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Aluminium Specs


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vibrac

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I am making a sprocket carrier for our twin racer I am making it out of 6082T6 this seems suitable and available in the large size i need commensurate with cost
I am thinking perhaps I should harden it after machining, as I have had some wear in bolt holes on previous items (OK they may have come loose :eek:)
comments welcome
 

Comet Rider

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I'll dig out my dad's "Fletchers" book later
It lists all Aircraft alloy spec's as well as treatment methods
 

litnman

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This sprocket carrier was made for a drag bike from 6061T6 in 1957. It's still in good shape. I don't find much difference between 6061T6 and 6082T6.
Sprocket carrier.JPG
 

greg brillus

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As tempting it might seem to machine lightning ribs or spokes in the carrier, i recommend you don't. The power pulses from the engine will cause cracks to appear, especially if running a belt primary that offers no shock absorbing from these pulses. I found this within a years use on the racer.........
 

davidd

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Crack 02.PNG
This is Greg's sprocket a year or so after it was put into use. Greg change the design to one without spokes, which was very similar to the design I was using.
100_0035.jpg
Mine, which is above, is 6061, but it has never cracked. Bob Lamour made a batch of these based on my drawing. It replaces the drum, but it is for a 1/4" chain. This design takes the Suzuki RM sprocket, which is an off the shelf item. I use a 7075 sprocket from Sprocket Specialtist. It was a real help getting rid of the Vincent sprocket.

David
 

vibrac

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Great minds think alike David :cool: except I am going to use Honda 450 sprockets with the small belt you need 45 teeth or less sprockets on 520 (1/4) chain
I think we are going to use. Composite steel/alloy sprockets they are cheap enough
 

greg brillus

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With the 1000 cc engine I found that with the 1.66:1 Bob Newby primary ratio and a 21 tooth front sprocket, the rear I ran a 44 tooth sprocket on pretty much all the tracks. I originally ran a 41 tooth, but this seemed to bog the bike down too much, and the drive out of corners was poor. I use to shift at around 5800 and max rev's down long straights would hit 6200 but only for a second or so. These were at Philip Island and Eastern Creek in Sydney..........
 
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vibrac

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The spares company have a 22 teeth 1/4" gearbox sprocket which will just pass through the G50 plate. One of the first meetings hopefully we will do in 2020 will be Silverstone. I was a young guy the last time I rode a Vincent there so we shall need a good range of sprockets to chose from. luckily scramble guys ( sorry MX) get through a lot of rear sprockets so they are cheap to buy.
The other thing I have never resolved is the 10 hole 5 hole hub quandary they must have had good reason back then to have two types but I can't believe that 5 well fitting cap screws nowadays is not enough or that 10 loose standard hex bolts is insufficent
 
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greg brillus

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Tim are you and Ben running a 4 or 5 speed box.......I found with the 5 speed I never needed to change sprockets, the bike had enough torque and flexibility to cope with small and larger tracks. I know on the smaller capacity singles and the like that you have to change them more to suit the tracks.
 

Pushrod Twin

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I am making a sprocket carrier for our twin racer I am making it out of 6082T6 this seems suitable and available in the large size i need commensurate with cost
I am thinking perhaps I should harden it after machining, as I have had some wear in bolt holes on previous items (OK they may have come loose :eek:)
comments welcome
To late to harden it, if it comes as T6 the job is done. T6 is by definition solution heat treated & artificially age hardened which means it was heated in an oven or salt bath to its upper critical temperature, from memory about 525Deg C, then quenched in room temperature water. The hardening is followed by reheating in an oven to 120-170C then air cooling.
If you are concerned about wear in bolt holes then I would suggest fitting interference fit shouldered steel sleeves to spread the load. Use the 10 bolt hole hub, no question. I know it's a racer & you want to add lightness, try the 5 bolt hub, no steel sleeves first, when it cracks or comes loose on the bolts, you have next season's solution. :)
 

vibrac

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Tim are you and Ben running a 4 or 5 speed box.......I found with the 5 speed I never needed to change sprockets, the bike had enough torque and flexibility to cope with small and larger tracks. I know on the smaller capacity singles and the like that you have to change them more to suit the tracks.
No 5 speed I am afraid the pockets are empty I would like another set as they seem to be a operational improvement apart from the gear range advantage but we will have to see later
 

oexing

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Aluminium 6061 is not common in my country but you get lots of 7075 any day. But in places like the sprocket bolts at the rear I´d most likely put a good amount of low strength Loctite on the threads and shanks of the bolts. This produces some sort of plastic bushes in there and should transmit all forces evenly in all joints consisting of threads and parallel fits. It is not easy to fabricate perfect fits on serial production parts like drilled sprockets and hubs. So Loctite is a good way to spread loads in all components like here. Low strength is good enough, higher viscosity could be good depending on how big the gaps may come in drilled and tapped parts. Still in the design phase I am trying to dream up a design with axial splines like the Hirth spline , perfect for torque and positioning duties. When seeing cracks in sprocket adapters this is a telltale of too high loads due to uneven load spreading or overly stressed crosssection at these places. Aluminium does not forget high stresses and this reduces useful life in components - unlike steel components. Anybody who got alu conrods in his engines will know to change them in intervals when used in racing engines - or high mileage engines like Norton or Triumph twins or so.

Vic

P1050361.JPG
 

bmetcalf

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Is the depth of those splines tapered? If so, as a non-machinist, that seems quite a challenge to make the mating component fit with full contact. I suppose CNC machines would go a long ways for that. How the Hirth crankshafts are made to have the throws in phase has always mystified me.
 

oexing

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Hi Bruce,
yes, the splines are a bit of a challenge, there are variations: You aim for parallel tops on the splines. As the grooves are radial this requires grooves at an angle. Plus same goes for the corresponding spline so at that part you have different angles to match. There are ways to calculate all sizes but then I am no good in maths. So instead I do as I believe and later I try to get a measurement of the result and figure out what angle I need for the matching spline. But anyway this type is a fascinating bit of engineering. The spline in the photo is a propeller adapter machined on my round table - and the second try : The first would not fit as I had just one single groove too short , made a mistake in counting numbers of grooves. You would not believe just one groove wrong in total numbers and the lot is useless - and CNC would not help . . . . .

Vic
P1050179.JPG
 

vibrac

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Oexing was in line to what I was thinking with my 5 bolts so its just a case of using the correct loctite.
I think bearing in mind the thin wall between the 5/16 bolt hole and the central hole this would be the best solution
Obviously this loctute application would have to be done at the final tightning stage or the bolt could move after setting under tightening torque especially.
 

oexing

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In case you are worried about motion in the bolt assembly after applying Loctite, this is not critical. The glue will still be in there and any required locking effect in the threads is not compromised by some twisting at the bolt. Just try some Loctite on a bolt with its nut, you will need all the force for several turns to undo the nut finally. This is quite different to any other locking devices like split washers or so. But of course you don´t pick high strength Loctite types, low or normal is OK, else you will need a torch to undo later.

Vic
 

Cyborg

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There are ways to calculate all sizes but then I am no good in maths. So instead I do as I believe and later I try to get a measurement of the result and figure out what angle I need for the matching spline. But anyway this type is a fascinating bit of engineering. The spline in the photo is a propeller adapter machined on my round table - and the second try : The first would not fit as I had just one single groove too short , made a mistake in counting numbers of grooves. You would not believe just one groove wrong in total numbers and the lot is useless - and CNC would not help . . . . .
Vic
Nice work! I suspect that if I tried to cut something like that I would end up under my bed curled up in the fetal position sucking my thumb and crapping my pants. I made my first gear about a year ago. Reading the Machinerys Handbook just about caused my head to explode. Thank goodness for YouTube.
What a thrill when the last tooth turned out the same as the others. I was told that thrill never really goes away no matter how many gears you cut.

On a side note, I find it interesting how strong even the low strength blue Loctite is when the fasteners are absolutely clean. I also find it interesting that my bride complains bitterly about the acetone stink, but she has no problem using nail polish remover??
 
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