Rapco Belt Driven Pump

How to keep the Cessna 170 flying and airworthy.

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Lee
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Rapco Belt Driven Pump

Post by Lee »

Hi ... I just finished talking to Mark at Rapco. The 212CW-6 pumps as we know, are no longer in production and hard to find. The pumps can be overhauled if they are in such a condition that they can be overhauled. Apparently the pumps were made from different materials over their production life and that has a bearing on whether they can be overhauled. For those of us with the belt driven pump, Mark said it was important that the belt not be too tight as a belt that is too tight can cause premature wear on the vanes due to deflection of the shaft. Another interesting point ... apparently the 0-300-A like I have can have a field approval to change the accessory section (as the D has) and a splined vacuum pump can be installed ... 337 field approval is apparently not out of the question. (George or Bruce might have more info in that regard) The other item of note: Spruce carries overhaul repair kits ... Mark said that these are not really legal as there is not an approved repair kit on the market ... I am guessing that this is for certified aircraft or aircraft that are IFR certified. If anyone has any thoughts on that, I would be interested in their comments. Finally, Mark said that most people in the situation of needing to repair/replace a vacuum pump are going towards all electric ... which I have considered. (And one could go back to the venturi's) The question comes down to "coin of the realm" ... how much do we want to spend and what is the most cost-effective in the long run. I do want to maintain the airplane with an IFR capability (late afternoon summer haze in the Memphis area) and there is the matter of ADS-B compliance. To that end, I bought the Stratus Appareo and a Transcal digital encoder which will be installed shortly ... that seemed to me to be the most cost effective way to go. At any rate ... comments welcome! Regards, Lee (N1967C)

PS Mark did tell me that something they have seen is that a pump will be sent in for overhaul, it turns out the pump can't be overhauled ... the individual then sells it and the new owner then sends it to Rapco for overhaul ... you can see where this is going! Rapco tells the new owner that the pump can't be overhauled ... they apparently track the serial numbers ... something to remember about buying parts off of eBay.
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rydfly
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Re: Rapco Belt Driven Pump

Post by rydfly »

Thanks for doing the research on these old vacuum pumps.

I wonder, for those of us running under the belt-driven pump STC which also requires the nose bowl from an early 172 to be installed, if at some point in the future we ditch the pump and go the way of either electric or Venturi are we strictly required to change the nose bowl parts back to original 170 setup (i.e. return to pre-STC condition) or is there a method that allows us to keep the 172 parts installed?
1953 C170B - N170RP S/N 25865
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ghostflyer
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Re: Rapco Belt Driven Pump

Post by ghostflyer »

The way technology is racing away and having vacuum driven instruments will be of the past and that's including some electrical driven instruments . My venturies have worked very well but getting the vacuum instruments overhauled or purchased new is getting harder. So the answer is maybe a Garmin G5 or similar product . Its STC,d all legal and a very robust system plus upgradable for the future. To make my point even harder, when you go to Oshkosh or Sun and Fun how many instrument makers are there selling new design or upgraded vacuum instruments. I can hear the chorus now "what happens if I lose power or some thing electrical goes wrong ?" They [digitial instruments]have battery back ups. It was explained to me that the chances of that happening is the same as if you loose your generator and the aircraft battery goes flat on one of your flights now. Fitting the Garmin G5 is a no brainer. Just watch your clearance between the back of the instrument and the control yoke .
flyboy122
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Re: Rapco Belt Driven Pump

Post by flyboy122 »

rydfly wrote:Thanks for doing the research on these old vacuum pumps.

I wonder, for those of us running under the belt-driven pump STC which also requires the nose bowl from an early 172 to be installed, if at some point in the future we ditch the pump and go the way of either electric or Venturi are we strictly required to change the nose bowl parts back to original 170 setup (i.e. return to pre-STC condition) or is there a method that allows us to keep the 172 parts installed?
I think it would depend on how the STC is written and the drawings. If the drawings show the cowling and pump as separate installations, you may be able to get away with it. It's really hard to explain as there isn't some specific wording or such to look for, it's just in how it's interpreted. It's kind of the "you'll know it if you see it" thing.

DEM
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Bruce Fenstermacher
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Re: Rapco Belt Driven Pump

Post by Bruce Fenstermacher »

Changing the accessory case to the D model to get a vacuum pump has been done in the past under a one time approval. You would also have to use the angle starter and rewire for that. Good luck with getting that approval today.

You would not be converting your A to a D as it would then have the wrong 8 bolt crank to be a D. You might convert to a D but then get approval for the 8 bolt crank. There are those engines out there as well. And there is an STC to run the 8 bolt crank in a D. If you wanted to pursue it you would talk your IA into using Continentals SB to convert your engine by stamping the data plate. Then get permission to use the STC to keep the 8 bolt crank, can give you contact info. Of course you would also have to obtain a D accessory case, angle starter and vacuum pump and rewired and plumb. You would also need to buy the Associations STC to install the franken D model you created in your 170. And anyone who looks at the records for say annual or resale will find all the paperwork and data plate stamping pretty interesting.

Really, venturis don't look that bad do they?
CAUTION - My forum posts may be worth what you paid for them!

Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
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Lee
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Re: Rapco Belt Driven Pump

Post by Lee »

Update ... I decided to maintain the current installation and hope I have a vacuum pump that is still functional and will remain functional until I can go all electric. I like the Dynon D10A (AOA available option and I like the display better ... similar in some respects to the the Mad Dog I used to fly) The advantage the Garmin G5 has is direction indicator. The Garmin is apparently approved as a substitute for both attitude and direction. My understanding is that the Dynon, at this point is attitude only even though they too have an optional magnetometer which gives a dampened heading indication ... not sure how Garmin has approved substitute for DG heading and and Dynon does not. STC? Pricing appears to be comparable. Next year! :-) R/Lee (N1967C)
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GAHorn
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Re: Rapco Belt Driven Pump

Post by GAHorn »

I like Bruce's response. Venturiis have no moving parts, are already approved, and are original. (And I have two originals for sale cheap...heh-heh...)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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