Thread Tools
This thread is privately moderated by Jack Crossfire, who may elect to delete unwanted replies.
Jan 26, 2007, 02:55 AM
Registered User
Jack Crossfire's Avatar
Thread OP

Most wanted setscrews

FYI, all the set screws are lock tightened of course. Don't have the balls to put threadlock on a shaft because of the risk of threadlocking the $100 bearings.

No matter how tight they are, they naturally come lose as a function of routine stresses, but exactly which set screws come lose the fastest is still being discovered. The forward tail pinion came lose after 12 hours. The motor pinion came lose after 45 hours. All the others have been solid.

Since flattening the tail wire, the tail pinion has never loosened. Still undecided on grinding the $100 motor shaft.

The motor set screw is particularly hard to reach, requiring dismantling the spur gear & motor to get at. Being a fat shaft made it the least likely to slip but it did. Also stripped a set screw in the spur gear during yesterday's replacement, so they can be overtightened.

In other news, after giving up on CAPS, free JTAG tools, and starting to write a JTAG programmer from scratch, finally started getting something resembling useful JTAG results. The trick is the way the JTAG "taps" are wired in hardware.

With the STR9 came a diagram showing the 3 devices contained in the STR9 package and how the JTAG signals are connected to them. TCK, TMS, and TRESET are parallel, meaning all 3 devices get the same signals, simultaneously from those wires.

TDI is series, meaning the TDI signal has to bit shift through one device, then another, and another until it gets to your target device. The number of bits to shift is determined by the IR register size for each device, also on the diagram.

The ARM9 is connected to a boundary scan device with a 5 bit IR register, so when you send a command over JTAG, it's really filling 4 bits of the boundary scan device's IR register. You need to send an extra 5 bits to push the ARM9 command out of the boundary scan device and into the ARM9 device's IR register. Even more bits have to be sent to push it into the flash device.

This is all stuff you never encounter in a day job, but when you can't afford a JTAG programmer it's light reading.
Last edited by Jack Crossfire; Jan 26, 2007 at 03:20 AM.
Sign up now
to remove ads between posts
Jan 26, 2007, 01:37 PM
Registered User
jofo1's Avatar
definitely grind the motor shaft to improve set screw holding power. used many set screw spinners and always have found them to hold better when a flat was ground on the motor shaft.
Jan 26, 2007, 10:21 PM
Jack, on the idea of most wanted setscrews, well really woodscrews, but what gets me is that the hobby shops don't carry the very small sizes. I use the very small sizes that come with sub-micro servos, and I'm tired of stealing them from my servo hardware packages. I'm sure a heli guy has to have a nice collection of small hardware like this. I imagine you must order it from specialty shops.

As for prop adapters, the set screws always seem to be in the most offending location on the adapter, for the app. Murphy's Law.

As for threadlock, I wouldn't use it either. I've found that thick CA, applied with the head of a pin, after the setscrew is in place, seems to work well. I hit it with activator so that it doesn't have time to seep into the threads. Holds well enough to pervent backout, but they still come out easily if needed.

Edit, just noticed this was post #4000.

Last edited by scratchandbash; Jan 26, 2007 at 10:33 PM.

Quick Reply
Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion SAR on Americas Most Wanted CenTexFlyer Aerial Photography 30 Jun 21, 2007 05:56 AM
Off Site Nintendo Wii Most Wanted Bundle with 11 games & receipt Solcat Non R/C Items (FS/W) 3 Jan 22, 2007 02:42 PM
Discussion 12 Most wanted planes! dddriveman Fuel Plane Talk 16 Feb 06, 2006 12:56 PM
!!RCGroups most wanted!! Spencer J Site Chat 43 Nov 02, 2005 03:02 AM