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We can keep a karts rolling resistance to a minimum by making sure all bearings are working properly. We can do this by making sure the front hub bearings are kept lubricated and by making sure the rear axle bearings are seated correctly so there is no unwanted load acting upon them.
Once we have done all we can to minimise friction caused by the chassis itself, it's time to drive some power through it. We want to transfer as much of the precious (and sometimes very expensive) horsepower to the rear tyres as we can. There are only three components that we can control, these are;[*]Engine sprocket[*]Chain[*]Rear SprocketToday we are looking at Talon rear sprockets which are marketed as a premium sprocket for optimal performance and reliability.
I have been using Talon sprockets on and off for a few years now. If I’m visiting a circuit at which I am not sure of the correct gearing, I will buy a sprocket of the size recommended by the club, one sprocket a tooth larger and one sprocket with one less tooth than the recommended. This gives me a few options straight out of the box, just in case the circuit shop is closed on the Saturday or they have sold out. It also saves me running backwards and forwards using up precious spanner time.
Price for three Talon Sprockets £38.34
Price for three Spellfame Sprockets £27.00
Now, for the super scrimpers out there you may be thinking “It's only a sprocket, I will save myself a tenner and get the cheaper sprockets.” And there’s nothing wrong with that, especially if you want to use the cheap sprockets to find your ideal gearing and then possibly drop a few extra quid on a higher quality sprocket.
Personally, I like to build a collection of new sprockets. If you trash a sprocket in the first heat for some reason and then can't get hold of another high quality sprocket, you may spend the day running around on a sprocket that wears out faster than Homer Simpson on a treadmill.
Now, on to the sprockets! When you get your hands on the sprocket you instantly know you have paid more of your hard earned cash for it. It has a laser etched logo with the model number and amount of teeth above it. It's very well finished throughout with no burrs or blemishes on it's surface.
Throughout the rest of this review I will be comparing the Talon Sprocket to a cheaper, but still described as a high quality sprocket available from Spellfame UK.
Note: In this review we used a smaller 74T Talon sprocket as opposed to an 85T Spellfame sprocket.
The Talon sprocket is made of 7075 Aircraft Grade Aluminium, which I can confirm is in fact “Aircraft Grade” as I often use it when manufacturing components for the Tornado GR4.
It's hard to find information on what grade of material is used in the Spellfame sprocket but from looking at it I can tell that it is certainly a grade which is rolled to a much larger tollerance than the Talon sprocket. The surface finish is much less consistent and when laid on a granite bed it rocked considerably more than the Talon sprocket which felt rock solid. This warping issue is probably caused by one of the machining/work holding processes used rather than the flatness of the material from the manufacturer.
I would also be confident that the sprocket is not as hard as the 7075 aluminium used in the Talon sprockets as there are a few tell tale signs of burrs being thrown up in the machining process and then quickly ground back with sandpaper or similar abrasives (Softer materials tend to be harder to machine and achieve a good cut/surface finish than harder ones, within reason).
The Talon sprocket manages to be burr free, without any “finishing off” or “de burring” by hand. This could either be better use of the machining processes, better quality tooling (less worn) or from the increased hardness of the material. It's more likely that all three of these things contribute to a much higher quality end product.
On this subject I would like to mention that on some cheap sprockets I have found surprisingly large burrs in the sockets where the chain barrels seat. More on that later.
The following images are direct comparisons between the Spellfame High Quality Sprocket and the Talon Sprocket.
The sprockets in all their glory
In the above shot, you can see that the lightening hole arrangement is different than on the Spellfame sprocket. The Spellfame sprocket goes for an equally spaced PCD (Pitch Circle Diameter) whereas the Talon has the holes in pairs along it's PCD. Initially I thought this may have been due to the size of the sprocket not leaving enough room for the drilled holes to mount the sprocket onto the carrier. I found that even on an 84T Talon sprocket, it still had the same arrangement.
Also worth noting is that the lightening holes on the Spellfame sprocket appear to stay the same size no matter what size the sprocket is. For example, a 75T and an 85T both have equal size lightening holes. This means that on larger sprockets the holes look rather small and are not saving as much weight as they could.
The Talon, on the other hand have different size lightening holes for each individual sprocket size. They increase in diameter with the size of the sprocket, therefore keeping the ratio more equal. This means that the larger sprockets save more weight than on the Spellfame sprocket.
The Talon has a slightly different profile at the top of each tooth
Talon has laser etched branding opposed to the stamped number of the Spellfame sprocket
Close up of the inside profile
You can hopefully get an idea of the difference in surface finish in this shot.
In the following images you can clearly see that the lightening holes in the Spellfame sprocket have been punched out, whereas the Talon holes have been machined. This could also be a contributing factor to the overall flatness of the sprocket.
Earlier on in the review I mentioned some burrs on the cheaper sprocket. In this image I have highlighted the issue. Now, these are not too bad but I have seen the odd sprocket with much worse burrs than this. The problem being these burrs break off during use and when combined with chain lube act as a metallic grinding paste. We are trying our hardest to keep our chain clean to prolong the life and maintain its efficiency, the last thing we want to do is introduce these metallic fillings before the kart even hits the track.
Late last year I was able to run the dream team of components for what should be the most durable set-up available. I ran a Talon sprocket, a brand new Rotax engine sprocket and the HAT Panther chain. I also ran a brand new OTK sprocket carrier to make sure I had everything as it should be.
I ran all of Saturday, flushing out the chain with brake cleaner and then drying with blue roll between each run. I inspected the sprocket and chain wear and could not believe how well it was holding up. Usually I would consider replacing the sprocket for Sunday but I saw absolutely no point as there was minimal wear to the edges of the sprocket and the profile had shown no wear whatsoever!
Unfortunately, before I was able to test a cheap sprocket with the set-up, my sprocket carrier shifted when hitting a curb particularly hard and snapped the chain. I would have been interested to see how a cheap sprocket held up compared to the Talon when paired with a HAT Panther chain.
Never the less, I have since used a Talon sprocket with a standard Gold chain and found them to simply outlast the cheaper sprockets available. They still wear if you don't have all of the alignment correct and fail to clean it, but they definitely appear to cope with wear better than the cheaper sprockets when everything is as it should be.
So, on the durability front, the Talon definitely do a better job than the cheaper sprockets. They are of a much higher quality throughout and this can stop unwanted metallic fillings being introduced, which can increase wear rates. We would be interested to see if there was any difference in performance by use of a dyno, and to see if the positioning of the holes make any difference to the balance of the sprocket.
If you are extra careful with your kit, and keep the drive train clean after each run, you can make any sprocket last a long time. But sometimes having a sprocket that is able to resist wear that little bit better, could mean the difference between crossing the line and pulling off to the side as your engine screams at the loss of it's beloved chain.
There are sprockets available that are much worse than the Spellfame sprocket we compared the Talon against today, and we may re-visit this subject to compare the two opposite ends of the spectrum. With this in mind we are going to give a brief scoring of the Spellfame sprocket too.
- Resonable quality
- If maintained properly, has good durability.
- Poor machining quality
- Less durable material
- Lightening holes a fixed size
Spellfame Kart Review Score 14 out of 20
- Excellent quality
- Lighter larger sprockets
- Higher grade material
- Very durable
Kart Review Score: 8.5