Topic: Another rain gauge mod...

[aweatherguy]

I have been using the usual add-a-funnel to my PCR800 rain gauge for years now. It gives me 0.01" bucket tips and is quite accurate when properly calibrated against a manual gauge such as the Stratus. That says a lot for the OS tipping bucket design.

The only down side is that I've always been less than happy with the hacked-up look of the thing.

I recently discoverd another way to make this mod for a little more $$ with a very professional looking result. Here's a quick rundown of how to do it -- if there's sufficient interest I can post some photos.

Parts:

A) PCR800 Rain Gauge
B) NovaLynx 260-7852 Rain Gauge
C) 3 or 4 M3.0 stainless machine screws (between 14 and 25mm long)
D) 5 or 6 M3.0 nuts and flat washers

1. Go buy a NovaLynx 260-7852 tipping bucket rain gauge. The same thing is also sold under the Davis brand as part number 7852. I don't know who the actual manufacturer is, and who is rebranding. I got one for $67 plus tax and shipping.

2. Remove the tipping bucket assembly from the NovaLynx gauge. There is a single Phillips-head screw underneath to remove and then a couple of spring-loaded plastic clips (part of the base casting) must be manually retracted.

3. Remove the outer cover from the PCR800 and place the gauge in the center of the base. Line up the buckets with the drain holes in the NovaLynx base as best you can. Now, drill 3 or 4 holes with a #29 drill where the PCR800 feet are resting on the NovaLynx base plate. Two of the holes will be just out in the open, but the other one or two will be in the bottom of the water leveling trough. I only drilled one hole here so I have a total of 3 mounting holes.

4. Through the two holes that are "out in the open", install two M3.0 stainless steel screws from below and fasten tightly with a single nut on the top. This nut acts as a spacer so these two PCR800 feet will be at the same height as those resting on the rim of the water leveling trough.

5. Place the PCR800 feet over the two screws just installed and fasten with a flat washer and nut on each of the two screws.

6. Install one or two M3.0 screws from below through the other PCR800 feet (which are over the water leveling trough) and fasten loosely with a flat washer and nut. The nut is pulling on a slightly cantilevered PCR800 foot here and getting it too tight might break off the foot, so just get this snug. Add a lock nut or use nylock or crush-nuts if you're worried about it coming loose.

7. Install the NovaLynx funnel top and make sure the gauge tips. I found that mounting this way gave just enough clearance between the bottom of the funnel and the tipping bucket. I tried making an adapter plate so I could use existing holes in the NovaLynx base, but that raised the PCR800 up too high and the bucket was hitting the bottom of the funnel and would not tip.

That's it as far as I've taken it at this point. The PCR800 buckets are dumping partly onto the NovaLynx base and partly into the NovaLynx drain holes. Not all the water goes out the NovaLynx drains. I don't think this is a problem. I could try to make a couple of small channels that would get all of that water over to the NovaLynx drain holes, but again I don't think this will be an issue; the water resting on the base is probably not going to hurt anything.

I'm waiting on a predicted rain storm in the next day or two to see how it works.

[aweatherguy]

I've run this through some rain now and it works great. I think I'll call it "Franken-Rain"... 

There are two photos here showing the OS tipping bucket assy mounted on the NovaLynx base plate. I found an improvement for the screw that's in the little trough. The screw is now secured tightly to the base plate with a nut. Then I positioned a second nut on the screw level with the top of the trough -- the PCR800 rests on that nut now and a washer and third nut goes on top and can be tightened snugly without danger of breaking the PCR800 mounting leg.

There's one more optional tweak here now. The measured funnel opening on this NovaLynx gauge is about 6.55", but an 8" opening is required for the OS buckets to report 0.01" of rain per tip. Because of this the mod as described will nominally report 0.0149" of rain per tip.

A slight adjustment to the tipping angle results in 0.01" per tip. This is easy to do and easily reversible if you want to undo it. The only additional materials are two 5/16" stainless steel nuts (coarse or fine thread) and some silicone RTV sealant.

The distance across flats on these nuts is about 1/2" (closer to 0.490" in reality) and that's just the right amount to raise the edge of the bucket on each side. Just take a little silicone sealant and attach these nuts under the bucket lip on each side as shown in the photos. (Glue the nuts to the PCR800 base -- not to the bucket.) You can use many other types of adhesives too -- I used silicone because it is waterproof and comes off easily if I ever wanted to remove the mod.

Save the original OS PCR800 cover and NovaLynx tipping bucket assembly if you think you might want to return everything to stock some day.

The best thing about this mod is that when completed, it just looks like a stock NovaLynx gauge...but under the hood lurks the OS tipping bucket unit. It is a bit pricey, but some may find it worthwhile.