OzVMX Forum

Clubroom => Tech Talk => Topic started by: FAT-TOY on March 30, 2011, 05:37:26 pm

Title: Starter rolls
Post by: FAT-TOY on March 30, 2011, 05:37:26 pm

  Building a set of starter rolls using a 9 inch grinder to run it.  By my calculations if I use a 50mm roller driven directly from the grinder. The roller will spin at a speed of about 60 kph,  this will mean that the bike would need to be started in a higher gear.  Can anyone who has one or has used one let me know if this is the case?

  The calculations I used are ( Roll 50mm or 0.05 of a mtr times Pi (3.1416) =0.157mtr x6500 revs of the grinder = 1021 mtrs per minute x 60 to convert to hours = 61261mtrs or 61.261kph.

   I think that 50mm is as small as I could go with the roller and still get drive onto the tyre.  If anyone can give me any additional information it would be appreciated.
                                                                Zane 

Title: Re: Starter rolls
Post by: tony27 on March 30, 2011, 05:51:52 pm

Are you talking about direct drive to the roller?
I would have thought gearing the roller down would be better for the life of the grinder

Title: Re: Starter rolls
Post by: NIF on March 30, 2011, 07:08:24 pm

Just a little more info for your overall design Zane, They're using a car to drive theirs, but the rollers and bearing mountings caught my eye, check out this configuration. http://www.andersonstands.com/gallery/workshop/Starting_rollers_AS2019.htm

Title: Re: Starter rolls
Post by: FAT-TOY on March 30, 2011, 07:24:57 pm

  
    Tony i'm not locked into anything as far as design goes yet,  I have the grinder and I  can machine the rollers to any size,  so I have put it out there for comment.  In saying that the only photo I have seen of this configuration was a direct coupling of the grinder to the roller.    If anyone on this forum has built or has a photo of (a do it your self) set I would be interested to hear from them.  The professionally built rolls are far to expensive.
                                                                                                                  Zane

Title: Re: Starter rolls
Post by: tony27 on March 30, 2011, 07:44:47 pm

Just had a quick look at the in pits photos on livewire from whakatane to see if there was a good shot of the roller set up used to start the ccm, all I really remember about it was that it used a starter motor.
Have a look for the shots of #55 in the pits & see if you can get some ideas

Title: Re: Starter rolls
Post by: Mick D on June 29, 2012, 11:06:27 am

Hi Zane, how is that starter roller coming along mate?

Any chance you will have it be ready for the Crawford River Classic on the 14th July 2012?

Title: Re: Starter rolls
Post by: matcho mick on June 29, 2012, 12:32:59 pm

sook  ;D,fix yer ankle yet ::), :P

Title: Re: Starter rolls
Post by: FAT-TOY on June 29, 2012, 09:34:59 pm

  Hi Mick
            It's been on the back burner for a while. Had it almost finished, looks great is compact easy to store and carry but still needs some work.  The roller which turns the wheel needs to be larger so it wont lose traction with moto-cross type tyres and that means it will have to be geared down.  Bigger diameter roller spinning at the same revs would have the wheel turning far to fast.  I also have to find something to coat the roller with that will help it keep contact with the tyre.  Going to have a talk to a mate in the retreading business about maybe gluing a spiral section of tread around it. Anyway it's all fixable but might not be ready for Crawford River.   I will try to attach a couple of photos.
                                                                                                                                                      Zane.

 (http://i907.photobucket.com/albums/ac276/zane255/StarterRolls009.jpg)

(http://i907.photobucket.com/albums/ac276/zane255/StarterRolls004.jpg)


(http://i907.photobucket.com/albums/ac276/zane255/StarterRolls001.jpg)

Title: Re: Starter rolls
Post by: VMX247 on June 29, 2012, 09:42:56 pm

Would the skate board decking be enough grip ! 8)
http://ozvmx.com/community/index.php?topic=7229.15

Title: Re: Starter rolls
Post by: FAT-TOY on June 29, 2012, 10:01:55 pm

    Tried step tread which is a similar product on the small roller and it gripped a little on road treads, but the bike I used had very low compression (stuffed) and even then it tended to act like a grinder on the tyre when the clutch was released.
             Zane

Title: Re: Starter rolls
Post by: Curly3 on June 29, 2012, 10:17:52 pm

A friend of mine rides both Classic Road Racing & Dirt Track, he bought an over the counter set of rollers that worked perfectly on his road bikes, brought it out for a test session with his new DT bike and it pretty much destroyed the brand new, soft trials tyre he uses on DT.
A roller that is set up to suit a DT & MX type tyre would also suit a road tyre but won't work the other way round.

Title: Re: Starter rolls
Post by: pancho on June 30, 2012, 09:47:01 am

I think the answer may be to somehow set up an endless strap system between two rollers with the strap slack enough between the rollers to conform with the radius of the tyre. The problem to overcome then would to enable adequate grip between the drive roller and the inside of the belt/strap.
 Not my idea but one I got from Lou D.
 Cheers pancho.