Bensen style

S

stolking1

Newbie
Joined
Jul 22, 2011
Messages
66
Location
Phoenix
I am a newbee again... sorta!

Years ago (30) I built a Bensen BM8 to spec. Shortly there after I changed to a seat tank and Alum wheels just for looks. It had a 72hp Mac.
Bill parsons told me he would guarantee the engine would quit when I needed it the most. That coupled with several friends getting hurt or worse I sold it.
Now I am reading that it may have been close to the correct CLT.
I want to get back into Gyro's and have Mac 90 just waiting if I go that route.
I need a lot of input on what to build or buy and if the BM8's are truly safe with the seat tank and alum wheels?
Also does the exhause change it back since going away from the steel tank and steel wheels was what made it safer? Help!

JD
 
HI JD

If you are going to use a Mac, you are more brave than me, but that doesn't take much. A Mac 90 is a power house for sure, and I will leave it at that. Now if you want to "cover your bet" I would make a drop keel version of the Bensen and FOR SURE PUT A TALL TAIL OR A "T" TAIL on it and you will be in pretty good shape design wise, because if you decide to go with a latter style engine with a re-drive on it all you will need to change is the motor mount and maybe cheek plates.

Tony
 
A Bensen B-8 with a seat tank and light aluminum wheels will pretty much be dead-on CLT. Mine is within 1/2" of CLT.

No drop keel necessary with a Mac and 52" prop. Order the t-tail plans from Ron Herron and you'll have a safe stable gyro.
 
A Bensen B-8 with a seat tank and light aluminum wheels will pretty much be dead-on CLT. Mine is within 1/2" of CLT.

No drop keel necessary with a Mac and 52" prop. Order the t-tail plans from Ron Herron and you'll have a safe stable gyro.
 
What about the electronic ignition? Where could I purchase one? Or should I stay with the Mag and have it redone by R & D?
 
Try Rick Whittridge

Advanced Rotor Designs
937-878-2598
________________

Probably at Oshkosh this week.
 
I echo what Mike said. Put a decent stab on the tail and you'll have a good machine. Good luck with your Mac.
 
JD, Do a search here on the forum under Advanced Rotor Designs & you should find all the info you are looking for on the Mac. I will be at Mentone with lots of Mac stuff if your coming this year. Here are some photos of my CDI. I will have a few with me if your interested? Note- Engine mount & fuel pump not included with the CDI kit. Fuel pumps are a option.
 

Attachments

  • ARD Bracket.jpg
    ARD Bracket.jpg
    136 KB · Views: 1
  • DSCF0918.jpg
    DSCF0918.jpg
    137.5 KB · Views: 1
  • DSCF0916.jpg
    DSCF0916.jpg
    138.3 KB · Views: 1
Rick,
Thanks for the info. Can you email me the cost at [email protected]. Also does the CDI adjust the timing for the lower RPM and if so does it smooth the engine at all?
I need to better understand the operation of it. Not asking for any trade secrets but just a general disc of the operation.
Thanks for all you help guys with the information.

JD
 
Jd...

Jd...

I have personally found the reliability of the Mac 90 engine to be somewhat lacking....
I came to this conclusion after 18 whole minuets of uninterrupted service before failure!
Buy a Rotax and enjoy flying.
Ben S
 
Don't get me started!!!!!!!!!!

Don't get me started!!!!!!!!!!

Don't get me started,,,,about Mac's n other engines!!!!!!
I personally know of rotax engines,Subaru's, and 912's that have quit for one reason or another, yes other engines last longer before some tear-down is required,,,,but like a Franklin engine,,,,,the Mac has to be tore down much sooner than others but I for one prefer a Mac,,,, price, availability, and shear power to weight and above all,,,,simplicity,,,,is some reasons why I fly a Mac!!!!!
 
When I built my Gyro 30 years ago I had the following done to the engine. Mac 72 HP. magnafluxed the crank, balanced the crank, rods, wrist pins and pistons.
Had the pistons also cam ground and coated. Had the Holley 1940 with the correct jet. The mag was sent to R & D to be rebuilt. The correct bearings were put into the engine. The fuel was mixed in a 5 gal can with a gal of avgas put in then the Kendal 2 stroke and shook. then the rest of the 4 gals put in and shook again. Then into the seat tank. I flew it 40 + hours and it never missed a beat. The time was set using an average of all 4 cylinders.
To start it I would pull it thru with my hand over the intake 2 times and then go hot and the next pull it never failed to start...
But Bill Parsons told me he would guarantee when I needed it the most it would quit... I figured he knew what he was talking about so I sold it..!
I still have regrets and that is why I am building another one..

JD
 
stolking1 said:
When I built my Gyro 30 years ago I had the following done to the engine. Mac 72 HP. magnafluxed the crank, balanced the crank, rods, wrist pins and pistons.
Had the pistons also cam ground and coated. Had the Holley 1940 with the correct jet. The mag was sent to R & D to be rebuilt. The correct bearings were put into the engine. The fuel was mixed in a 5 gal can with a gal of avgas put in then the Kendal 2 stroke and shook. then the rest of the 4 gals put in and shook again. Then into the seat tank. I flew it 40 + hours and it never missed a beat. The time was set using an average of all 4 cylinders.
To start it I would pull it thru with my hand over the intake 2 times and then go hot and the next pull it never failed to start...
But Bill Parsons told me he would guarantee when I needed it the most it would quit... I figured he knew what he was talking about so I sold it..!
I still have regrets and that is why I am building another one..

JD
Click to expand...

Good! Do it just like you discribed above.
The only additional suggestions is to cut relief in the case for the rear cylinder. It helps tp balance the breathing of that cylinder. I understand Rick W. does this.
If possible, cut the groove behind the front main bearing to accept the spiral lock ring, and put a clamping collar on the crank in front fo the main bearing. Don't be tempted to use a set screw, the clamping collar is available from some of the bearing suppliers. This will carry your prop thrust on the front main rather than passing it back thru the crank journals.
When properly set up and maintained, it will run a long time.
When using auto gas, I retarded the ignition timing a couple of degrees. Those things were designed to run on 140 / 145 octane purple gas!:eek:
 
I use "ONLY" 100LL!!!
 
I understand the part for locking the thrust bearing but I need more info on the Relief you speak of here. Does anyone have pictures of this? Rick can you explain it to me please...

JD


The only additional suggestions is to cut relief in the case for the rear cylinder. It helps tp balance the breathing of that cylinder. I understand Rick W. does this.
If possible, cut the groove behind the front main bearing to accept the spiral lock ring, and put a clamping collar on the crank in front fo the main bearing. Don't be tempted to use a set screw, the clamping collar is available from some of the bearing suppliers. This will carry your prop thrust on the front main rather than passing it back thru the crank journals.
When properly set up and maintained, it will run a long time.
When using auto gas, I retarded the ignition timing a couple of degrees. Those things were designed to run on 140 / 145 octane purple gas!
 
Rick,
Thanks for the photos. A picture is worth a thousand words.
So you are working all the ports to insure good and increased flow.
There is nothing extra you are doing beyond this the the rear cylinder?

Again thanks...

JD
 
You must log in or register to reply here.

Similar threads

G
Fuel tank leak
Replies
8
Views
696
Chook
C
B
Help with finishing a KB3 in Georgia
Replies
2
Views
301
Bobby Rickels
B
R
Dominator project,.rolling frame pod and rotor hub and bar.
Replies
3
Views
716
Aerofoam
Aerofoam
Aerofoam
Air Command rotor head rebuilding?
2
Replies
37
Views
2K
Aerofoam
Aerofoam
gyroplanes
Are these points for the MAC engine?
Replies
0
Views
202
gyroplanes
gyroplanes
Top