Need Machinist Help

Mr.GhettoRig

Mr.GhettoRig

Active Member
#1
#1
Might be getting a little too serious about my weed eater bike... I can never seem to leave things alone.

The bike is friction drive and since the first ride I've been trying to come up with a solution to the drive spindle where I can have good traction to the tire in wet or dry.. I've tried just about everything from sockets to PVC with mixed results. The solution that seemed to work the best was a plastic twist grip over my 3/4" socket spindle. It grabbed flawlessly through every puddle, but on the way home from work the same day it shredded completely and left me back at the drawing board. The knurling on the grip worked perfectly in getting the grip I wanted so I went hunting for a chunk of cylindrical metal that was knurled and the only thing I could come up with was the spindles for the staton inc. kits which aren't compatible because I'm running a 25cc Homelite with no clutch to thread the roller into.. so it was back to the drawing board again... After some pretty messy sketches and a couple hours on autocad I came up with this....



I've always thought it'd be cool to have more than one speed, more or less just for the sound of shifting "gears". Basically the roller/spindle will run on 1/2" square stock controlled with a shift fork that will be cable activated by a suicide lever. I'll have a return spring riding on a collar in front of it to push it back to first gear when the lever is disengaged. Looked good on paper so I figured i'd give it a shot, at the very least I'll have a nice desk ornament I can say I designed. With all that said if anyone has any pointers they can throw my way about functionality that would be really helpful. One of the things I was curious about was clearance between the square shaft and the spindle itself. It's currently set to exactly a half inch but I don't know if 1/2" square stock will fit inside with the spindle able to slide smoothly. And also I'm not sure I'm entirely happy with the knurling in the model so I'll have to go back and fix it later as well as dimension everything.

My next obvious concern is I don't own a lathe to even begin making this thing. I looked on evilbay and found some steel 1-3/4"ID-6" round stock for pocket change that might work. But I'm a newbie when it comes to metals so I'm not entirely sure what to look for. I figured I'd ask around on here because I know a handfull of our members own the equipment and are talented with projects like this. I'm trying to avoid being ripped off by a local machine shop but I'm willing to pay for everything from shipping, materials, and hours. I'm really looking forward to making this happen, if anyone is willing to help out or point me in the right direction I'd be really greatful.. I figured I'd start my hunt on one of the best sites on the web. :thumbsup:

Hope to hear from you guys soon.
 
Last edited:
Oldsalt

Oldsalt

Well-Known Member
#3
#3
The part would be easy if it were not for the 1/2" square hole. A 1/2" square broach would be an expensive item. Perhaps solidly fix the drive roll to the engine output shaft and move the entire engine right and left? Looks like a patentable item.
 
bigrob

bigrob

#4
#4
As oldsalt mentioned the hard part is the square peg in the round hole scenario

What if you used a piece of square tube with 1/2x 1/2 inside dim
Then find some hubs , shaft collars of even pipe that slip or press over the square tube and weld it up
 
TANKSAREUS

TANKSAREUS

#6
#6
GR - Can you send a pic of what you have on the bike at present. Just want to see where it goes and what it does. Will see if I can knock something out on the lathe for ya.
 
Mr.GhettoRig

Mr.GhettoRig

Active Member
#7
#7
hey guys.. I downloaded the program from that site but haven't had any time to mess around with it. based on their sample project prices I think thats the best way to go, I estimate it'll be around $60-$80 plus shipping which is pretty reasonable and far less than I was expecting.

Tank, I got you a picture of the drive spindle as of right now. it's a couple galvanized pipe fittings and it doesn't work all that great but with the size I'm able to get around 35mph top speed which is way better than the socket spindle I was using. The idea is that the square shaft will thread right to the flywheel like the spindle currently is, and the piece I need machined is a collar that rides on the square shaft. I can make a sketch of the full assembly whenever I get the time.

Not the greatest picture in the world but it gets the idea across.



As for the drawing itself goes, aside from fixing the knurling I'm still curious about the clearance between the square hole and the actual 1/2" square shaft. Should I keep them both at 1/2" or make the square hole a couple thousandths bigger? :shrug:

Thanks for all the help guys. I can't wait to make this happen. :scooter:
 
M

mckutzy

Member
#8
#8
I found out about this tool a few years ago and there is a few variants you can build yourself with a drillpress. Just need some knurl wheels.
I think they call it a nutcracker knurler, hand knurling tool.

There is a few out there that people have modified pipe cutters, and put knurling wheels in them.





 
TANKSAREUS

TANKSAREUS

#11
#11
Been thinking alot about this little project GR. Have a simple solution for us guys without high tech equipment.
Weld together four pieces for flat stock, then turn up on the lathe. The blocks can always be strengthened by welding the seems after turning. Let me know if you want me to have a crack at it. Will just need some outside dimensions and a lenght.

 
Clayon

Clayon

#16
#16
I'm coming into this late so I'm sorry if this is a stupid question, but why does there need to be a 1/2" square hole through this? Isn't the pto round?


Sent from my iPhone using Tapatalk
 
Boomstick

Boomstick

New Member
#17
#17
TANKSAREUS said:
Been thinking alot about this little project GR. Have a simple solution for us guys without high tech equipment.
Weld together four pieces for flat stock, then turn up on the lathe. The blocks can always be strengthened by welding the seems after turning. Let me know if you want me to have a crack at it. Will just need some outside dimensions and a lenght.
Click to expand...

FWIW, I don't know if you could get away with welding several flat sections together & then turning them down. If you weld, and then turn it down, I don't know if the weld would have penetrated far enough to give you good adhesion after being turned down (you might be left with a weld about as thin as rice paper).

I would be uncomfortable spinning that on an engine, much less something that can do 7000-8000RPM's.


Good idea though, who knows, it may work. :smile:
 
Mr.GhettoRig

Mr.GhettoRig

Active Member
#18
#18
sorry I haven't been around guys, my job is good at keeping me from my hobbies :hammer:

Tank, I'm PMing you a sloppy concept sketch right after this post. And Clay, the PTO is round but there will be a square shaft that threads on to it. the spindle will slide on the square shaft.

I can't thank you guys enough for the help. :thumbsup:
 
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