balance information compared.

The initial 10pcs prototype specification will be 110 rod, 58 stroke based on CNC machined Indian GP webs.

Production will be based around 58 and 60 stroke GP webs (Indian and Italian) with three rods (110, 115 and 125) and two pins 22mm dia and a 22/24 off-set pin which offers 6 variants of crank configuration all 40.5mm wide.

Why is this crank project different?
The crank is production orientated, specific fixtures for machining and assembly have been made, for production stuffers will be injection moulded. This is all done to optimise cost and return value for money.
It's fully CAD designed to achieve precision balance and assembly
It's a genuine full circle, low drag design
It's the lightest crank available (lighter than OEM)
How long? Well, there is still some way to go in testing first, I'd say about 4-5 months before production if all goes well.
How much? Well, depending on the response from dealers the specification will come in three levels, the targets are: 1. lowest cost £130 (donor Indian GP webs), Mid £170(new Indian Webs), Top £220(new Italian webs). The use of 125mm rods and off-set pins will be slightly more.

Fantastic product from what I've read and heard so far, looking forward to seeing these in production. Cheers Rich.

Tremendous ,Well done Rich T

About time too!

I've been waiting for a decent HPC crank to become available (60mm version for me... but uprated 107 rod and bearing wanted). Taffspeed and Readspeed both did bolt in packers for a while but now everyone seems to do full circle webs with pressed in weights... many of which seem to come loose and cause issue at high mileage

By the look of it, this could be a decent option, provided you are going to offer a standard 107 upgraded rod too (?). I'm not interested in 110 rods for some engine configurations, regardless of what others may say about rod length ideally being 2 x stroke or 2 x bore... I'd just like to get my hands on a decent HPC 60mm stroke crank with decent bearing, a well shimmed big end and standard 107 rod, which can drop into most motors without starting to look at packers.

^... that said, looks like a darned fine crank

Adam

Adam

Fantastic crank Rich. What's the weight reduction over a standard crank?

dapper wrote:Fantastic crank Rich. What's the weight reduction over a standard crank?

Because the Indian forgings vary a little, it depends on the Indian crank you have. Typically, the variance I see is that the new crank is around 170gms lighter than stock but has a significantly larger mass offset -8.3mm compared to the OEM crank which is 6.3mm.

I buy rods in MOQ's of 50pcs but this supplier does not have 107 rods and I don't want to split up the purchasing. Adam, as you are particularly in love with a 107 rod I'd suggest you source one, bring it over and we'll fit it together (I have loads SIL 107 rods in a bucket but I guess you wouldn't want one of those).

The prototypes also do not run shims and are machined for clearance on 16mm. This means the max combined width of rod and shims is 16mm. Depending on how the prototypes perform, we'll make a decision on shims or no shims. The balance to strike being the sacrifice of pin press fit v big end bearing area and if shims bring anything to the party. I know people have their opinions on shims but I want to be entirely objective during the testing.

^... good considered response.

I guess that I could look at the cost of an uprated rod and bearing kit from AF as I've had very good service from their uprated cranks over the years. However, I don't need a crank this minute so I'll hang fire until you've done some testing, see how you get on and then see where I'm at.

Cheers... watching with interest

Adam

Adam_Winstone wrote:^... good considered response.

I guess that I could look at the cost of an uprated rod and bearing kit from AF as I've had very good service from their uprated cranks over the years. However, I don't need a crank this minute so I'll hang fire until you've done some testing, see how you get on and then see where I'm at.

Cheers... watching with interest

Adam

Yes, sounds like a plan. I'm going to the show in Germany this year so might come across something there, I've got a couple of meetings set up.

125mm Rod.

What application do you have in mind for a 125mm rod?

SF

Spanish Fly wrote:125mm Rod.

What application do you have in mind for a 125mm rod?

SF

It is a project we call "The Blair Witch". It is a 275cc LC case inducted barrel, it is 60 stroke and 76mm bore with a JS650 piston We've cast 3 to date and building the second engine. The crank config will be 58 stroke with the 22/24 eccentric pin to make 60 stroke but with as much meat around the pin as possible. The first engine was 58 stroke 76 bore and gave about 35bhp as I remember. You really need a bigger rod for that type of top end.