[Adrian Wintle]

I've been playing with the Richta app a bit, and if you have an android device with GPS, it seems like a pretty good option, certainly for a worker who doesn't want the big investment of buying hardware.

As long as you are in terrain where you can consistently get a GPS signal. As soon as you start having GPS dropouts or multipathing your accuracy goes to ****.

I used to run a Terratrip 202 in my street car/rally setup vehicle. Odo probe (mech odo) or wheel probe (on the driveshaft) depending on the car. I never had any issues with it (nor competing with any number of Terratrips*). Your stock odo is usually accurate enough, but it is nice having a programmable odo for when you are on the other side of the border and working in funny units.

* the only issues were due to the car preparer (bad power connection, bad probe connection) or the road (probe and bracket knocked off by a rock).

Adrian

 

[Mark Holden]

As long as you are in terrain where you can consistently get a GPS signal. As soon as you start having GPS dropouts or multipathing your accuracy goes to ****.

I agree. Back ~10 years ago I ttried using a (then) high-end Garmin hand-held unit, and the accuracy went to crap in heavily wooded areas and anything twisty.

Nowdays I have a 20Hz Bluetooth-based GPS feeding an Android device, and it is a whole different world.

I used to run a Terratrip 202 in my street car/rally setup vehicle. Odo probe (mech odo) or wheel probe (on the driveshaft) depending on the car. I never had any issues with it (nor competing with any number of Terratrips*).

* the only issues were due to the car preparer (bad power connection, bad probe connection) or the road (probe and bracket knocked off by a rock).

And every issue I've seen with my Terratrip has been internal to the device itself. It is, however, old, and is probably not a representation of current Terratrip products.

I'm gonna mount a Nexus 7 tablet in place of it for Nemadji Spring, with the GPS unit mounted with a good clear view. It'll be a good test. There's no risk of getting lost on the transit, and we'll be on notes for the stage anyhow.

 

[jayn_j]

Personally, I'd go for an Alfa Checkpoint and hook to the speedometer sensor (assuming the car has electronic odo). The Alfa is reasonably priced around $200 ( http://www.rally.cc/#CheckpointStart ). It has either twin odos or an odo and a clock. The clock will stack entries, making it useful for timing at finish controls or TSD use. It is rugged and doesn't seem to have all the issues that plague Terratrips. The odo takeoff tends to be more reliable if you do a competent job of wiring and cable management.

Personally, I have Timewise products, but they cost a lot more. They are what you need to be competitive in national TSD.

Since TSD has different requirements, I connect the odo to an undriven wheel. I use an Alfa EZ-pulse and a plate that bolts to modified lug nuts. This is good for TSD, but exposes too much in stage applications. Better to tolerate wheel slip. You can still hook to an undriven wheel by mounting magnets to the wheel and using a hall effect sensor, but in that case you need to either mount magnets on all your wheels or never rotate your tires.

 

[chmsam]

If you go with a Terratrip I would suggest soldering the wires to the pins in the plug for the connections. Simple to do or you can buy a new connector and solder the wires to accomplish the same thing. Much more durable than crimped wires.

I'm going from the ancient one I had but by doing that I didn't have any problems until the backup battery failed. Anyone else I knew who had one and soldered the wires to the pins also had no troubles.

I also really like the Alfa Club. You get a clock (seconds or hundredths) and an odo for a pretty good price. You can use the Club with a battery and handhold it if you just need to use a clock (that's very nice for doing work at TSD's).

I've used GPS but most folks don't update often enough and of course in really bad weather or heavy folliage like in some spots at STPR you might have a chance of not being able to read enough satelliltes. That is just a "maybe" though.

 

[Audi UrQ]

Personally, I'd go for an Alfa Checkpoint and hook to the speedometer sensor (assuming the car has electronic odo). The Alfa is reasonably priced around $200 ( http://www.rally.cc/#CheckpointStart ). It has either twin odos or an odo and a clock. The clock will stack entries, making it useful for timing at finish controls or TSD use. It is rugged and doesn't seem to have all the issues that plague Terratrips. The odo takeoff tends to be more reliable if you do a competent job of wiring and cable management.

Personally, I have Timewise products, but they cost a lot more. They are what you need to be competitive in national TSD.

Since TSD has different requirements, I connect the odo to an undriven wheel. I use an Alfa EZ-pulse and a plate that bolts to modified lug nuts. This is good for TSD, but exposes too much in stage applications. Better to tolerate wheel slip. You can still hook to an undriven wheel by mounting magnets to the wheel and using a hall effect sensor, but in that case you need to either mount magnets on all your wheels or never rotate your tires.

It appears Alfa's Checkpoint Start has been replaced by their Club model. It's unclear to me from reading the Club model manual whether the Club has the capability to do remote zeroing of incremental distance, though I'm sure a quick email to the manufacturer would shed light on that issue. Also, if you mount the magnet to the hub, rather than the wheel itself, and the sensor to a fixed nearby object e.g. brake shield dust plate or suspension mounting point, then you don't have to worry about mounting magnets on all your wheels or never rotating your tires.

 

[jayn_j]

It appears Alfa's Checkpoint Start has been replaced by their Club model. It's unclear to me from reading the Club model manual whether the Club has the capability to do remote zeroing of incremental distance, though I'm sure a quick email to the manufacturer would shed light on that issue. Also, if you mount the magnet to the hub, rather than the wheel itself, and the sensor to a fixed nearby object e.g. brake shield dust plate or suspension mounting point, then you don't have to worry about mounting magnets on all your wheels or never rotating your tires.

Yes, I misquoted the proper Alfa Club model name. I can verify that the club can do remote zero.
The issue with mounting the magnet on the hub is that heat can cause these rare earth magnets to temporarily lose their polarity. If you are in a situation where the brakes are glowing (hey, none of do THAT, right?) you can find yourself missing pulses, or in extreme cases frying the magnet entirely. It is a tradeoff. For AWD, taking the sensor off the odo output is kind of a no brainer, or at least using the transfer case differential input as a mounting point for the magnets. On FWD, the rear axles can be made to work, since the rear brakes don't tend to get as hot.

 

[Audi UrQ]

Well, the hub is mentioned by Alfa themselves as one of the possibilities. But there are also other options like axleshafts, driveshafts, etc., in addition to mechanical speed probe sensors or tapping into the car's digital VSS, if it has one.

 

[jayn_j]

Well, the hub is mentioned by Alfa themselves as one of the possibilities. But there are also other options like axleshafts, driveshafts, etc., in addition to mechanical speed probe sensors or tapping into the car's digital VSS, if it has one.

The heat issue is something that many of us have learned the hard way by losing the odo after overheating the brakes. Folks, please trust me that it happens and consider this when placing magnets.

Placing magnets on a driven wheel is generally easier as you can use halfshats, driveshats, the differential, etc. In stage events there will be slip on either end. If you choose a driven axle, your measurements will tend to be long. If you choose an undriven wheel, you usually come up short. Long is better for stage as you can simply pause the odo until the landmark shows up. The undriven wheel is better on TSD or layout because you are not doing the hard braking that causes the undriven wheel to lock up. That lockup is what causes the short measurement.

For the vast majority of those reading this who are considering this for a course car or stage application, simply use the VSS output for the speedometer. There is a lot of info on the net about connecting to this, and I believe there are even kits out there for Subies. The VSS is especially nice because it is rugged and protected from the nasties that eat magnets.

 

[X Mon™]

For the ~2007 and earlier Subarus with an electronic Odo, no "kit" is needed. The VSS wire may be tapped at the ECU, which is under the front, curb side carpet.

For later Subarus that use the ABS system CAN signal for vehicle speed, we have successfully taped the VSS wire feeding the DCCD (center diff) controller, at the control module.

 

[wgl]

Pirating signals from OE Vehicle Speed Sensors (VSS) can yield very reliable signals if done carefully. I have done this for over 20 years, primarily to operate Alfa and Timewise rally odometers for high level TSD rallying.

The problems associated with attaching magnets to hubs (thermal demagnetization, and magnet loss due to adhesive degradation) can be mitigated by using self-biasing Hall Effect gear tooth sensors aimed at ferrous "targets" (wheel studs, bolt heads, projections on inner C-V joints, etc.).

I have been experimenting with a device to extract VSS signals from the onboard diagnostic ports (OBD-II, CAN and earlier ISO signal standards) on all recent US market cars and light trucks. The VSS signal must be divided down to operate rally odometers in their normal calibration range. This can be done with an external frequency dividing circuit, or, in the case of Timewise rally instruments, with the standard or optional internal frequency dividing circuitry.

There is full time +12VDC and a chassis ground available in the OBD-II port, so it's possible to have a "plug and play" rally odometer setup that can be installed in most cars in a matter of minutes. Really handy for running Car 0/00/000.

Greg Lester

 

[DatsunZguy]

THANKS for the great info folks! I am getting more and more stoked to move in the direction of the Alfa Club due to the extra options of timing -- as compared to GPS options. For now, I have to concentrate on STPR prep, but soon after I'll be looking into the OBD2 port possibilities or the VSS at the ECU as Matt has suggested. Thanks again, to all. I haven't forgotten that this is overkill for most rally work, but I harbor a small seed of hope to someday co-drive, so learning the basics of some of this technology cannot hurt.