ken brock (infowanted]

diadave

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Aug 11, 2015
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leeds uk
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brock kb2
Hi everyone. This my first post on your great forum.I am wanting any build ,p ilot orany flight info on my KB2.It has the VWbeetle type aircooled engine with 1835cc capacity.thanks in anticipationof help in this matter. Asyou can pprobably tell I,m from the uk.but please:yo: don't hold this against me.::yo:::
 
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Doug Riley

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Dave: The KB-2 is essentially a 1969 Bensen B-8M, with Ken Brock's special accessories added.

I flew an 1835 cc B-8M/VW of that vintage. What would you like to know?

Certainly get training that focuses on the faster reaction time and neutral pitch stability of a single-place gyro with a small, fast rotor and no effective horizontal stabilizer . Magnis and the like are much more leisurely in their reactions.

The 1835 cc is not a powerhouse. You must have a good grasp of power management and the concepts of power- and drag-curves.

VW's vary greatly in their reliability. Mine was less reliable than a 2-stroke. A good conversion involves generous oil cooling, reinforcement of the crankshaft and internal balancing.
 

diadave

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leeds uk
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brock kb2
Many thanks doug.

Many thanks doug.

Hi doug. Many thanks for that invaluable info. I think I was already going to fit an norizontal stab. As for the engine concerns, the engine was purchased new from ken brock when the craft was first built. Also the builder was a rolls Royce engine engineer, who was working for Boeing at the time of first use. I hope he knew his onions so to speak. As for training, your concerns have been taken on board and, I agree. again many thanks for the info.:
 
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diadave

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leeds uk
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brock kb2
Many thanks doug.

Many thanks doug.

Hi doug. Many thanks for that invaluable info. I think I was already going to fit an norizontal stab. As for the engine concerns, the engine was purchased new from ken brock when the craft was first built. Also the builder was a rolls Royce engine engineer, who was working for Boeing at the time of first use. I hope he knew his onions so to speak. As for training, your concerns have been taken on board and, I agree. again many thanks for the info.:I was really hoping someone could come up with a brock pilot or performance mauual for this machine so I could save money with getting a flight log built up for this machine.:humble:
 
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Doug Riley

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IIR, Ken obtained his VW conversions from one of the "usual suspects." I imagine his supplier was either Great Plains or HAPI.

Revmaster made (and makes) the most completely remanufactured aircraft version of the VW that I know of. They always were really expensive, however, so I doubt that Ken used them. Your builder may have bought directly from them, I suppose. Some pictures would help.
 

diadave

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leeds uk
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brock kb2
Thanks again Doug and Mike. What would a newbie do without the knowledge that is out there.I think we would (,crash and burn.)possibly literally.I am away from home at the mo, so don't have the info on the engine here. I will post details and possibly pictures (if I can fathom how.) on my return .The original owner wrote an article about the build for the ROLLS ROYCE magazine in 1983 and in it he describes the engine and its internal parts. Anyway thanks once more.
 

diadave

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leeds uk
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brock kb2
Hi again doug.

Hi again doug.

Your assumptions were correct about the engines pedigree .The crankcase is marked (made in brazil).so the engine is indeed a remanufactured unit.On returning home I checked the artidle and found mention of only a modified crank, ie prop flange and an oil cooler which of course all aircooled vw have anyway. The author then mentions amodified oil pressure sender and oil temperature which he fitted to the sump. Thanks again all you gyronuts out there. Any further help you think I might need will be gratefully appreciated.:
 

Steve_UK

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I'm not a pilot but have been lucky enough to fly in Mi-24 Hind, Mi-2, Mi-17, Lynx HAS3, Gliders, GA
Hi Dave,

Are you planning to fly this machine in the UK ?

If so you will need to talk with the LAA.

Regards
 

Doug Riley

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Dave: Prop flanges come in different flavo(u)rs.

If the prop is on the oil-pump end of the crank (as is usual except in the old Bensen/Mekker conversion), then it's attached where the fan pulley would go on the car. This crank journal, and its associated bearing (#4) are FAR too small and flimsy in their stock configuration to support a prop.

In the 70's, we had several incidents with gyros that used the stock #4 bearing and journal, in which the journal broke off the crank. There's nothing to hold it on at that point, so the bit of journal, and the prop attached to it, would depart the aircraft. It's a miracle if either the pilot or someone on the ground doesn't get killed in such an incidents.

Great Plains, Revmaster and (I think) HAPI all worked out crank and case modifications to prevent this catastrophe. The best fix is to machine a long taper on the crank, starting at the very end of the crank and proceeding right past the #4 and #3 journals. A flange with a long neck is then fitted over this taper. The outside surface of the neck, polished and perhaps case-hardened, becomes a combined #3 and #4 journal. The case is line-bored and a long, oil-fed sleeve bearing, with oil seal, is fitted in place of the small #4 and #3 crank bearings. The neck of the prop flange turns in this bearing. This is Revmaster's approach. I'm less familiar with the others.

Less elegant fixes may involve nothing more than drilling the original fan-pulley retention bolt hole deeper into the crank and fitting a longer bolt. This retains the whole mess on the remainder of the crank when the journal breaks. Great.

Bensen and Mekker used the large (clutch) end of the crank to mount the prop flange. They placed a bearing outside the crankcase, in the machined recess (90 mm dia.?) that holds the clutch-end oil seal. The prop flange was machined to fit the inner race of this bearing. I copied this arrangement on my last VW -- but the setup is quite unusual.

I suggest that you make certain that the flange setup on your engine is a safe and sound one. This is a life-and-death matter.
 

diadave

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leeds uk
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brock kb2
A very frightened gyronut.

A very frightened gyronut.

When am I going to thank you enough. What you say is t.rully frighteeningI thought iknew a small amount of the aircooled enginr but. I .know nothing of this.I can recognize the difference between each end of the crank.but I assumed, possibly wrongly .that an aircraft engineer would know his onions.Anyway I will certainly get this checked out before any serious attempts at flight.Could I pose another question for anyone Where apart from the rotor bolt should suspend the aircraft for a hang test. Talk about ignorance is bliss. I am :in your (everyones) hands . .
 
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diadave

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leeds uk
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brock kb2
Hi steve .I am checking the feasibility of the machine as a flying proposition before any contact about registration with the LAA or anything else for that matter.
 
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SandL

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Aug 27, 2011
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Royal Wootton Bassett... UK
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Bensen Merlin dragon wings Rotax 532
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400hrs (4,000 instructional launches) gliding, 200 fixed wing, 100 gyro
It is up to you but may I suggest that you look at the situation in the UK, the laws and rules are very, very different in other countries.
Unless you plan to take the machine abroad, much of your time and effort could be wasted unless you make a break through with the LAA, if you talk with Tom the BRA single seat representitave about his camble cricket (normally an approved type), he has been waiting and trying to get approval for over 3 years. one situation arrose where the CAA had to test fly it but the CAA had no test pilot. so everything stopped ... crazy I know, but true. in summary you need to talk with knowlagable people here in the UK
 

defiantone

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Apr 7, 2012
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Norfork AR
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Bensen B8M
A new twist on the old VW

A new twist on the old VW

Dave: Prop flanges come in different flavo(u)rs.

If the prop is on the oil-pump end of the crank (as is usual except in the old Bensen/Mekker conversion), then it's attached where the fan pulley would go on the car. This crank journal, and its associated bearing (#4) are FAR too small and flimsy in their stock configuration to support a prop.

In the 70's, we had several incidents with gyros that used the stock #4 bearing and journal, in which the journal broke off the crank. There's nothing to hold it on at that point, so the bit of journal, and the prop attached to it, would depart the aircraft. It's a miracle if either the pilot or someone on the ground doesn't get killed in such an incidents.

Great Plains, Revmaster and (I think) HAPI all worked out crank and case modifications to prevent this catastrophe. The best fix is to machine a long taper on the crank, starting at the very end of the crank and proceeding right past the #4 and #3 journals. A flange with a long neck is then fitted over this taper. The outside surface of the neck, polished and perhaps case-hardened, becomes a combined #3 and #4 journal. The case is line-bored and a long, oil-fed sleeve bearing, with oil seal, is fitted in place of the small #4 and #3 crank bearings. The neck of the prop flange turns in this bearing. This is Revmaster's approach. I'm less familiar with the others.

Less elegant fixes may involve nothing more than drilling the original fan-pulley retention bolt hole deeper into the crank and fitting a longer bolt. This retains the whole mess on the remainder of the crank when the journal breaks. Great.

Bensen and Mekker used the large (clutch) end of the crank to mount the prop flange. They placed a bearing outside the crankcase, in the machined recess (90 mm dia.?) that holds the clutch-end oil seal. The prop flange was machined to fit the inner race of this bearing. I copied this arrangement on my last VW -- but the setup is quite unusual.

I suggest that you make certain that the flange setup on your engine is a safe and sound one. This is a life-and-death matter.
Just thinking out loud here.
What if a person was to mount a flat plate on the clutch end of the VW engine
using the 4 bolt holes originally used to bolt up to the trans and use it as a mounting plate for a PSRU or perhaps the back plate of the PSRU itself and perhaps a outboard bearing to help support the crank?
Any thoughts on this guys?
 

Doug Riley

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6,386
It's been done, although actual examples are very rare. Obviously such a setup will add considerable weight.

Revmaster's strategy since the early 70's has been to boost displacement to the absolute extreme by boring and stroking, add a custom cam, increase breathing with custom heads but then redline the engine at under 3,000 RPM. Somewhat the same thing as using a smaller displacement, revving it faster and then employing the PSRU.

What you would want to avoid IMHO is hotrodding the engine via boring and stroking AND revving it fast. The Rotax 900's are designed to turn at 5800 RPM and to extract 100 hp or more from 1200 cc; the VW most certainly is not. Stroking the VW makes this even more true.

IIR, the certified Limbach-VW conversion was only 1700 cc, suggesting a slight bore-out and nothing more.

Remember that the basic VW infrastructure was designed to make just 40 hp using 1200 cc at 4,000 RPM -- and even that for brief periods only. In my experience, running even an 1835 cc VW (big bore; stock stroke) with otherwise stock parts at 4,000 RPM will fry the engine during an ordinary full-power climbout.* More must be done, and RPM limited, to assure reasonable reliability.
____________________
* Yeah, I did it. About 4 times, actually. Landed in many interesting locales, including the grounds of a maximum-security prison.
 

diadave

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Aug 11, 2015
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leeds uk
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brock kb2
Hi doug .thanks again for the info. I ve one hell of a lot of stuff to check before I can get anywhere. Just to add to it all Would adding a horiz. stab .of the (little wing) type of mod help stabilityand, is it true ,what ive read somewhere , that the KB2 is near C.L.T. anyway
 

diadave

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leeds uk
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brock kb2
Hi doug thanks again.

Hi doug thanks again.

Thanks again doug. Ive one hell off a lot of stuff to check before I can get anywhere near a flight. Ive read somewhere the KB2 is nearly CLT . Is this true



















































































































































Hi doug many thanks for yet more info.Ive one hell of a lot of stuff to check before I get anywhere near flight ready.One more thing id like toask. Is the KB2 near CLT as ive read.also (sorry that's two things) would the fitting of ahoriz stab as fitted to the bensen by the LITTLE WING company make thjs so.
 
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diadave

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Aug 11, 2015
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leeds uk
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brock kb2
Hi again steve thanks for the link to the photo of the kb2 . Id already seen this photo. this was the pic that had me chasing this machine in the first instance. I KNEW IT WAS CAA APPROVED TYPEand also some improvement on the bensen.
 

Doug Riley

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Messages
6,386
Dave: A McCulloch-powered KB-2 is essentially CLT. It is better than a Bensen in this respect because the fuel is mounted higher (in a seat tank) and Ken's wheel set is lighter than Bensen's.

I don't know if the VW version follows suit. The CG of a VW engine can end up below the level of the crankshaft (where the prop's center is), owing to the location of the oil sump, carb(s), magneto, etc. Some people have used larger diameter props in VW's, following the Revmaster philosophy that I mentioned earlier. This tends to place the prop thrustline above the CG of the aircraft overall. The only way to know for sure is perform a double hang test or other physical test for CG location vis-à-vis the centre of the prop disk.

A H-stab can perform as many as four different aerodynamic functions. It can compensate for a modest amount of HTL, as you suggest (a pitch-axis trimming function). It also can supply the airframe with positive angle-of attack static stability. It can enhance pitch-axis dynamic stability (pitch damping; preventing PIO). It can provide roll-axis trim (opposing prop torque).

If you have CLT, you don't need the pitch-axis trim function, but you still need the other three functions. Unfortunately, a H-stab mounted on the keel under the prop will not perform any of these functions to a noticeable extent. Any H-stab mounted on the vertical fin, high enough to lie within the propwash, will work much better. The fastest propwash is located at about 2/3 of the prop's radius out from the centre.

There's no appreciable propwash in the very centre of the prop disk; this "dead spot" varies in diameter, up to a foot or more, depending on the prop's design and on what structures are upstream of the prop disk.
 
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