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.5 pounds, 5 inch wheel, machined from a solid block of aluminum. Please leave feedback
Discussion
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17-08-2008 19:28
chris31
Re: pic: 5 Inch Wheel
The first thing I see missing is no key or bolt pattern for a sprocket.
17-08-2008 19:42
RMS11
Re: pic: 5 Inch Wheel
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Originally Posted by chris31
The first thing I see missing is no key or bolt pattern for a sprocket.
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17-08-2008 19:49
gblake
Re: pic: 5 Inch Wheel
The spokes look nice; but I'm curious if there is any mathematical basis (or any other basis other than artistry) for their shape?
FYI - I have no hidden agenda or Socratic teaching attempt hidden in my question - I am certainly not good enough at mechanical engineering to perform anything other than the grossest levels of analysis to answer a question like the one I just posed.
Instead, each time I see a design like this one posted as a CAD rendering, I am sincerely curious what design guidelines, or computational analysis, or empirical data the author was able to use when creating the design. Yours just happens to be the one that finally got me to ask the question.
What can you tell us?
Blake
17-08-2008 20:17
RMS11
Re: pic: 5 Inch Wheel
I first cut out 5 spokes that went fully from the center to the outside with all inside material cut out. I made them 1/4 inch because I felt that to be plenty to support the wheel. I filletted the edges of the spokes for extra support and thev used cosmosxpress in solidworks to run stress analysis, placing an 120 lb force on an individual wheel supported by the axle. Then after seeing it would not break I cut more weight by adding holes in an artsy way and did more stress analysis. Really I find the best way to make light weight objects is to cut a little weight and then stress test and repete until you are either happy with the weight or unhappy with how strong it is getting.
17-08-2008 20:35
Triple B
Re: pic: 5 Inch Wheel
personally i would favor a broached hex to the keyway for strength
mike d
17-08-2008 20:37
AdamHeard
Re: pic: 5 Inch Wheel
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Originally Posted by RMS11
I first cut out 5 spokes that went fully from the center to the outside with all inside material cut out. I made them 1/4 inch because I felt that to be plenty to support the wheel. I filletted the edges of the spokes for extra support and thev used cosmosxpress in solidworks to run stress analysis, placing an 120 lb force on an individual wheel supported by the axle. Then after seeing it would not break I cut more weight by adding holes in an artsy way and did more stress analysis. Really I find the best way to make light weight objects is to cut a little weight and then stress test and repete until you are either happy with the weight or unhappy with how strong it is getting.
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But, overall, a solid start on a wheel design.
17-08-2008 21:00
R.C.
Re: pic: 5 Inch Wheel
The torque is mainly at the shaft or the middle of the wheel. As you move farther from the center, the torque decreases.
17-08-2008 21:02
AdamHeard
Re: pic: 5 Inch Wheel
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Originally Posted by RMS11
Why does torque decrease as you get farther away?
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And for what Mike says, YES!!!! If you can find a way to use hex axles, do it. They form a stronger connection than a keyed shaft, and are just way easier to work with... On top of that you never have to worry about losing a key, or making them in the first place.
17-08-2008 21:07
RMS11
Re: pic: 5 Inch Wheel
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Originally Posted by AdamHeard
The torque doesn't change at all, but if you pick a cross section of the spoke, you can say the force on it (from the torque) is the torque divided by how far it is from the center. Think of it as a lever arm, if you apply a torque to the end of it, the force the end of the lever exerts decreases as the lever's length is increased.
And for what Mike says, YES!!!! If you can find a way to use hex axles, do it. They form a stronger connection than a keyed shaft, and are just way easier to work with... On top of that you never have to worry about losing a key, or making them in the first place. |
We might go with hex. Is it hard to find hex sprockets and what do you use as bearings with a hex shaft?
17-08-2008 21:13
Triple B
Re: pic: 5 Inch Wheel
pink uses flanged bearings and hex stock from mcmaster carr.
you can put the hex stock in a lathe and turn it under size so the bearing slips on and the remaining hex locates it from side to side
mike d
17-08-2008 21:14
Richard McClellan
Re: pic: 5 Inch Wheel
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Originally Posted by RMS11
Why does torque decrease as you get farther away?
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Torque = Force x Distance, so as distance increases, force decreases.
Edit: Beat to it.
17-08-2008 21:15
chris31
Re: pic: 5 Inch Wheel
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Originally Posted by RMS11
Thanks
We might go with hex. Is it hard to find hex sprockets and what do you use as bearings with a hex shaft? |
EDIT: Mike beat me.
17-08-2008 21:18
RMS11
Re: pic: 5 Inch Wheel
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Originally Posted by chris31
Take the hex shaft to a lathe and turn it down to a circle that will fit into a bearing.
EDIT: Mike beat me. |
Ya thats our problem, we have a mill but no lathe. We could do it, but it is a huge hassle and we wouldnt have the freedom of doing this in shop... Hopefully we will get one sometime...
17-08-2008 21:21
R.C.
Re: pic: 5 Inch Wheel
1323 would machine it out for you if you guys needed, just email me. We machine out parts for teams in need.
17-08-2008 21:25
Triple B
Re: pic: 5 Inch Wheel
unless you would have to chew the shafts with your teeth, it will be worth it compared to keyways, also its a very basic machining practice with a reletivly loose tolerance if you needed to pay someone to machine them for you.
mike d
17-08-2008 21:25
RMS11
Re: pic: 5 Inch Wheel
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Originally Posted by rc_cola1323
1323 would machine it out for you if you guys needed, just email me. We machine out parts for teams in need.
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17-08-2008 21:26
R.C.
Re: pic: 5 Inch Wheel
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Originally Posted by RMS11
Thanks, are you in atlanta?
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17-08-2008 21:30
Triple B
Re: pic: 5 Inch Wheel
i would think there would be plenty of shops around atlanta that would be able to do it, if not, I am in florida, send me some dimensions and i will whip them out for you.
mike d
17-08-2008 22:21
=Martin=Taylor=
Re: pic: 5 Inch Wheel
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Originally Posted by RMS11
Ya thats our problem, we have a mill but no lathe. We could do it, but it is a huge hassle and we wouldnt have the freedom of doing this in shop... Hopefully we will get one sometime...
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We did this with our mill and a dividing head. We never bought any broaches or hex shafts. Just used the parts from AM and metal bars laying around my barn.
It depends on the design.
18-08-2008 02:27
Qbranch
Re: pic: 5 Inch Wheel
While it's true you can't really make a very good keyway on a mill, you may be able to make a hex or D-shaft bore on the mill. 1/8" end mills are available up to about 3/4" in length, so you should be able to mill a hex shaft bore out of the block.
And, now you're all about to type 'what about the rounds on the corners from the round cutter?'. Well, personally, whenever things really need to be square I do one of two things: 1, before the milling operation, drill holes at all of the points the fillet would be left from the end mill, thus removing this excess material. Or 2, If you want to be trickier and more efficient, program over-travels the length of your tool's radius away from the center of the bore you're making, also eliminating the corner radius. With a hex shaft, you should still have plenty of surface area left on all of the sides of the shaft... you should only lose 1/8" of each side.
If you're mass producing these, you can always cut your bore times by starting with a larger tool and only finishing the corners with the 1/8" tool.
-q
18-08-2008 03:36
=Martin=Taylor=
Re: pic: 5 Inch Wheel
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Originally Posted by Qbranch
While it's true you can't really make a very good keyway on a mill, you may be able to make a hex or D-shaft bore on the mill. 1/8" end mills are available up to about 3/4" in length, so you should be able to mill a hex shaft bore out of the block.
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18-08-2008 23:55
NickE
Re: pic: 5 Inch Wheel
A much easier solution than milling out a hex is to broach it. Mcmaster sells hex and square broaches in a variety of sizes.
http://www.mcmaster.com/#catalog/114/2462
At $128 for a 3/8" hex broach, they're not cheap. However, they will certainly save time over milling out a hex. Also, your hex come out without rounded corners.
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