Super basic 2x42 to 2x72 conversion.

Willie71

Willie71

Warren J. Krywko
Joined
Feb 23, 2013
Messages
12,214
Last week I made a simple mod to my 2x42 grinder to take advantage of the belts I bought a couple months ago for a 2x72 build I just don't have time to get to right now. Its a mild steel square extension with a longboard wheel. Total cost of this conversion is under $25.00, except I bought the wheels in a package of 4 for $35.00, with bearings. I don't know if they can be purchased individually. It took a small amount of playing with the spacer to get the tracking right. If I did it again, I would use threaded 5/16" rod, and used a nut to adjust spacing, rather than the bolt and spacer I used. I had to trim the spacer three times to get the wheel aligned and the belt within its tracking adjustment range.

Edit: As requested, the length of the extension is 19 7/8" from the back of the housing to the centerline if the longboard spindle, following the centerline of the extension just to clarify based on another post related to this one. This mod is in no way equivalent to a real 2x72. The grinder is still underpowered and runs too fast. The only advantage is the belt selection. I have a good source locally for belts and do not need to worry about cross border shipping.

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Pretty cool... but I would wonder whether or not the board wheel bearings can take the rpm of the grinder.
 
They are abec 9 bearings. I have seen some posts of others using these exact wheels and bearings for several years. If not, I have a BC bearing distributor 10min from my house, and I can get good bearings for under $5.00 each in this size.
 
Willie71 said:
They are abec 9 bearings. I have seen some posts of others using these exact wheels and bearings for several years. If not, I have a BC bearing distributor 10min from my house, and I can get good bearings for under $5.00 each in this size.
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Good stuff... I was just speculating. Did you experience any problems with tracking?
 
It took a bit of playing around with the spacer to get the tracking right. Dead steady now!
 
Not gonna lie, that is GENIUS!!

Guys for longboarding wheels, and bearings

muirskate.com bones reds are amazing bearings.

Side note, longboard wheels and bearings take spees of over 70mph no problem, I think that is faster than most peoples fastest suface feet per minute or really close to it.
 
Willie that is brilliant. I'm half tempted to buy one or two of the wheels off you in exchange for your measurements and all the info on the legwork you put into this. Admittedly I'm horrible at this kinda thing and maybe it's a dumb question but wondering if playing with the wheel size can affect the speed of the grinder.
 
medicevans said:
Willie, where did you get wheel?
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Any good skateboard shop will have a good size selection of skateboard wheels in different sizes and hardness. You should also be able to buy just one wheel if you want. If they look at you weird tell them you are building a uni-skateboard because this 4 wheel stuff is getting too easy.:D
 
Fletch Helical said:
Willie that is brilliant. I'm half tempted to buy one or two of the wheels off you in exchange for your measurements and all the info on the legwork you put into this. Admittedly I'm horrible at this kinda thing and maybe it's a dumb question but wondering if playing with the wheel size can affect the speed of the grinder.
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No, drive wheel circumference x motor speed determines belt speed. idler size doesn't matter.
 
I'll measure the length of the arm tonight and post it if anyone wants to copy it.
 
Fletch Helical said:
Willie that is brilliant. I'm half tempted to buy one or two of the wheels off you in exchange for your measurements and all the info on the legwork you put into this. Admittedly I'm horrible at this kinda thing and maybe it's a dumb question but wondering if playing with the wheel size can affect the speed of the grinder.
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I need the other three for my 2x72 build. I will post the dimensions for free for anyone who wants to try this. It took less than an hour to put together.
 
You can accomplish the same thing much more easily by simply cutting the frame that holds the upper (idler) wheel assembly, and bolting it back together with an extension made of angle iron or flat stock. All you really need is a hacksaw, a hand drill and a few bolts/washers/nuts.

All the materials you need are available at any hardware store, if you don't already have them laying around somewhere. No extra wheel to mess with, takes up the same footprint as the original instead of reaching back a couple feet, total cost about $8 and 15 minutes' work. The belt will throw swarf and grit down on top of your head (wear a baseball cap) instead of directly into your face.

Running the belt vertically does tend to grind the front off your cap, though :p
 
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I considered keeping it a two wheel design, but I have read the the length of the two wheel design tends to vibrate more. The housing isn't very sturdy to start with.
 
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