BME 50 Prop Question
10-13-2005 | 01:40 PM
#1
BME 50 Prop Question
I'm getting a BME 50 and I'm wandering which prop to use. On their website, they have a BME 21x8, 22x8, MenzS 21x8, and Mejzlik 22x10 as the recommend props. I would really like to use a 22x8 MenzS and I've always heard that BME props tend to load the engine some. So, would I be ok using this prop here at 5000 ft. or will it load the engine down too much? I guess if this won't work, i'll just use a Mejzlik 22x8.
10-13-2005 | 02:35 PM
#2
RE: BME 50 Prop Question
All the guys at the arvada field over in Golden are using 22-8 on their BME50 engines. That field is at 5973' elevation.
Most are using a Menz Standard or a Menz Ultra.
Remember, the BME is a converted chainsaw engine. So, you want to let it spin up a bit. If you prop it for 6500RPM--your gonna hate it and end up cussing it. It's ported and timed to run up in the 10,000RPM range as a saw--but you can't and don't want to run it that high with a prop on it.
Prop it for 7000--7500RPM on the ground and run the high speed needle about 1/8 or 1/6 of a turn rich for about 5--8 gallons. Then lean it out to max and back off about 1/16th turn--maybe just a snootch more. Fly it.
Don't listen to all the local gas engine "experts" who are gonna tell you to run a 22-10 on it. It won't turn that much prop at this altitude.
Breaking it in with too much prop is NOT the right thing to do with a gas engine--or ANY engine. You want it to spin up into the higher RPM range and it needs to do that with a light load on it. If you break it in at 6300--6500RPM with a big prop---then it's always gonna be a dog and you'll always cuss it for not having any power. Overloading it with a big prop when it's still breaking in is just gonna make it HOT. Getting a new engine HOT is the worst thing you can do to it.
Keep it slightly rich and let it spin.
If you take my advice and break it in at higher RPM--then it'll loosen up and run like a raped ape for a VERY LONG time.
Most are using a Menz Standard or a Menz Ultra.
Remember, the BME is a converted chainsaw engine. So, you want to let it spin up a bit. If you prop it for 6500RPM--your gonna hate it and end up cussing it. It's ported and timed to run up in the 10,000RPM range as a saw--but you can't and don't want to run it that high with a prop on it.
Prop it for 7000--7500RPM on the ground and run the high speed needle about 1/8 or 1/6 of a turn rich for about 5--8 gallons. Then lean it out to max and back off about 1/16th turn--maybe just a snootch more. Fly it.
Don't listen to all the local gas engine "experts" who are gonna tell you to run a 22-10 on it. It won't turn that much prop at this altitude.
Breaking it in with too much prop is NOT the right thing to do with a gas engine--or ANY engine. You want it to spin up into the higher RPM range and it needs to do that with a light load on it. If you break it in at 6300--6500RPM with a big prop---then it's always gonna be a dog and you'll always cuss it for not having any power. Overloading it with a big prop when it's still breaking in is just gonna make it HOT. Getting a new engine HOT is the worst thing you can do to it.
Keep it slightly rich and let it spin.
If you take my advice and break it in at higher RPM--then it'll loosen up and run like a raped ape for a VERY LONG time.
10-13-2005 | 03:02 PM
#3
RE: BME 50 Prop Question
So, if I used a MenzS 22x8 for break in, I'd be doing the right thing? Like I said, i'm concerned about over propping it here at the higher elevation. But I would think a MenzS 22x8 would be less load than a BME 22x8.
10-13-2005 | 03:43 PM
#4
RE: BME 50 Prop Question
If you really want to make sure that your not overpropping it---but you want to get some thrust out of it-----use the Menz Ultra 22-8.
The Ultra is a narrow blade when compared to the S props from Menz.
I run a 22-10 Ultra on a 60cc engine. They put out PLENTY of thrust. Don't be afraid of the Ultra. And don't let some idiot at the local field tell you it won't pull or have any thrust because it's not an S blade or a Mejzlik or an APC or whatever.
Buy a Menz Ultra 22-8 and try it out. You will allow the engine to spin up and you'll get plenty of thrust for good flying. It's gonna spool up fast.
Thats what I'd really, honestly do with that engine. A Menz Ultra 22-8. If you can't get it up in the 7000RPM range--then drop to a 20-10. The smaller disk (diameter) will allow you to get the RPM up where you need them. I'll bet the 22-8 will do it--but if not, then drop to a 20-10 for a couple gallons. As the engine breaks in, it will get stronger and gain RPM. When it finally gets up to 7500RPM--then slap the next size bigger prop on it and slow it down to 7000RPM again.
It might work out like this:
20-10 for break in. Maybe 7000--7200RPM. Just guessing, but I'll bet I'm close.
Let it run like that for a few gallons. When it gets up to 7500RPM on the ground--switch to the Menz Ultra 22-8.
I'd just buy any ole' cheap 20-10 for break in. Buy one with a standard blade or a narrow blade. Don't slap a boat paddle on it with a blade that's 2" wide. Get a cheap Zinger 20-10 and run it for awhile. You won't have gobs of thrust--but it'll fly your plane just fine.
When the RPMs get up to 7500--then switch to the 22-8 Ultra and slow it back down a bit.
The Ultra is a narrow blade when compared to the S props from Menz.
I run a 22-10 Ultra on a 60cc engine. They put out PLENTY of thrust. Don't be afraid of the Ultra. And don't let some idiot at the local field tell you it won't pull or have any thrust because it's not an S blade or a Mejzlik or an APC or whatever.
Buy a Menz Ultra 22-8 and try it out. You will allow the engine to spin up and you'll get plenty of thrust for good flying. It's gonna spool up fast.
Thats what I'd really, honestly do with that engine. A Menz Ultra 22-8. If you can't get it up in the 7000RPM range--then drop to a 20-10. The smaller disk (diameter) will allow you to get the RPM up where you need them. I'll bet the 22-8 will do it--but if not, then drop to a 20-10 for a couple gallons. As the engine breaks in, it will get stronger and gain RPM. When it finally gets up to 7500RPM--then slap the next size bigger prop on it and slow it down to 7000RPM again.
It might work out like this:
20-10 for break in. Maybe 7000--7200RPM. Just guessing, but I'll bet I'm close.
Let it run like that for a few gallons. When it gets up to 7500RPM on the ground--switch to the Menz Ultra 22-8.
I'd just buy any ole' cheap 20-10 for break in. Buy one with a standard blade or a narrow blade. Don't slap a boat paddle on it with a blade that's 2" wide. Get a cheap Zinger 20-10 and run it for awhile. You won't have gobs of thrust--but it'll fly your plane just fine.
When the RPMs get up to 7500--then switch to the 22-8 Ultra and slow it back down a bit.
10-13-2005 | 04:04 PM
#5
RE: BME 50 Prop Question
Yeah, a norrow blade should work. The plane is going to weigh somewhere between 13.5-14 lbs. so I don't really need a bunch of thrust to move air. So, i'll order a Menz Ultra 22x8 and put the tach on it. If that doesn't work, I'll have a Pro Zinger 20x10 on hand and ready to go.
