Building has start, finally...
This minibike will be a copy of my previous minibikes, except for some minor changes.
These changes have just been applied to the 3-D drawings of the minibike.
(Sorry, but measurements are in mm)
^This is the front- and rear axle of the
previous minibikes. This was machined out of a solid round (25mm diameter) piece of steel. At both ends drilled and tapped holes, to accept M10 bolts. On both sides it accepted ball bearings with an inner diameter of 20mm.
^The new minibike will be using a thick wall tube with outer diameter of 20mm. It is 10-11mm inside diameter.
Both ends will be machined to accept ball bearings with an inner diameter of 17mm. I'll keep the flat sides on both ends, they prevent the axle from turning and it works really well. A large M10 bolt will go through the axle to bolt it down to the frame. No more need to drill and tap holes.
^This is the rearaxle assembly. It's a machined 50mm diameter CrMo tube, with a sprocket adapter on 1 side, a brake disc adapter on the other side and a wheel adapter in the middle.
For the brake disc adapter I'll be using a thick wall tube (60mm outside, 39mm inside) this time. Because the new bearing (6203-2RS) has a different outer diameter, I had to redesign it.
^Redesigned brake disc adapter, ready to accept a smaller outer diameter bearing. I also added a groove for a circlip behind the bearing. Bearing is not visible, but I think you get the idea, where the bearing will be.
^No changes on the sprocket-side, as I was able to find a bearing (6303-2RS) with the same outer diameter and the smaller inner diameter.
^This is the design of my
previous bikes. The parts where the axle is slide in, had been laser cut and machined on the mill. It was a bit time consuming and there's an easier way.
^I'll just use laser cut parts. No more milling. These will be placed 3mm more outside.
^Another lasercut part will be welded to it.
The flat sides of the shafts/axles will slide right into these. It prevents them from turning and it gives more "body" to keep it all in place.
^Backside view.
Another advantage, I forgot to mention, is that bolt heads of both sprocket and rotor have more clearance this way. No more, or at least, less grinding needed.
Time to start some tube bending...
^I printed out drawings of the tube's centerlines and added the dimensions needed.
-I calculated the total length of the tube needed, added some extra length and cut them to that length.
-The length where the bents started was calculated and marked on the tube.
-The marks were all placed the same at the bending die. So length between bents should be okay.
-Over-length off tubes will be cut off later.
^Oops, something went wrong here. The marker lines are at the right spot, but 1 bent is on the wrong side of the marker line...
^We had to bent a new one, but ran out of tubing. So 2 smaller tubes were welded together.
^No one will ever know, what happened here...
^My daughter operating the manual tube bender.
^All tubes (22x3mm) bent for the minibike frame. They still need to be cut to length. And some tube notching will have to take place.
That's it for now.