Where to find drive system parts online [List on Top]?
- Thread starter swbluto
- Start date
liveforphysics
100 TW
Enlarging a hole to a much larger size, say 4x the previous size, is a very easy task. Making a precision slight increase in hole size is often tough.
A bit holds it's center because the taper on the leading cutting edge forms a cone in front of it while the hole is being drilled, and this cone causes pressure to force center the bit, and keep it cutting straight (in uniform density materials at least).
When you enlarge a hole only a slight bit, you have no cone to center the path of the bit, and the bit tends to flex over and grab and bite into the material. For some materials, it's hardly a problem. For other materials, it's an awful PITA. Nylon is one of the materials that is generally a PITA.
Tap magic is cutting oil. Should not be used with plastic.
A bit holds it's center because the taper on the leading cutting edge forms a cone in front of it while the hole is being drilled, and this cone causes pressure to force center the bit, and keep it cutting straight (in uniform density materials at least).
When you enlarge a hole only a slight bit, you have no cone to center the path of the bit, and the bit tends to flex over and grab and bite into the material. For some materials, it's hardly a problem. For other materials, it's an awful PITA. Nylon is one of the materials that is generally a PITA.
Tap magic is cutting oil. Should not be used with plastic.
Would filling the bore with some kind of material aid in the bit guiding task? Like maybe some kind of epoxy? It seems like the pulley will be made of aluminum. So maybe, aluminum shaving filled epoxy to approximate uniform density? Or maybe insert a 1/4" inch rod (Aluminum - assuming I can find that somewhere) cut to size and glue it in?
And then the center would be center punched to get it center and everything.
Would that be more desirable for 'results' if a n00b was attempting this?
And then the center would be center punched to get it center and everything.
Would that be more desirable for 'results' if a n00b was attempting this?
liveforphysics
100 TW
swbluto said:
Fitting the center of the hole with a rod, and drilling down through both together would likely result in better results than not, as the bit would hold center.
However, taking Matt up on his very kind offer to bore the hole for you would definitely be the path to best results. Matt will clamp it into something that fixes the work in relation to the bit extremely solidly, then use continuous lubrication feed and a low spindle speed with a short fat bit choked up in a mill chuck. Or he will plot a CNC to do a circle pattern, and do it that way. Either way, it will cut the hole as cleanly as you are going to get it.
liveforphysics said:
If he does find a 14-tooth pulley that he has in stock, and he subsequently PMs me like he implied he would if he found one, there's a significant likelihood I would accept his offer (Depending on price, but my price threshold is pretty high relative to the job's simplicity. Probably low compared to prices he's been fetching lately.
).Alas, the waiting suggests he hasn't found one and so I must press onward. Anyways, I think I found some cutting oil online at Amazon.com and apparently Ace's has some?! I thought I've looked all over that store for some "cutting oil" or something like that.
I also got some digital calipers so I should be able to get exact measurements now. I primitively measured the diameter of my motor that supposedly has an 10mm shaft and I found its diameter to be a little over 9.6 mm (Maybe it's because I've sanded it down so much). I then measured the original diameter of the timing pulley I've been using an it's 10.1 mm, so that may have something to do with the play.
liveforphysics
100 TW
Yep. Those things need to be within 0.1mm at the most.
I like to set them for negative clearance, and then buy $1 of dry ice to set the shaft on in a little cooler, and heat the outside part on the stove until it's maybe 500deg, then quickly slide them together with no lube. Generally want to make a ghetto jig, like clamping the shaft in a vise at the correct install height, then slide them together quick.
That same method taken to a little greater temperature extreme is good enough to secure the wheel on a train to it's axle.
Again, it's more of a "final assembly" method, not to be removed again.
I like to set them for negative clearance, and then buy $1 of dry ice to set the shaft on in a little cooler, and heat the outside part on the stove until it's maybe 500deg, then quickly slide them together with no lube. Generally want to make a ghetto jig, like clamping the shaft in a vise at the correct install height, then slide them together quick.
That same method taken to a little greater temperature extreme is good enough to secure the wheel on a train to it's axle.
Again, it's more of a "final assembly" method, not to be removed again.
liveforphysics
100 TW
Miles said:
OMG, yes, 3 flute drill. I totally forgot to mention that. Thank you Miles for being awesome in all things. 3-flute drills center themselves with pressure correctly without needing to sit in the self-created cone shape that a 2 flute drill sits in to center.
Or, how about:
Use a 1/4" shaft in the drill chuck to center the machine vice.
Fix the pulley on the 1/4" shaft (with pre-centred end), using the grub screws. Fix the shaft in the drill chuck - pulley hub nearest chuck.
Drill through until you get to the hub and then cut off the hub with a hacksaw - or remount the pulley in a machine vice and drill out the hub.
Just thinking aloud, here......
Use a 1/4" shaft in the drill chuck to center the machine vice.
Fix the pulley on the 1/4" shaft (with pre-centred end), using the grub screws. Fix the shaft in the drill chuck - pulley hub nearest chuck.
Drill through until you get to the hub and then cut off the hub with a hacksaw - or remount the pulley in a machine vice and drill out the hub.
Just thinking aloud, here......
liveforphysics
100 TW
http://www.drillbitsworld.com/3_Flute_Drills-8mm_3_Flute_150deg_Self.html
That would let you make a pretty good hole in your pulley just with a drill press and holding the pulley in a pair of vise-grips on the table. Pressure lets it actively center the hole. Unfortunately, you could probibly buy a whole new scooter for the price of the bit. Be glad you don't have to drill a 3/4" hole in a pulley with a 5/8" bore. $638 just for 1 pocket sized drill bit.
So many times with projects it becomes cheaper, and results in better outcome, to let a machine shop handle certain tasks.
If I were at my dad's place, I would chuck it in a lathe centric to the OD of the pulley, set the boreing bar for a 4mm radius, and run it inside. Boreing bars don't care what size the whole was previously.
That would let you make a pretty good hole in your pulley just with a drill press and holding the pulley in a pair of vise-grips on the table. Pressure lets it actively center the hole. Unfortunately, you could probibly buy a whole new scooter for the price of the bit. Be glad you don't have to drill a 3/4" hole in a pulley with a 5/8" bore. $638 just for 1 pocket sized drill bit.
So many times with projects it becomes cheaper, and results in better outcome, to let a machine shop handle certain tasks.
If I were at my dad's place, I would chuck it in a lathe centric to the OD of the pulley, set the boreing bar for a 4mm radius, and run it inside. Boreing bars don't care what size the whole was previously.
John in CR
100 TW
Gotta make friends with a 1 man or small machine shop till you have all your own machining tools.
John
John
Okay, I didn't realize this would be so difficult/improbable to do accurately. I could order two pulleys and see if the first one gets reasonable results and then have the second as a future replacement if it succeeds or I take the other one to the machine shop if it doesn't, or I could just order one and take it directly to the machine shop.
The cost of an extra pulley is ~$10. Acquiring the required tools and equipment is probably going to exceed $5, although I could probably drill it to an undersized imperial approximate using an existing drill bit and then *gasp* file the rest until it fits. I'll have to be more careful with the filing this time.
It seems getting in guaranteed to be right the first time is cheaper. But I'll order that backup pulley just in case...
The cost of an extra pulley is ~$10. Acquiring the required tools and equipment is probably going to exceed $5, although I could probably drill it to an undersized imperial approximate using an existing drill bit and then *gasp* file the rest until it fits. I'll have to be more careful with the filing this time.
It seems getting in guaranteed to be right the first time is cheaper. But I'll order that backup pulley just in case...
John in CR
100 TW
Could you use the motor to spin the axle and crudely machine the axle down to the size needed?
John
John
John in CR said:
Problem is finding those kind of machine shops nearby!
Well, none of them are going to be nearby, so that's not a deciding factor.
The other part is finding a "1 man" machine shop. It doesn't seem like they advertise. The ones in the yellow pages seem to be small to mid-size machine shops, so I'm going to guess that'll be my best bet.
I meant that drilling undersized and filing out wouldn't be a good idea.
If you want to have a go at drilling it out, for the experience, I don't want to put you off.
Best to either use a 3 flute drill or mount the pulley on a soft steel rod and drill through rod and pulley together.
If you want to get someone else to do it, take up Matt's offer.
If you want to have a go at drilling it out, for the experience, I don't want to put you off.
Best to either use a 3 flute drill or mount the pulley on a soft steel rod and drill through rod and pulley together.
If you want to get someone else to do it, take up Matt's offer.
Miles said:
It seems only imperial drill bits are available. If I were to go up one size, I would have to order a special 15/32 inch size according to this drill chart: http://bobmay.astronomy.net/misc/drillchart.htm, but I'd overshoot the shaft size by .3 mm which liveforphysics seems to think is intolerable. That's going to equal some big bucks for something I'll probably use once. The alternative is to order a metric drill and that's also going to equal some big bucks for something I'll use once.
So it seems like "undersizing" it and doing whatever special after that is the only way to get within .1 mm that would justify not hiring a physically local machinist. (Getting a special drill that I'll use once it would justify the use of a physically local machinist.)
Hmmmm... John seemed to have a good idea. What about enlargening the bore to something slightly undersized and then spinning the motor and reducing the motor's shaft diameter to fit (Using a flat file for the reduction mechanism)? Would that likely get it within tolerance for a n00b?
Miles said:
Oh, cool! That's an awesome site. I'm adding that to the list!
Anyways, I'm looking for bearings and I found they had the type I was looking for.
http://www.mcmaster.com/#=3egoik
Mounted bearings! Since I take the scooter off road, I think it might be the dynamic load that killed the front motor bearing rather than the static load. So I'm looking at reinforcing the front bearing by putting an external bearing support on the other side of the pulley. I noticed the dynamic load of my bearing, http://www.bocabearings.com/main1.aspx?p=product&id=4458&n=SMR6800C-YUU_NB2, was 175 kgf which translates to 385 lbs. The above mounted bearing had a dynamic load rating of 990 lbs. Do you think that'll be enough? I'll try to mount the timing pulley so the belt is as close to the motor's front bearing as possible. If that's not enough, I was going to use a larger one like this one...
http://www.mcmaster.com/#6661k121/=3egy2q
It has a dynamic load capacity of 1901 lbs. The problem is I wouldn't know how to mount it. I think I'd have to buy a separate 35mm drill bit *just* for it to create the "bearing tube"; a regular drill bit would leave a conical impression in the material, though. I'm not sure if bearings take well to that. Also, do you think a double shielded bearing would be good enough for off-road if it's near (but not directly in-line like the motor's front bearing) the dirt-flinging wheel?
