Looks a little smooth if you want to urithane the wheels?
There isn't much there to grab onto.
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Mechanical engineers build weapons, civil engineers build targets

I think the bottom of the Vee will need a little work in the mill to increase the surface area. Did I mention that UMHW is probably too soft to hold a key-way for long? I'm pretty sure it came up in a PM some time recently...
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

if it was a big keyway or you had more than 1 perhaps?
big = deep into the UHMW
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Mechanical engineers build weapons, civil engineers build targets

quote:

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Originally posted by Nick:
I think the bottom of the Vee will need a little work in the mill to increase the surface area. Did I mention that UMHW is probably too soft to hold a key-way for long? I'm pretty sure it came up in a PM some time recently...

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The hard facing rod idea was a great idea thank you and I was steering down that path until I hit another hurdle. The picture above is really what I want, and recent inquiries may suggest to me that its something I want to do. It would also solve two other problems @ the same time(and now I think about it maybe three). With a couple of phone calls and a quick drop in to the machine shop around the corner tomorrow, I will know for sure if its a goer.

Can anyone see any flaws in its design. 8mm aluminum wall, 20 X 12 teeth, the only bit I see as a bit 'on the edge' is that the teeth are only 3mm into the drum. But with a length of 350mm I believe its OK(yes that also means 5mm left for screw threads).
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Imagination is more important than knowledge. Knowledge is limited. Imagination encircles the world.
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I'd go with beefier screws into the aluminium and perhaps think about the end caps.
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Mechanical engineers build weapons, civil engineers build targets

Ends caps are sorted, beefier screws 8mm?
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Imagination is more important than knowledge. Knowledge is limited. Imagination encircles the world.
Albert Einstein.

I wonder if it would be worthwhile putting a strip of 12 mm * 3 mm steel along the inside of the teeth so that the screws can go into steel instead of aluminium.

I have no experience with spinners so take this as an uneducated guess.
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Get a strip of 10 x 10 x 350mm aluminium bar welded on the trailing side of the tooth, will give it a shelf to sit against.
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Something like this would work. Kind of what Aaron said.

Terribly bad idea to put the screws in that way . The impact forces will lever the tooth and backing bar off the drum, plus the screw heads are on the leading edge of the tooth and are more open to damage. The backing bar is an ok idea if the screws go into the drum as per Trent's original drawing.

I recall that some US guys (JR with Solaris, perhaps?) used a steel strip inside the drum to screw into, rather than the aluminium - it sounded like a good idea and increased the KE as well. How wide is that drum? if you can get your hands inside, You could just use a washer and nylock nut to save weight.

Personally, I would go with smaller screws, spaced closely together; if you use bigger screws, the scoss-section of the tooth at the screw holes is reduced and it is more likely to snap. How about running the screws from the inside?
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

I was just thinking of the tapped holes in the aluminium. M5 is about the smallest I'd go there. We have 8x M5's on each side holding the drum on Plan-G.
Make sure you end the bar with bolts too, don't leave them unsupported or they will snap off.
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Mechanical engineers build weapons, civil engineers build targets

I don't see it being a bad idea as that is how they bolt tub grinder teeth into tree mulchers.


The bolt will take no load and neither will the threads as there will be no force applied to them during the impact. In fact force on the screw will be reduced during impact. The screw heads are recessed and should take minimal damage. The ali backing is the only thing taking the load and since it won't be hit there will be no impact damage to the surface. If the backing is increased to more then 25mm thick it should not bend or shear.
Using a screw perpendicular to the direction of travel will always be a bad idea unless it is used as a lose retaining pin and I never seen that idea mentioned on any forum.

personally i like the anuerysm style drum teeth, you have two of say 15mm length each on either side of the drum on one side, than a single tooth 30mm long on the other, that way there is much less unsupported mass it gives almost a single tooth style effect.

gary also had a good idea on reboot, its just a normal tooth like you have but with some triangle bits welded behind it for big strenght.

i think the main problem is an 8mm aluminium drum. i can see that imploding more or less on the first hit. reboot and viscerals drums both have some pretty nasty dents in them and theyre both at least 5-6mm steel. i would think something of even more diameter made out of that would be pretty gone in a few matches
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Wow good work guys thanks for the ideas, I wish I had kept to my promise and made those inquires today but I was too busy @ work.

Does anyone else support Glen theory of the thickness of the drum @ 8mm? That scares me a bit.
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Imagination is more important than knowledge. Knowledge is limited. Imagination encircles the world.
Albert Einstein.