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BritNerf Flywheels

I've been sitting on the idea of a BritNerf flywheel for about two years now. Since I've recemtly upgraded my lathe, I think now is a good time to have a stab at it.

There are a few replacement flywheels on the market these days, but none of them have published any development information and that concerns me a little. BritNerf has a reputation for good data so I'm going to apply our famous diligence to these. If the results show that Worker/Artifact/Blasterparts wheels are the best then so be it, we will have proven that they are the best design and that is fine by me. If not, then we could develop our own.

To start off with, I would like to experiment with three variables: dart crush, concaveness and surface texture. Mass was another consideration but since that will only affect flywheel 'sag' we can mess about with that once the ideal design is nailed down.

Since we can't experiment with concaveness and surface texture until we have a prototype, the first variable I will tackle is dart crush.

I have built a solid test rig which will enable us to precisely alter the flywheel gap so we can see what's what. Whilst thinking about what flywheels to use on the test rig my initial thoughts were to go for Worker wheels since there's already tons of data on them so it'd be easier to see differences in the results.

I'll have pictures of this rig soon. Until then I want to hear your thoughts. Are there any other variables worth testing?

I think you've covered most bases. Diameter and profile are probably the two major variables (a good concave profile would likely also increase the crush force, and therefore friction, as it should prevent the dart from simply flattening out). Surface finish shouldn't be too critical other than possibly for foam buildup (smooth glossy surface is likely better but worth testing) or if you want to experiment with "treads" to try and shed water from wet foam (although it might not be worthwhile).

The amount of crush you settle on will likely be a compromise. A low level of crush will result in poor performance whereas a very high level of crush would rule out lower torque motors and be a bit hard on motor bushings/bearings. Obviously eventually you'd also get to a point where the darts simply can't take any more or at least wear far too quickly to be practical - as long as the wear doesn't affect flight that may not be an issue (although I guess that depends on how many times people expect to re-use darts).

I personally wouldn't worry about mass too much. More mass (at least nearer the outer diameter - additional mass in the centre does very little to the moment of inertia) does mean less drop in flywheel speed but also longer rev and recovery times - if the motors aren't powerful enough in the first place you'll still see a steady drop in velocities at high RoF and if the motors were powerful enough to maintain a decent speed under load then the extra mass isn't doing anything. You've effectively filled a sink through a tap - if the water (energy) coming into the sink (flywheel) from the tap (motor) can keep up with the water leaving the sink through the drain (dart) so that the water level in the sink (flywheel speed) remains constant then the size of the sink in between doesn't really matter, it'll just take longer to fill in the first place if it is larger. If the tap can't keep the water level steady then that water level is going down whatever you do. It gets a little more complicated than that, since the flow through the tap effectively increases as the water level drops (the guy panics and opens the tap a bit more), but it does largely hold. Moral of the story - buy a better tap motor.

EDIT: Apparently I spew up weird water-based analogies when I try to think this late at night. Razz

I think the best thing to do will be to take the Blasterparts flywheels and make them 1mm larger in diameter. They're incredible pieces of engineering; they just fucked up the dimensions leading to sod all muzzle velocity. Smile

Oh and obviously willing distributor over here...

The main complication I foresee is the issue of different dart types yielding widely varied results. For instance, a Koosh dart has rubber right up to the edge of the foam whereas an elite doesn't really have any rubber that should be contacting the flywheels. And I have a feeling those new accustrike darts will muck things up as well. Regardless, I don't mean to discourage you from the experiment, as I am very interested in the results!

I would be interested in getting involved in this type work. I have CAD, CAM, CNC, and time at my disposal.

Are you only looking at fly wheels that would fit in stock cages?

Would it be worth gathering the dimensions of all the existing flywheels?
I have a nice cad model that will 'spring' to given dimensions. (soon to have a nice CAM tool path which will do the same)

The main complication I foresee is the issue of different dart types yielding widely varied results.

- this is demonstrated quit well in 498 Nerf's video of the artifact cage and wheels

My thoughts would be to optimise for koosh(not that i own any)

All that is to do with crush. FVJ can't tolerate as much crush because of their awful tip compound.
All your skills would be very welcome, there is a guide model on the forum already somewhere.
A high and medium crush version would be good. Right now i would like a similar crush to worker only as smooth and well machined as blasterparts.

Dan_jackson1985 wrote:
I would be interested in getting involved in this type work.

Excellent. The more the merrier. I'll be in touch once we get to the prototyping stage. I should imagine your lathe is more manly than mine so your precision should be better.

At this stage were just looking to see what dart crush does to performance. I should imagine we'll end up with two different flywheels. One optimised for Koosh and one for stock darts. The data will be interesting.

OldNoob wrote:
Right now i would like a similar crush to worker only as smooth and well machined as blasterparts.

any idea on dimensions of these?

I can send you a Worker wheel if required. I have an odd number due to replacing someone's bent one out my stock.

OldNoob wrote:
I can send you a Worker wheel if required. I have an odd number due to replacing someone's bent one out my stock.

That would be great! - will pm my address

Obviously I'm willing to do any required user testing....

Cool, the only testing i can do is based on how loud the Mrs shouts and what she calls me!

It's fine, there are plenty of us with chronographs and other testing equipment. Razz

I have the girlfriends bum for the my own version of the chrono....

If this is the consensus I guess we can bypass the scientific approach and come at it from an engineering standpoint.

Make several different flywheels copying the BP design, but with various different diameters. Increment by 0.5mm or so and then we can test them in stock cages with various different darts.

Sounds good.
daniel k

my DT teacher has a younger son really in to his blasters, and has previousley expressed interest, so i could try getting him on board.

I'll order a crate of Koosh and warm up the chrono... Happy to pay in full for each pair you send me. Smile

Very interested in this, especially regarding dart compatibility and accuracy more then FPS to be honest.

Today would there be a particular flywheel you would recommend because I keep reading mixed messages over those available, hard data would be great! Even better if you guys use this to develop a new 'perfect' flywheel pair.

Flywheels will have the main impact on dart compatibility noise and spin up time as well as FPS.

I suspect however that accuracy would be much more affected by the cage design such as stiffness and canter (ie offset tilt). The aluminium ones are not cheap so if you were to consider looking at a cage matched to a motor size and flywheel set that would be very nice.

That is till accustrike darts take over the world with all their newfangled heavy spinning dart ways? Wink

Accuracy is entirely a function of precision in your build and what darts you shoot. If you want better accuracy take more care over component selection and installation then use heavier tip darts like FVJ. The Britnerf wheels will be aimed at providing consistently high velocities with the best production tolerances possible, combined with dynamic balance for noise minimisation to enable more simple wheel selection. See Franksies post on flywheel matching to see the current process required to just get a pair of wheels that are within tolerance.

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