vp hurtz shifter dig
 

im using an old ko propo mars ex-1 remote that has a 2 position switch. how do i set trim setting for vp hurtz shifter dig. i fried my servo for dig already and dont want to fry another.

You set it up for dig and 4wd... You will not have free wheel, which is no big deal..

Don't set the throws with the linkage (servo horn) connected. Ease your throws and put the servo horn on to check them, that way you don't fry it with too much throw..

If your Mars EX-1 is the same model as mine, it doesn't have adjustable end points (EPA) on channel 3.

You've got 4 choices:
Find a servo arm and linkage that are exactly the right length.
Get a digital servo and matching programmer. You can use the programmer to set the EPA directly on the servo.
Get a new radio with EPA on ch3.
Build a new radio, using the Mars case and the electronics from a 6-channel airplane Tx. There are several threads on the electronics forum about building Txs.

Another option that might work is a Punk RC dig switch. No idea if this will work properly with the standard Mars, because it's only got "soft" momentary buttons for ch3.

how would i know what the exact lenght and servo horn to use

or you could add potentiometers to each leg of the switch. this will allow you to adjust. that is, if it works like a TQ3.

whats the easiest way and cheapest fix for now, i was planning on getting ko propo ex-5ur in couple of weeks when they come in. thanks for the help by the way

Trial and error. Start with a very short arm at the servo end of the linkage, being very careful to make sure that the servo doesn't bind at either end. Keep increasing the servo arm length (or decreasing the dig arm length) until you get full movement at the dig, without the servo locking up. Adjust the linkage length to balance the servo between the 2 end points.

Not sure if adding EPA pots will work with the Mars. It doesn't have a dedicated switch for ch3 - you have a choice of 2 switches (maybe 3?) and you program the Tx with your choice. If this switch is just a logical signal to the microcontroller (which it likely is), adding pots won't affect the throw.

or you could get one of these.... It's what I had to do with my JR Z-1 / KO Helios

http://www.servocity.com/html/180o_servo_stretcher.html

They are a bit fiddly to get set up, but they work.

Wow - an adjustable stretcher. Not seen one of those before here in the UK. Useful piece of kit.

got linkage almost perfect but when i engage dig servo still can turn about 1/16.



i want to throw my truck against the wall already

You really should have a remote with end point adjustments. That would save you all the headache you are facing now.

For my Hurtz Dig, I have my 4WD end point adjusted so that if the engagement points are exactly aligned, the servo is still pushing it forward until I drive slightly and then it locks in to place and then the shifter rests a mm or 2 from the edge of the dig case. For my RWD Locked (all the way back on the shifter), I adjusted it so it would only have a light force on the servo if the engagement points are exactly aligned, thus, when I drive slightly, the rears will lock into place fairly easily since they aren't powered and rely on the dragging action to make that final engagement. I only have a 2pos 3rd channel on my radio as well, though I have end point adjustments on that channel. It took me just a few minutes to get it tuned in a working the way I like.

Not sure if this helps or not... Also if you are in the market for a new radio, keep an eye out for the new Futaba 3PM-MX that Harley showed off in the electronics forum here. If you are getting into digs on your crawler, a good radio is a must IMO. My JR XS3 has seen it's time for me, and I am ready to make the change to a nice 2.4Ghz system, like the 3PM-MX.

SS