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-   -   RV-14 Engine choice (https://vansairforce.net/community/showthread.php?t=98748)

Av8rRob 07-29-2017 09:35 PM

Mt 3 blade
 
Since this thread is turning into a prop discussion, what are the thoughts about using a MT 3 bladed prop. I think I remember the weight is 55lbs so it is more inline with the Hartzell. That should help with cg issues. Besides the 12,500 price any other issues?

redbaron 07-29-2017 10:20 PM

Viking aircraft engines
 
Take a serious look At the new Viking engines they have been upgraded and include some with turbo charging.

czechsix 07-30-2017 10:53 AM

Quote:

Originally Posted by Av8rRob (Post 1191440)
Since this thread is turning into a prop discussion, what are the thoughts about using a MT 3 bladed prop. I think I remember the weight is 55lbs so it is more inline with the Hartzell. That should help with cg issues. Besides the 12,500 price any other issues?

My fault for getting the thread off topic, but since you asked....Vans did a bunch of comparative performance testing on various props over a decade ago and published results in the RVator. As I recall Hartzell blended airfoil and Whirlwind provided the best cruise performance and the MT was several knots slower. After that report very few people put MT props on their RVs....Way more cost for less performance doesn't sell too well. That said, it's possible MT has since developed a newer blade design better suited for the RV series, you'd have to research to find out. Also FWIW three blade props from any manufacturer tend to have reduced cruise performance compared to two blades (hence the old saying "two for the go, three for the show"). Three blades also make removal of the lower cowl more difficult and shipping the prop for repair or overhaul a lot more difficult & expensive. So...thats why you see so few 3-blade props on RVs.

RV6_flyer 07-30-2017 11:23 AM

Quote:

Originally Posted by redbaron (Post 1191449)
Take a serious look At the new Viking engines they have been upgraded and include some with turbo charging.

Not sure why anyone would not follow Van's Aircraft recommendation on engines for an aircraft as expensive as the RV-14(A) kit. They designed the aircraft around two engines. An overweight under powered Honda engine conversion is something that I would not walk away from, I would RUN as fast as I could to get away from it.

David Paule 07-30-2017 11:40 AM

Quote:

Originally Posted by czechsix (Post 1191403)
....Hartzell... ...transmits lots of vibration back into the airframe (typical of any metal prop)....

A good dynamic balance will fix that.

Dave

czechsix 07-30-2017 12:33 PM

Quote:

Originally Posted by David Paule (Post 1191514)
A good dynamic balance will fix that.

The Hartzell on my -8A was dynamically balanced, but the metal blades don't absorb the engine power pulses, so they get transmitted back into the airframe. Not as noticeable at higher RPMs as it is at lower RPMs and especially during shutdown. The first time I got in a friend's -7A with a Whirlwind prop, it felt more like a car when he started the engine. Much smoother...those carbon fiber blades absorb a lot more of the power pulses than metal.

If you were flying a turboprop, metal vs composite blades wouldn't make any difference as long as the prop is balanced, but not so on piston engines.

MED 07-30-2017 05:49 PM

I spoke with several people at Oshkosh about the differences between the Hartzel aluminum prop and the composite. A couple of discussions helped me to decide to spend the extra $ and buy the composite. Specifically, composite props are "smoother" with less vibration transmitted to the airframe and engine environment, leading to fewer engine baffle cracks, etc. The second advantage, according to Hartzel, is that the composite prop leading edge is nickel, which is much harder than aluminum, leading to a reduced chance of prop nicks. Plus, they said if a nick occurred, leading to a crack in the leading edge, it was a simple job to replace the leading edge. Hartzel said by replacing the leading edge at overhaul, you would essentially have new blades. Unfortunately, the difference in cost is non-trivial. :eek:

rwtalbot 07-30-2017 05:54 PM

Quote:

Originally Posted by MED (Post 1191592)
The second advantage, according to Hartzel, is that the composite prop leading edge is nickel, which is much harder than aluminum, leading to a reduced chance of prop nicks.

When you hit something soft it takes a dent. If you hit a harder material it cracks. That has been the experience on MT blades for years. Perhaps the Harzell doesn't suffer as much. If it were me I would call my local prop shop and ask their advice.

Bigortho 08-13-2017 05:46 PM

RV-14A with Superior XP-400
 
We're building our RV-14A at Synergy in Eugene, OR. This is a followup to my post in Jan 2017. Ultimately we purchased and built our XP-400 at the Superior's build facility in Dallas, TX in Feb 2017. My son and I assembled it in 2 ? days and it started right up in the test cell. We build our experimental planes for "educational & recreational" purposes - why shouldn't the same philosophy apply to our engines! After all, how better to understand, maintain & diagnose our engine than to have put it together ourselves.

This week we finally mounted it to our plane. The Superior A&P's said it was no more difficult than mounting the IO-390. Other than torquing the Dynafocal #1 Bolt adjacent to the #4 Cylinder Pushrod Tube, we had no difficulties. *We used a shaved down box wrench to slip into the narrow space between the pushrod tube and crank case. *I have subsequently learned that Lycoming has a special (expensive) tool just to tighten this nut.

We then fit the Hartzell Prop Governor and B & C Alternators (both 60 Amp Boss Mount belt driven primary & 40 amp B/U to the vacuum pump pad) with Vans supplied hardware without difficulty. *The fuel injector line to the #3 cylinder had to be bent slightly to accommodate the Prop Governor cable bracket (which the Lycoming 390 also requires be done).

The Vans Firewall Forward Kit supplied baffling fit the XP-400 with minimal trimming - which the Lycoming 390 also requires. *So, all-in-all, I?d say that installing the XP-400 is no more difficult than installing a Lycoming 390.

So, in my opinion, the advantages of the XP-400 over the Lycoming 390 are:

15 extra HP
Better Oil Path Flow with injectors to cool & lubricate the cylinders
P-Mag instead of Slick Magneto Ignition
Cold Air Induction
Choked Nitrided Cylinders to maintain compression
Horizontal,*Aluminum Sump that provides the extra space under the cowling to install Vetterman Exhaust with sound mufflers
The opportunity to build the engine at the Dallas facility.
Cheaper Price

The day after we uncrated our engine, a fellow RV-14A builder at Synergy used our crate to pack up his installed IO-390 and ship it back to Lycoming to have the Connecting Rod wrist pin bushings replaced as required by the new mandatory AD. As Synergy uses a different source for connecting rods & bushings - their engines are not subject to the recall.

A quote from my Superior build technician, Darrell Ingle, "we get our SL13923A bushings from a different vendor source than Lycoming so your connecting rods and bushings are good and don't fall under that Service Bulletin."

Tomcat RV4 08-13-2017 07:17 PM

I thought we are experimenters, made adaptors to mount 2.5 Subaru STOCK 165HP, wrx engine,to same o-320 engine mount, SDS Computer,to run ignition ,fuel injection, because RV 4, had to build modified cowl,any side by RV would be piece of cake ! Stock headers with,resonators from center pipe, made quieter than 172,,same awesome performance as
any RV 4,yet on car gas/achohol. A real hoot ! Also used stock suby fuel pumps in each tank! Had to plumb return lines for FI...Tom


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