gwhy!1
100 kW
Has anyone ever tried casting these pulleys in a metal loaded/ high temp resin ?... just looking at bobc pulley and and I think with the ali side walls this would be a very good solution and very cheap.
Belt drive Sprockets on the Cheap!
- Thread starter katou
- Start date
Kin
10 kW
bandaro said:
In general, I think you are right. Molding is often the way to go with trying to do any production with 3D printing tech. However, Injection molding is a little tricky and perhaps unnecessarily high volume. I was thinking maybe two part molds with release spray + hard urethane resin or anything else if anyone has good ideas for strong resins.
gwhy!1
100 kW
I dont think you would even need a 2 part molds to cast these pulleys, so it would be dead easy... I have used some metal loaded resin and copied some gears ( mod2 not for any think ebike related ) and they have help up very well, so something like one of the sections of bobc pulley would be a breeze to copy and due to the overall dia of the pulley there would be no chance of stripping teeth off the resin but im not totally sure how well it would wear.
JEB
100 W
Years ago as s tool & die maker at GM, we used Devcon plastic steel epoxy for some of our temporary forming dies, adheres well, has high concentration of metal.
Kin
10 kW
I'll keep these in mind. I'm imagining that multiple part mold might allow for a flange on the casting, but I guess a flange on a pulley really just delays problems. If it is resisting a tendency for the pulley to slip off (because of misalignment) then it's just adding frictional wear that will show up in the future.
bobc
10 kW
If anyone wants to run with this, I have a few design files that might be helpful - PM me if there's anything you want.
The original pulley has not yet been used because there are strong rumours of rule changes in the offing which would make development work potentially useless; I guess we'll have a better idea what's happening in a month or so.
Bob
The original pulley has not yet been used because there are strong rumours of rule changes in the offing which would make development work potentially useless; I guess we'll have a better idea what's happening in a month or so.
Bob
bobc
10 kW
Looking at systems for a new pedal bike - I didn't want to go back to chain drive & didn't want to pay a fortune for a "gates carbondrive" belt (last time I bought one it was £76). Anyway, I got a quote from a drives company for a goodyear 14mm pitch HTD cut to 10mm wide - £16+VAT. Tensile strength is 7000N, FOS would be about 3 i.e. good enough!
bobc
10 kW
We just used the CNC router to make some 80tooth HTD 5mm pulleys. What you see took just over an hour on the router, it's for 15mm wide belt.
I checked the HPC gears website - they want £55 for an 80t 15mm pulley. The picture below shows the pulley in 2 halves to clamp over a freewheel and be tried in the school racing car
So actually a cost effective route (rout)
Rule changes, as suspected, have made the big pulley described above redundant.
I checked the HPC gears website - they want £55 for an 80t 15mm pulley. The picture below shows the pulley in 2 halves to clamp over a freewheel and be tried in the school racing car
So actually a cost effective route (rout)
Rule changes, as suspected, have made the big pulley described above redundant.
bobc
10 kW
I should update about the drive pulley set I made for my pedal powered road bike a couple of years ago: basically the aluminium crank pulley failed after about 3000 miles & I replaced it with a stainless steel one. The "spokes" fatigued away - here's a stress picture (red is allegedly beyond yeild point!!)
here's the broken thing
here's the replacement in stainless
going fine - it's done a thousand miles or so. it weighs twice as much as the ally one (in spite of being much spindlier) but has a huge margin of safety strength wise.
Moral of the story - if you've go the tools to analyse stresses in a component - use 'em!
I was so lucky with this, I wasn't hurt, nothing else (not even the belt) sustained any damage, & from where it failed I was able to freewheel to my destination
here's the broken thing
here's the replacement in stainless
going fine - it's done a thousand miles or so. it weighs twice as much as the ally one (in spite of being much spindlier) but has a huge margin of safety strength wise.
Moral of the story - if you've go the tools to analyse stresses in a component - use 'em!
I was so lucky with this, I wasn't hurt, nothing else (not even the belt) sustained any damage, & from where it failed I was able to freewheel to my destination
bobc
10 kW
80 tooth 5mm pitch 15mm wide belt pulley, turning completed after routing 2 posts up
Hi all,
I was looking for a cheap big (>72T) htd or gt3 pulley so I'm very happy I found this thread!
With the front view of a gt2 5m belt from oem.cadregister.com and the outside diameter of http://www.sdp-si.com/D265/HTML/D265T016.html
I started to make my pulley design.
ONLY I am not sure about the way I made this drawing for a 90T pulley:
I extruded a diameter 142.1mm circle and cut out the profile of the teeth in the rectangle in the image below:
View attachment 2
I repeated this cutout 90 times with equal spacing. Which gave the result as displayed below
So question for the ones with more experience:
->Is this the correct way to model a pulley? Or should the profile be different somehow?
->How thin do you think I should make the individual plates when lasercutted in AL (to prevent deformation)? (I was guessing 5mm)
->Should I add a certain thickness of the laserbeam? Is this a value that I can ask the machining shop? (I have no experience at all with lasercutting)
Thanks in advance everybody!
I was looking for a cheap big (>72T) htd or gt3 pulley so I'm very happy I found this thread!
With the front view of a gt2 5m belt from oem.cadregister.com and the outside diameter of http://www.sdp-si.com/D265/HTML/D265T016.html
I started to make my pulley design.
ONLY I am not sure about the way I made this drawing for a 90T pulley:
I extruded a diameter 142.1mm circle and cut out the profile of the teeth in the rectangle in the image below:
View attachment 2
I repeated this cutout 90 times with equal spacing. Which gave the result as displayed below
So question for the ones with more experience:
->Is this the correct way to model a pulley? Or should the profile be different somehow?
->How thin do you think I should make the individual plates when lasercutted in AL (to prevent deformation)? (I was guessing 5mm)
->Should I add a certain thickness of the laserbeam? Is this a value that I can ask the machining shop? (I have no experience at all with lasercutting)
Thanks in advance everybody!
bobc
10 kW
Hi tuurb,
the only way I found to model the teeth was to buy the belt & measure it. The biggest surprise for me was that the tension members in the belt are a reasonable distance into it, so if you pick a base diameter that's the right diameter (N* pitch/pi) the belt teeth won't mesh right; I think you have to subtract about 0.5mm in diameter for an HTD5.
OK you seem to have done something like that already the tooth profile looks fine.
Aluminium isn't the best stuff for laser cutting, the result with, say, stainless steel, needs no cleaning up and it is possible to laser 5mm stainless - it may not be easy to get with ally.
Don't worry about kerf correction, they will do that with their own software.
I'd recommend stacks of 3mm thick, use stainless, make the design spindlier to lose some weight.
My bike pulley above used a mix of 2 and 3mm laminations to give me fine control of the beltline. I've no reason to suppose 5mm stainless wouldn't be equally accurate.
When I used aluminium on the original bike pulley, there was a LOT of work cleaning flash off the products before I could use em.
the only way I found to model the teeth was to buy the belt & measure it. The biggest surprise for me was that the tension members in the belt are a reasonable distance into it, so if you pick a base diameter that's the right diameter (N* pitch/pi) the belt teeth won't mesh right; I think you have to subtract about 0.5mm in diameter for an HTD5.
OK you seem to have done something like that already
the tooth profile looks fine.Aluminium isn't the best stuff for laser cutting, the result with, say, stainless steel, needs no cleaning up and it is possible to laser 5mm stainless - it may not be easy to get with ally.
Don't worry about kerf correction, they will do that with their own software.
I'd recommend stacks of 3mm thick, use stainless, make the design spindlier to lose some weight.
My bike pulley above used a mix of 2 and 3mm laminations to give me fine control of the beltline. I've no reason to suppose 5mm stainless wouldn't be equally accurate.
When I used aluminium on the original bike pulley, there was a LOT of work cleaning flash off the products before I could use em.
Thanks for the quick reply bobc!
I will be following your advice and started to design another pulley that I would make in Stainless steel which looks like this:
Because I want to save weight the second part is only fixed to the first pulley and not to the wheel it will be driving:
Then I saw that in my Solidworks version I could do simple stress analyses so I tried this.
BUT I'm not sure about any step of my calculations so feel free to verify everybody.
I calculated the force I will apply to the rear pulley:
I estimate that my motor hobbyking sk3 6354 213kv can deliver around 2kW. (2,55kW specs)
Full speed the sprocket will run at around 850rpm so 850*2*π 89rad/sec
(4V *213rpm/v * 5cells / reduction of 5 = 850rpm)
T=P/ω so 2kW/(89rad/sec)= 22,5Nm
F=T/r So 22,5Nm on a wheel with a radius of 100mm -> 22,5Nm/0,1m= 225N
With this force applied on an estimated count of 49 teeth Soliworks calculated a minimum factor of safety of 12 for stainless steel. (see attachement for an auto-generated report of the analysis)
I’m quite sure the force will be bigger when I’m accelerating from 0 but I do not know for sure how to calculate this…anybody?
I will be following your advice and started to design another pulley that I would make in Stainless steel which looks like this:
Because I want to save weight the second part is only fixed to the first pulley and not to the wheel it will be driving:
Then I saw that in my Solidworks version I could do simple stress analyses so I tried this.
BUT I'm not sure about any step of my calculations so feel free to verify everybody.
I calculated the force I will apply to the rear pulley:
I estimate that my motor hobbyking sk3 6354 213kv can deliver around 2kW. (2,55kW specs)
Full speed the sprocket will run at around 850rpm so 850*2*π 89rad/sec
(4V *213rpm/v * 5cells / reduction of 5 = 850rpm)
T=P/ω so 2kW/(89rad/sec)= 22,5Nm
F=T/r So 22,5Nm on a wheel with a radius of 100mm -> 22,5Nm/0,1m= 225N
With this force applied on an estimated count of 49 teeth Soliworks calculated a minimum factor of safety of 12 for stainless steel. (see attachement for an auto-generated report of the analysis)
I’m quite sure the force will be bigger when I’m accelerating from 0 but I do not know for sure how to calculate this…anybody?
bobc
10 kW
Hi tuurb
pulley looks nice, I'm sure you could shave off a bit of weight if you wanted but what's the point? Stresses on a pulley are about as benign & predictable as mechanical systems get; I would do another simulation though, you've done one sharing the load between half the teeth - now do one sharing between 6 to 8 teeth.
Your safety factor will come down a bit but a safety factor of 1.1 is good enough for this
Motor torque is proportional to motor amps & this should be controlled by the controller. It will (with a decent controller) be the same from 0 to base speed. The most significant intertia in the whole shebang is the driver, I wouldn't expect big transient torques to appear in the drivetrain.
PS the only other thing I might do is increase the number of small bolts holding the pulley laminations together - you have just 5 - I'd put 2 more between each taking it up to 15. Otherwise it's a very long span between supports on the side laminations. There's a larger section where the longer spokes meet the rim, you could put holes through there?
pulley looks nice, I'm sure you could shave off a bit of weight if you wanted but what's the point? Stresses on a pulley are about as benign & predictable as mechanical systems get; I would do another simulation though, you've done one sharing the load between half the teeth - now do one sharing between 6 to 8 teeth.
Your safety factor will come down a bit but a safety factor of 1.1 is good enough for this
Motor torque is proportional to motor amps & this should be controlled by the controller. It will (with a decent controller) be the same from 0 to base speed. The most significant intertia in the whole shebang is the driver, I wouldn't expect big transient torques to appear in the drivetrain.
PS the only other thing I might do is increase the number of small bolts holding the pulley laminations together - you have just 5 - I'd put 2 more between each taking it up to 15. Otherwise it's a very long span between supports on the side laminations. There's a larger section where the longer spokes meet the rim, you could put holes through there?
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