Thursday, November 17, 2011

Finishing the steering stem

It was way back in July that I turned the blanks for various length steering stems.  The various lengths allow me to adjust the amount of dive that happens under braking.

Here's where we left these parts:

Now these parts will be brought to the 4 axis mill and have the pivot holes and clamping faces machined.  then i'll switch to another setup and trim and chamfer the ends.

The first step is holding the parts in a 3J collet on one end and with a dead center in the other to ensure the part axis is coincident with the mill 4th axis.  That means that the zeroth step is to align the dead center to the 4th axis.  I machined a round adapter that helps greatly in this process:
I then remove this mandrel, reinstall the dead center quill and then clamp a part:
To check the alignment I held a .0001" indicator in the mill spindle and rotated the 4th axis.  the part was within .0003 TIR, which is an excellent runout for a 2nd operation clamping.
Now that the part is properly clamped and in alignment I can machine the features that mount the upper and lower control arms.  the machining is 4 pocketing routines and 2 reamed hole routines ending with the almost complete part:
Repeat this a few times with appropriate modifications for the various lengths and i have a bunch of useable parts:
Now there is a simple cleanup operation to do on each side to round and smooth the ends.  The part is held in the 4th axis in a 3J collet with the end just sticking out.
I profile the end, then chamfer it and repeat for both ends top and bottom:
The finished parts are pretty sweet lookin:
 Especially when assembled in the spider:
That's one more part to cross of the to-do list.  The front end is starting to take shape, i'm only missing the control arms which are next on the list of complex parts to do.  I may try to squeeze in a few simple parts before that, let's see what the next week or 2 bring.

That's all for now.

Monday, November 14, 2011

Front end assembly

Now that the spider machining is done I can bolt the legs on and hope the axle holes line up!
As expected both legs fit properly and the axle is a nice smooth sliding fit through both legs.  The assembly looks pretty cool, especially compared to the simple previous design.
Once I finalize the rim/brake rotor combination the radial caliper mounting holes can be machined in their proper places.  The calipers are the dual Brembo radial mount big pad CNC versions (with the radial caliper too) which will be total overkill for such a light bike, but we like overkill on the brakes, which should be the bike's strongest point.  Why Brembo?  They are the best.  Period. I got them from Fred Renz at Yoyodyne who has a huge selection of high end parts at good prices.  Rims, brakes, bodywork, slipper clutches, etc.  No waiting for drop shipping from the manufacturer, he's got it all in stock.

The rotors are Brake Tech Iron Rotors that use a different method than the usual round button to transmit the braking torque from the rotor blade to the carrier.  When we were running the Ducati/Rotax single which only had one front disc the buttons on various name brand rotors were constantly being galled and requiring replacement. Once I switched to the Brake Tech rotors all wear was eliminated.
In this photo you can see the flat surfaces that transfer the load.  The buttons are merely for axial retention.  All the parts are finished to a high level of detail with a nice even anodized finish.  The rotors are even cryo treated!

They are definitely a manufacturer I recommend when replacing brake rotors.  If you have deeper pockets they also make a ceramic matrix composite rotor that works great on the street.  It is super light and great for a track day bike but unfortunately not allowed by most race organizations.

Next post will be the 4th axis work on the steering stem, hopefully in a day or 2.