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Wobble Pump

 
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norse



Joined: 19 Sep 2005
Posts: 12
Location: Irvine, CA

PostPosted: Mon Apr 17, 2006 8:03 pm    Post subject: Wobble Pump Reply with quote

The wobble pump introduced after the model 35 "C" was introduced is required for the E225 engine conversion. As such, what is involved in switching out the older (combination pump and fuel tank selector) configuration? What parts other than the wobble pump itself is required?
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Bryan Wells



Joined: 01 Sep 2005
Posts: 75
Location: Stephenville, TX

PostPosted: Tue Apr 18, 2006 4:53 pm    Post subject: RE: Wobble Pump Reply with quote

Hi Norse,
You are correct about the later style hand pump for the early model E225 installation. The differences being the fuel line attach mounting locations and the wobble pump housing is slightly different but the original could be modified. Plenty of early model 35's are out there with the E225 and still have the original wobble pump, but many have added the electric boost pump. My opinion is that all the early model Bonanza's should have the electric boost pump installed regardless of which wobble pump installed. If your engine driven pump fails, the hand driven pump is too much of a distraction and your arm will tire out before you can get to far. Imagine trying to hand pump the wobble pump, fly the airplane and hand crankdown the landing gear <G>. Unless you just want to go though the exercise, I would just make sure I had a good electric boost pump first.

Bryan
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norse



Joined: 19 Sep 2005
Posts: 12
Location: Irvine, CA

PostPosted: Wed Apr 19, 2006 7:57 pm    Post subject: Reply with quote

Hi Bryan,

I agree that an electrical back-up to the wobble (or combination hand pump and selector valve which I call the "plunger") is the way to go.

But, I want to be clear on replacing a "plunger" with a "wobble" installation. With the exception of 1) modifying the housing cover and, 2) re-routing the fuel lines, the "wobble" will be a form, fit, functional replacement? In other words, not other hardware is required to make the "wobble" installation. Is this correct?
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Bryan Wells



Joined: 01 Sep 2005
Posts: 75
Location: Stephenville, TX

PostPosted: Thu Apr 20, 2006 5:23 am    Post subject: RE: Wobble Pump Reply with quote

No, I can't say that to be true. They are basically the same pump except that the later style with handle lays horizontal and has a seperate selector valve. The earlier vertical pump of course has the selector valve and pump combined. Do you have both in hand? Do you have the illustrated parts manual diagram handy. I believe you will have to do a little more than just unbolt one and install the other, nothing seems just that easy. I would pull the cover off of both from two different airplanes and compare first. I've taken out and rebuilt the early vertical pumps and had the same idea to replace to a later side handle horizontal pump but deicded to just install a electric pump first and then worry about maybe changing the wobbles.
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norse



Joined: 19 Sep 2005
Posts: 12
Location: Irvine, CA

PostPosted: Thu Apr 20, 2006 5:18 pm    Post subject: Reply with quote

Brian,

Just received Beechcraft Installation Instructions for the Bonanza Fuel Unit, Part 35-924230-7 (wobble) from Raytheon Technical. This six page instruction refers to Kit 35-576 S issued on 8-25-51 and revised on 4-15-55 and 1-12-72. Bottom line: 1) rework bracket assembly (35-410146), 2) install the -6 and -8 reinforcements to the bracket assemblies. There other important checks and replacements to perform but, nothing more major than items 1) and 2). I have a copy of the instructions that I can fax to you if you want.

Norse
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Bryan Wells



Joined: 01 Sep 2005
Posts: 75
Location: Stephenville, TX

PostPosted: Thu Apr 20, 2006 5:26 pm    Post subject: wobble pump Reply with quote

Sure, I would like to post them on the web. if you have a scanner you can upload onto the web site too. Which ever is easiest for you.
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norse



Joined: 19 Sep 2005
Posts: 12
Location: Irvine, CA

PostPosted: Sun May 07, 2006 3:35 pm    Post subject: wobble waffle Reply with quote

Bryan,

Do you have further information on installing the Dukes electric fuel pump (boost pump) to a B35 with vertical hand pump? I wonder how an FAA inspector would view and approve a 337 for any engine conversion (from 185/205 to 225) lacking a wobble pump (as prescribed for conversions) but includes a Dukes electric? Any comments on this?

Norse
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Bryan Wells



Joined: 01 Sep 2005
Posts: 75
Location: Stephenville, TX

PostPosted: Sun May 07, 2006 4:30 pm    Post subject: wobble pump Reply with quote

Depends on the FFA inspector I suppose. A wobble pump can be either style, vertical with integral selector valve like the early type 35 thru B35's or later arm style like the C35 thru G35's had. A manual hand pump is not necessarily a bad thing, but in later year models, they went away and all we get is the electric pump/prime and engine driven. In the very rare case of having complete electric failure and a engine driven pump failure and we'd wish we had a hand pump. In any case, its the ability of the wobble pumps to keep up with the engine fuel consumption at full power, its either the hand pump or the person operating the hand pump. The maximum fuel burn rate of the E-series engines all being of the approximate 470 cubic inch range, will consume around 22 gph under full power. That is allot to ask for a hand pump to deliver. Your arm will tire very quickly if you have to rely on the hand pumps to deliver fuel. The later style wobble pump offers a little better performance due to a longer handle and maybe a bit more fuel delivery. But about all they are good for is to prime the engine for starting. I just don't have much data on anyone using the hand pumps to get them down safely. The hand pumps are required to be in the 35 thru G35 Bonanza's and it would be to much trouble to remove one all together and replace with a set up from a later style Bonanza, but it could be done I suppose. The only easy option is to add some of the electric pumps from existing STC's available. You might want to explore the STC listings for them and call around to find the best deal. I just don't know how critical it is to have the later style hand pump with the E225 engine or if it is considered legal to still have the early style hand pump with the E225 in the B35 or earlier. All I know is, I see allot of B35's and before with E225 engines and the original wobble pump, when I ask most all have added an electric pump. If you consider the hand pump as just a priming pump and the electric pump as the backup for the engine driven pump, then I think you have a workable solution. And some pilots even use the electric pump as the prime pump and never touch the wobble pump for priming. The acceptable engine replacement documentation was written over 50 years ago and might be written differently today is they took a look at it. If you want to or need to go by the letter today, then change out the wobble pump. As for installing a duke's electric pump, find a 337 or a STC that supports it and verify that your AP/IA and FAA office will approve the install and your in good shape.
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norse



Joined: 19 Sep 2005
Posts: 12
Location: Irvine, CA

PostPosted: Tue May 09, 2006 9:09 pm    Post subject: Reply with quote

Excellent comments. And, I agree that the main difference in the two styles of pumps is that wobble is easier to pump the fuel given it's cantilevered design. As for the fuel delivery rate per stoke of each type pump, I can't see any significant differences.

I will investigate the electric pump and cost with the understanding from others that the Dukes pump is fairly expensive. NOTE: It's my opinion that the risk of the engine driven fuel pump (Thompson or Romec) going bad is much less than your engine coughing out. Given the 250 hour inspections that the fuel pump must endure, it does not represent a high risk failure item.
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Bryan Wells



Joined: 01 Sep 2005
Posts: 75
Location: Stephenville, TX

PostPosted: Tue May 09, 2006 11:26 pm    Post subject: fuel pump issue Reply with quote

I actually do think the engine driven fuel pump is a very critical item and has proven with NTSB data that they do fail often. These pumps are getting older and if you break one apart, you can see why. The coupling that the pin joins is a critical area, most are getting oval shaped and don't allow the pin to stay aligned and will in short time fail. These failures are usually when someone has just torn one down for inspection. I haven't added them all up, but I would say more than a third of all fatal accidents in a early Bonanza is related to fuel issues, and allot are the pumps in recent years. For the Thompson, you just can't get any good new parts. I have contacted Romec, to start producing new pumps, they said they would consider it, but I doubt it will happen, they do still have all the engineering diagrams to do so. I suspect what may happen is to adapt a later model pump to these engines. So the problem with the Thompson pumps is the internal vane drive and coupling and pin setup. Most of the pumps today are worn. The pump aren't suppose to last for ever, but with now new parts availability, they are all destined to fail. Lost of Bonanza owners are no longer with us because of failed engine driven fuel pumps.
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norse



Joined: 19 Sep 2005
Posts: 12
Location: Irvine, CA

PostPosted: Wed May 10, 2006 8:02 pm    Post subject: Reply with quote

Hi Bryan,

I don't disagree with your comments but will add that fuel pump failures are due to owner neglect. They are not faulty or unreliable devices. My Thompson 1900 has been in continuous use, as best as the records bear out, since 1950. I have had to replace the rotor - a very expensive maintenance item - as all four holes were oblong. This repair accomplished as well as new seals and washers and screws, flow and pressure checks, etc., I've got every confidence this unit will continue to do it's job as will the generator, starter, mags, and wet vacuum if properly maintained.

Norse
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Bryan Wells



Joined: 01 Sep 2005
Posts: 75
Location: Stephenville, TX

PostPosted: Wed May 10, 2006 8:44 pm    Post subject: Thonpson pump Reply with quote

You keep your pump in better shape than most people. I was also thinking about Thunderbird, that the FAA did enforcement action on regarding faulty work on these pumps with bad parts used and caused some downed Bonanza's. The pumps just don't have much redundancy and I consider the electric pump a better back up than the wobble pump. I just consider NTSB data about the fuel related and fuel pump related accidents to be valuable consideration. These are all good discussion points and help bring awareness.
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