Brock KB2 - McCullough or Rotax?

[WaspAir]

They have a reputation for quitting at inconvenient times ("Mac Attack"). They were designed for target drones, expected to be shot down, and not man-rated for routinely carrying humans to heights and back.

 

[GyroChuck]

I will add a Mac with electronic ignition and careful feeding of proper fuel (100 octane) and oil will be more reliable. There are a few people who have had good experiences with a Mac engine. But they are the exception who knew how to take care of the engine. Wasn't just luck.

Also consider where to get replacement parts and service on the engine. I have 3 Rotax repair stations within 90 minute drive of where I live.

 

[BrianInVa]

Also consider where to get replacement parts and service on the engine. I have 3 Rotax repair stations within 90 minute drive of where I live.

This is my primary concern.

 

[MikeBoyette]

Why are Macs so controversial. Seems folks either love them or hate them.

They are very unreliable. They were originally made for target drones so no need for durability or longevity. Made as light and powerful as possible. On many occasions the crank shaft was described as an undersized bent coat hanger.

 

[scottessex]

How much do you weigh? 180 or less?
You can use a 582 with a 2:00/1 gearbox ratio and a 54" prop and it will fly fine.
Look up Tim Chick's old Bensen we put a 503 with a short prop . it flew fine, then he sold it to Moe (also lightweight) in Wauchula, and he flew it for years just fine.

This is the easiest way to go without doing drop keel, taller mast, and everything that goes along with that conversion.
Of course it will not fly as fast as a long legged gyro with a large prop, but you will be able to keep the gyro you have.
That is why pilot weight is important.

 

[BrianInVa]

How much do you weigh?
You can use a 582 with a 2:00/1 gearbox ratio and a 54" prop and it will fly fine.
Look up Tim Chick's old Bensen we put a 503 with a short prop . it flew fine, then he sold it to Moe (also lightweight) in Wauchula, and he flew it for years just fine.

I’m losing weight but I’m 6’2” and 275 pounds. So some folks already advised me to go up to a 582 for the Brock.

 

[Sv.grainne]

You've picked up 2 older gyros in the last few days. Seems to me that pilot weight is going to be a big issue. Also, my concern is how/where are you going to have annuals done?

 

[BrianInVa]

You've picked up 2 older gyros in the last few days. Seems to me that pilot weight is going to be a big issue. Also, my concern is how/where are you going to have annuals done?

One gyro with one 503 engine but the option to trade that for a 582. Sorry for being repetitive and causing confusion with my enthusiasm.

Now I hope to use many of the controls from this Brock and a 582 motor to build a tractor style Little Wing Autogyro. I trust the LW design far more than the Brock KB2 to be quite honest.

The Brock has a tag on the vertical stabilizer saying 250lbs. I guess I hoped to stay in the part 103 category with it. But I’ll need to apply for an Experimental for the LW once it’s built.

 

[Doug Riley]

IIR, some Little Wings (maybe all of them?) used Teleflex cables in the control system. This avoids a collection of bellcranks, walking beams and the like, but limits how many parts from a Bensen style gyro can be adapted to the LW.

 

[Butch]

Why are Macs so controversial. Seems folks either love them or hate them.

I have had a 90 hp mac for 4 years now . I have never had a problem with it. I changed the ignition to CDI

 

[BrianInVa]

Hi Brian…..swing on by….. I believe Stephen Chadwell will be there and a few others. I’m there Saturday night and Sunday…. but we’re usually there, Saturdays and Sundays.

Sorry I missed the gang this weekend. I was headed over on Route 40 on Saturday with the Brock K2 and my water pump decided to depart this mortal coil. I was towed to Benson and had to stay at a hotel till Monday when the repair shop opened.

The seller included a rebuilt 503 with the Brock and I am trading it even up for a 582 on Monday. I’m going to look at an Affordaplane frame on Thursday. As I said in another thread, I’m seriously considering building a tractor style gyro out of the Brock frame and controls, the 582 and the affordaplane frame. I probably should just learn how to fly first lol!

Regardless I’ll bring it down to the Barnstormers at some point to chat with the gang there and see if they can talk me out of this harebrained A-Ffranken-gyro idea.

 

[BrianInVa]

I’m a big guy, 6’2”, 275 pounds. I have lost ten pounds this summer and plan to lose more. Regardless every gyro guru I’ve spoken with up till today said this Brock needed a 582 and big prop considering my size but should fly fine with one.

Today a gyro CFI told me I’m way too big for the Bensen/ Brock type gyros and that will eventually cause a crash.

Does anyone have any thoughts on this???

 

[Brent Drake]

I'd go with a Gyro Technic with a 912 on it at your weight.

 

[BrianInVa]

I'd go with a Gyro Technic with a 912 on it at your weight.

My financial status would never permit that.

So…how much weight do I need to lose to fly this Brock KB2? Would longer rotors help?

 

[Sv.grainne]

40 - 50 lbs would be my estimate.

 

[BrianInVa]

40 - 50 lbs would be my estimate.

My current goal is to get down to 240.

 

[Sv.grainne]

That's a good goal!

 

[BrianInVa]

Something I just now noticed. The original Brock Vin plate on the rudder says 250 pounds empty weight, 600 pounds max weight, with the original Bensen rotors.

That’s 75 pounds more than my current weight according to them. Some of that will be lost by updating from the Mac to the 582 and installing a tall tail, but I’m actually relieved.

I just thought it said 500 pounds max because I hadn’t looked at it closely enough before now.

Yes, my weight is still a problem, but I’m relieved to see this now.

 

[WaspAir]

That number was provided by an amateur builder. It is not an indication that it flies well at those weights, or was ever fully tested with that load. That value likely must also account for fuel.

 

[BrianInVa]

That number was provided by an amateur builder. It is not an indication that it flies well at those weights, or was ever fully tested with that load. That value likely must also account for fuel.

Ok thank you for that clarification. Wouldn’t the gross weight numbers provided by the amateur builder come from Brock’s build manual?