Deeluxe boot tuning (SAB----->MAB)

Post by **tufty** » Tuesday 18 December 2007, 22:34

All of the dimensions asked for are explained in Simon's original drawings (last post of the thread linked in the first post) or elsewhere in that thread.

Beware the last drawing that claims the dimensions for the bottom part are inches. That's liable to leave you with a large and useless piece of aluminium :)

(another) Simon

Post by **kurtsk8** » Tuesday 18 December 2007, 22:40

tufty wrote:That's liable to leave you with a large and useless piece of aluminium

that's important

hope to have a good calculator

Post by **pokkis** » Tuesday 18 December 2007, 22:44

Dimensisons are in millimeters in picture so dont convert them

Drawing says that they are in inches but they are in millimeters.

viewtopic.php?p=17212#17212

Post by **kurtsk8** » Tuesday 18 December 2007, 22:46

in fact, i've just seen them

thanks

Post by **kurtsk8** » Tuesday 18 December 2007, 22:59

and......
what about springs and axis?

would someone suggest me again please???

Post by **voodoo** » Wednesday 19 December 2007, 9:10

o great --- i am looking for this draws --- i have alu. and springs ...

now i can start with produce

Post by **tufty** » Wednesday 19 December 2007, 10:13

kurtsk8 wrote:and......
what about springs and axis?

would someone suggest me again please??? :P

Simon's drawings suggest M6 for the axis, there was discussion in the other thread that it might be possible to emulate the northwave forward lean adjuster using an M6 thread for the bottom part and M8 for the "active" part, drilled and tapped for the M6 bottom part and with a lip at the bottom to carry the spring. See page 2 of the other thread for details. A simpler approach to achieving the same thing would be to use a single M6 with a preload adjuster nut at the bottom (and possibly to use a shorter "rear lean" spring), although it means your preload adjusters are in different places. Yeah, like that really matters :)

Marco's spring specs (uncompressed) are in the first post of this thread (89 or 76mm for the top, 25 for the bottom)

Simon, after testing, changed his springs to the ones specified here : viewtopic.php?p=16925#16925, again 89 and 25, this appears to be exactly what Marco has based his spring choice on.

Personally, I'd probably opt for a different way of locking the "axis" into the bottom fitting[1], and use the space previously used for Simon's locknut for a bottom preload adjuster instead, thus keeping the same spring lengths overall.

Assuming you have 89 & 25mm springs, your axis length is going to be, more or less, 8mm (bottom fitting) + 6mm (roughly the thickness of an M6 nut) + 25mm (bottom spring) + 6mm ("blade" of the main part) + 89mm (top spring) + 12mm (a couple of locknuts / preload adjusters) plus 5mm for luck and washers, i.e. 150mm or so

And, of course, you'll want a teflon tube or similar on the axis itself, long enough so it can slide, but short enough not to stop you being able to use the preload adjuster(s).

Simon

[1] Probably involving machining the bottom part from stainless rather than alu, and gas welding the axis in place. A "through" lock bolt would seem likely to weaken the structure, and loctite is unlikely to hold given differing coefficients of expansion between stainless (the axis) and alu. another option might be to "key" the axis in the bottom piece or to slightly chamfer the hole at the bottom of the bottom piece, then simply peen the bottom part over to make it "wedge".

Post by **floatingmatjaz** » Thursday 20 December 2007, 17:53

I would suggest M8 for the axis, if you will use normal A2 inox steel (the one you find normally in shops)
Expecially if you plan to use your homemade BTS sometimes with some stiffer springs (...for normal carving...)
I managed to bend an M6 on the home carpet on my first prototype BTS... with medium springs mounted on it (same stiffness as Bomber's medium)

Post by **kurtsk8** » Thursday 20 December 2007, 18:00

is there any possible problems mounting a system like Simon's one where you have to dig a hole in the back part of the boot?
I would prefer not to modify boots

many many thanks

Post by **Simon** » Friday 21 December 2007, 9:06

The auxiliary mounting holes are only necessary for the backward movement, because otherwise the upper aluminium part can bend outwards and there is the risk of bending the axis. With these two extra screws the system is mechanically well defined.

The two holes in the plastic of the boot are really not a problem. The stiffness of the boot is for sure not reduced.

An M6 axis is sufficient, for the forward movement the axis is charged on pull, only on backward movement on push, but there lever is short. Till now, I rod my boots with the SAB more than 100 days without bending the rod.
But you have to give attention to less enough play in the systems, that the rod can move free over the hole movement range.

An other reason for the M6 axis, I wanted to have a very compact spring system, with an M8 bolt the spring diameter is rather bigger and it's not possible any more to hold the system as compact as it is.

simon

Post by **kurtsk8** » Friday 21 December 2007, 10:21

Thanks Simon

Post by **floatingmatjaz** » Friday 21 December 2007, 12:25

@simon
sorry, you're right! Your system has a very short lever, so i believe M6 is enough...

I have much longer lever on my BTS, that's why M6 was not enough for mine!

But question... Have you ever mounted harder springs on yours?
bye

Post by **Simon** » Sunday 23 December 2007, 12:06

yes, I don't use the springs I mentioned in my first post any more, have a look to my sab topic last post. Even if I would use much harder springs, there isn't any side load on the rod, the load is charged only on pull (except with the back spring, but this one is very short).

simon

Post by **floatingmatjaz** » Wednesday 26 December 2007, 12:03

Your system is truly well engineered!

bye

Post by **montefuca** » Thursday 27 December 2007, 8:06

Simon wrote:yes, I don't use the springs I mentioned in my first post any more, have a look to my sab topic last post. Even if I would use much harder springs, there isn't any side load on the rod, the load is charged only on pull (except with the back spring, but this one is very short).

In your opinion, which improvements could be made on your system?