stunthanger.com
Engine basics => Engine set up tips => Topic started by: Dane Martin on November 25, 2015, 09:02:36 PM
-
Ok, i did the search thing, and im confident enough in the prop size. Randy Smith has been helping me via email in the pipe and header.
So my question is... Is it a bad idea to use a xoar or mejzlik prop? The props that everyone mentions sound great, but i don't know where to get them. I'm shooting for competing in advanced this season, so i probably couldn't tell the difference in prop types anyway. And i like wood props, is that a good idea to use a quality wood prop?
-
Looks like I'm just dumb. Randy lists props on his website. Sorry guys.
-
Randy has CF props again? Bolly quit and then Mejzlik quit making F2B sizes. I haven't heard about any others, except Brian Eather, and Alan & Chris in BC. I got a couple of B.E. props late this year. Wishing I could afford to buy more, but mostly need a longer LG. Don't cut the prop clearance too short!
I sent you a PM with offer of some useful info. Are you going to run a pipe or muffler? Pipe, I hope. A little fiddling to get it working, but otherwise very reliable and no-fuss, from my 4+ years with them. y1 Steve
-
Ok, i did the search thing, and im confident enough in the prop size. Randy Smith has been helping me via email in the pipe and header.
So my question is... Is it a bad idea to use a xoar or mejzlik prop? The props that everyone mentions sound great, but i don't know where to get them. I'm shooting for competing in advanced this season, so i probably couldn't tell the difference in prop types anyway. And i like wood props, is that a good idea to use a quality wood prop?
I am pretty sure you would be able to tell! Presuming you have the same setup I run, you want a 12.5" 3-blade, and then adjust the pitch to get about 5.3 second laps with a launch RPM of about 10,000. It should 4-stroke throughout the flight under normal circumstances. For me, that's 3.75".
Brett
-
Ok,, cool guys. So the airplane is a kit built strega. My friend gave it to me. It's a great build, but a little heavy. I don't mean that as rude. Just compared to others, it's a little portly. I'll get the AUW when i find my scale.
Brett, you're probably right. I'm sure i could tell, so i guess my question is, can i get "cheaper" props to experiment on pitch because of my overweight plane? Or go with the three blade 4 and 5 pitch and try two?
I have watched this plane fly by someone who competes in advanced, with a ro-jett 65. So i know it's fully capable
-
Oh, and Steve. Yes a pipe. Randy is hooking it up! Told me what i need and he's got it in stock.
-
Brett, you're probably right. I'm sure i could tell, so i guess my question is, can i get "cheaper" props to experiment on pitch because of my overweight plane? Or go with the three blade 4 and 5 pitch and try two?
You get one CF prop, and you repitch it. At least -- that's the story I keep hearing. Basically, you get epoxy hot enough and it'll take a set. So heat, fondle, let cool, check pitch, repeat.
You'll want a fancy pitch gauge.
-
Hi Dane ,
What I recommend is set yours up as close to Brett's as you are able , his seem to work as well as any I've seen. I'd say that plane will put quite a demand on the engine . Good luck locating the proper propeller.
John L.
-
Eliminator Props in the Vendor's section sells copies of the Bolly 12 and 13" 4.24 pitch CF props. That would be a good place to start. 8)
-
Eliminator Props in the Vendor's section sells copies of the Bolly 12 and 13" 4.24 pitch CF props. That would be a good place to start. 8)
Lol, i just emailed Steve H last night, "why didn't i think of that?". My last batch of 1/2A speed props came from Steve Wilk. Thanks for the reply
-
Hi Dane ,
What I recommend is set yours up as close to Brett's as you are able , his seem to work as well as any I've seen. I'd say that plane will put quite a demand on the engine . Good luck locating the proper propeller.
John L.
Thanks John. Steve H emailed me the articles last night. Also, i checked out the post from Brett's nats set up. I'll just be copying that.... Thanks Brett!
-
Thanks John. Steve H emailed me the articles last night. Also, i checked out the post from Brett's nats set up. I'll just be copying that.... Thanks Brett!
Note that I have used a late Randy/Billy pipe on mine from the start, just like on my PA. Get the current model closest to the 51-60 "Slimline" pipe. Randy knows which one I am talking about.
Brett
-
Thanks Brett, and everyone for your responses. When i get the new pipe and header, I'll update you guys on my progress.
Tim, why didn't i think of that? Lol. Thanks!
-
Just as an update, i got the pipe and header. I'll take the header into the shop tomorrow. I'll need to modify it slightly. The engine is rectangular in the mount area, this header is a diamond. I'll just square it off a little. I'll do it there in case i go too far and need to tig weld the joint again. I believe there's plenty of room to take off material.
Anyway, i want to get on this thing and get it in the air. It's actually really nice weather here.
-
Ok, opportunity for solution number 1:
The header is actually a significant difference in size. I would need to machine off a lot of material, and weld the left over gaps. Or, easier option is to make an aluminum spacer plate. Are there any engineering or metallurgical oppositions to a spacer plate?
-
Ok, opportunity for solution number 1:
The header is actually a significant difference in size. I would need to machine off a lot of material, and weld the left over gaps. Or, easier option is to make an aluminum spacer plate. Are there any engineering or metallurgical oppositions to a spacer plate?
Dane The ones I have seen came with spacer plates, that is why I told you the short 1/2 inch bolts would not work
Randy
-
Oh, great. I guess i know see exactly what you're talking about. Then this is a very easy fix. I'll make a 3/16 spacer to clear the fins. That will be solved tomorrow. Thanks again Randy. This is going to be great
-
Oh, great. I guess i know see exactly what you're talking about. Then this is a very easy fix. I'll make a 3/16 spacer to clear the fins. That will be solved tomorrow. Thanks again Randy. This is going to be great
Note that the screws are 5-40's, not 4-40's. 4-40's will thread in OK but strip out when you try to tighten it.
The stub exhaust normally comes with it. Its 1/4" thick, about .518 x 1.21. Flatten and clean both mating surface, flatten and clean the facing part of the header, and clean the mating face on the engine. Then assemble it with Permatex "Ultra Copper" silicone (or the similar red high-temp silicone from 3M) and *nothing else*. DO NOT, repeat, DO NOT, use any separate gasket material of any type.
Use a spigot in the #5 venturi, carefully counterboring the dribble hole for the head of the smallest SIG eyelet (1/16 OD of the barrel of the eyelet). Push it in until it sticks out about .025-.032" from the surface. Use a panty hose diffuser on the inlet.
Brett
-
Dane The ones I have seen came with spacer plates, that is why I told you the short 1/2 inch bolts would not work
Randy - people keep asking me which pipe to use, but I don't know your part number/name/SKU for the correct version. The one they want is the nearest equivalent to the old Billy 51-60 "slimline" pipe that was 1.4" in diameter. What do you call that one?
It also needs the large exhaust outlet and the very largest ID DuBro stinger. They made a thin-wall version, that's the one I use. The black Hattori one also works. The large diameter outlet is critical. Even the big ones need to be cut off as short possible or it has drastic effects on the responsiveness.
Brett
-
Note that the screws are 5-40's, not 4-40's. 4-40's will thread in OK but strip out when you try to tighten it.
The stub exhaust normally comes with it. Its 1/4" thick, about .518 x 1.21. Flatten and clean both mating surface, flatten and clean the facing part of the header, and clean the mating face on the engine. Then assemble it with Permatex "Ultra Copper" silicone (or the similar red high-temp silicone from 3M) and *nothing else*. DO NOT, repeat, DO NOT, use any separate gasket material of any type.
Use a spigot in the #5 venturi, carefully counterboring the dribble hole for the head of the smallest SIG eyelet (1/16 OD of the barrel of the eyelet). Push it in until it sticks out about .025-.032" from the surface. Use a panty hose diffuser on the inlet.
Brett
Thanks for the info Brett. Thanks especially for the measurements. That's pretty easy to copy. I'll check what's on the spigot situation. Rumor has it, this engine was flown in the nats already. It might have a good set up. I bought it sans header and prop nut
-
Thanks for the info Brett. Thanks especially for the measurements. That's pretty easy to copy. I'll check what's on the spigot situation. Rumor has it, this engine was flown in the nats already. It might have a good set up. I bought it sans header and prop nut
Where'd you get it? That will tell me something about how it was being run before. PM if shy...
Check the venturi diameter and the presence/absence of the spigot, if no spigot, check that it has the 1/16" "dribble hole" rather than the .100 dribble hole. If the .1000, you can either fill it the way I showed in the old SSW post "cheater venturis...", or, better, get some new replacements with the 1/16" hole, and the "long" version rather than the "short" version. You can tolerate a pretty big venturi (although not nearly as large as were supplied with the GMA engine). But you may not be able to tolerate carrying enough fuel for, say, a #3 spigot. With a #5 anticipate about 6.5-6.6 ounces of 10% Powermaster "Air". If it is way lower (under 6) or way higher (7+), then something else interesting it going on.
Brett
-
Ok, so with a little luck, i got the spacer made. I was have mucho problems with my "mill" set up. The chuck kept falling off everytime i advanced the table forward! Whatever, i got it. I'm measuring a 5-40 × 7/8 exhaust bolt. Does that sound about right?
Brett, did i pm you? My phone sometimes skips the send portion of pm's
-
Ok, so with a little luck, i got the spacer made. I was have mucho problems with my "mill" set up. The chuck kept falling off everytime i advanced the table forward! Whatever, i got it. I'm measuring a 5-40 × 7/8 exhaust bolt. Does that sound about right?
Brett, did i pm you? My phone sometimes skips the send portion of pm's
Yes, I got it, but I haven't responded yet. I will check the header screws when I get a chance.
Brett
-
Ok, so with a little luck, i got the spacer made. I was have mucho problems with my "mill" set up. The chuck kept falling off everytime i advanced the table forward! Whatever, i got it. I'm measuring a 5-40 × 7/8 exhaust bolt. Does that sound about right?
Brett, did i pm you? My phone sometimes skips the send portion of pm's
Dane
just screw in a 540 to both holes in the case, see how far it goes in, take that measurement, add the thickness of the spacer and header block, the subtract 1/16 inch
you may need to trim a 1 inch bolt, or maybe not??
Randy
-
Thanks guys. I gotta order some bolts from like jl fasteners or something online. I don't have anything 5-40. I'll call the pres and tres of our club too. Maybe they got some laying around
Edit, just found out 5-40 bolts are very common in rc cars. Team associated especially. So hobby people has plenty. This is working out pretty easy
-
Why don't you call Dub Jett and get the right part and the right screws?
Just asking,
Tim
-
Why don't you call Dub Jett and get the right part and the right screws?
Just asking,
Tim
Tried that first. He seems to be a busy man. The spacer was pretty easy to make. Just annoying about the shop equipment
-
Is there an RPM i should be shooting for on the ground? Or is it an experiment with your set up kinda situation?
-
Ok, without the pipe, i was at 5.7 sec. I just timed it now for this first flight, and i was at 4.6 sec. So.... Not correct. But, the control system felt good. Obviously too responsive because I'm flying too fast. I know that it was a lean run... Not dangerously lean, just not correct
I have a cut down rev up. Was a 14, cut down to 13 with 5 pitch. I think Pat Johnston was gonna send me some props to test.
-
I don't have a RO-Jett .61, but I'd suggest setting the pipe length at whatever Randy's chart suggests for the exhaust timing it has...which I believe is up around 145*. Then, I'd borrow a CF prop or two from your locals and start launching at 10k to 10.5k. Using a prop you can't replace or isn't potentially the best prop for the combo isn't very productive, IMO.
Always get a reading on launch rpm every flight, so you know where to go from there. Be sure the engine is fully warmed up, because if it isn't, you don't really have a baseline. The engine will lean out as it heats up...about the time you get the handle strapped on. Don't run the pipe shorter than suggested...tends to burn down the engine, I think. I've heard PW say that a couple times, not speaking to me, however. Brian Eather makes really nice stunt props, and is pretty quick to get them to your door.
Email Brett if you need good prop advise. I would guess wrong, no doubt, but I've had very good results on the .46VF and PA .51 with the 12 x 3.75 undercambered 3 bladers (full 12" for the .51, 11.5" for the VF), so I'd probably try a 13" version and pitch it to 4" and maybe pitch up the last 2" to 4.5" or so. My experience indicates that the U/C props work better on overweight models...or maybe for overweight pilots? YMMV~ y1 Steve
-
Is there an RPM i should be shooting for on the ground? Or is it an experiment with your set up kinda situation?
Yes. The setup information will yield a desired launch RPM of about 10000-10100, in room-temperature air. Adjust the pitch and diameter to get the desired in-flight speed with that as a starting RPM.
I would expect 5" of pitch to be way too much. I run a 12.5-3.75 3-blade. The engine should run in a 4-stroke throughout the flight, or at most breaking into a 2 at the last few corners of the square 8.
Brett
-
Ok, i was lean, and it broke early in every maneuver. I really am taking this advice and applying it. I don't have the correct props, i just wanted to fly today. I'm gonna fly again in the morning. I'll change the prop and tach it before flight.
Steve, you are spot on about inquiring on pipe length. Randy and i had many conversations about that stuff. I started at 18.75 inches length
-
HI Dane
18.75 would be a closer place to start
Randy
-
Whoops, just caught that. Typo.
Thanks Randy
According to the charts, i would be in the 18.5 - 19.5 range, right?
-
Whoops, just caught that. Typo.
Thanks Randy
According to the charts, i would be in the 18.5 - 19.5 range, right?
yes ;D
-
Please set it up per this post:
http://www.clstunt.com/htdocs/dc/dcboard.php?az=show_topic&forum=103&topic_id=232053&mesg_id=232053
with the suggestions above. This is not an experiment or a new development, this setup is far and away the best stunt engine I have ever run or tried and has proven absolutely bulletproof over the last 13 years or so. The only issue is to get a prop that works with this system, but given the desired 10,000 rpm launch revs, the fact that it runs in a 4 stroke all the time, and has to fly at 5.25-5.4 laps, that should narrow it down to ONLY the prop. 5" appears to be *far* too much pitch. I am running 3.75" and the same system will work with 3.6 to 4.2 depending on the air density. 3.75 to 3.9 is the middle of the range. The second airplane flew better with 3.9, the current airplane does better with 3.75, even on hot days in Muncie.
The pipe length should be 17.5".
Brett
-
10-4. Will comply
Steve, you told me at one point who to contact for a new pitch gauge, but i forgot... Help me out again?
That's the only hold up i have on prop issues now. I don't fly with any one with props i can experiment with. I'm kinda solo in this endeavor, so bear with my learning curve guys..
Thanks!
-
Hi Dane
to follow Brett's suggestion, you will need to get the same Eather props, or clones, or it will not work, if you run more pitch as you stated you will need to run a longer pipe length, as I suggested, if not it will not be running and getting the pipe benefits, so first thing is you should try to get props, and a pitch gauge, I hope you have someone close who can help with the pitching of the props
let me know if you need help with anything
Randy
-
Hi Dane
to follow Brett's suggestion, you will need to get the same Eather props, or clones, or it will not work, i
It will work with other props. What you need to find a prop with similar load characteristics that provides the necessary speed, which is why you start with a known proven system and adjust the prop around it, not go off on a tangent with speculative systems.
Brett
-
It will work with other props. What you need to find a prop with similar load characteristics that provides the necessary speed, which is why you start with a known proven system and adjust the prop around it, not go off on a tangent with speculative systems.
Brett
to follow Brett's suggestion, you will need to get the same Eather props, or clones, "
hence the reason, i wrote the above in my post , he will need props that he can work pitch on, that are very similar to the ones you use
-
Ok, let me ask this dumb question... Sorry in advance. I'm measuring the pipe length from the glow plug to the first baffle. If anyone can see this black sharpie mark, i just want to verify that I'm measuring correctly. It's the part right at where the taper ends and the straight tube begins, right?
-
The yellow mark is the first baffle measure from there to the glow plug
Randy
-
Oh! I'm pretty sure you already told me that in an email when you mailed me the pipe. Sorry, but thanks again!
-
Ok, i got the pipe length set to 17.5". I read through Brett's article. I believe I'm set up the same. As long as i can prop it to get the same load and speed i should be done ! I'm heading out to the field now. I have my tach with me this time!
-
Ok. I already know I'm doing this wrong. But in the spirit of changing only one thing at a time to prove the necessity for change.... I changed the pipe length to 17.5 and tached it today to 10,050. Much too fast lap times. I timed it with my phone, so I'm not sure how accurate i was, however it was 4.5ish.
So... I'm still at the fact that i have the wrong prop. I knew that before this, but it was worth a shot just to see if it could be a little better.
The worse part of all this is knowing enough to know what i need, but not understanding or having the resources to get there. Doing this alone is really difficult! I don't see finding a prop, a pitch gauge and setting this all up before the Palmer at Whittier this month.
-
what pitch are you using now? try one with about 1/2 pitch less.
Also are you in a 4 cycle at that speed? or a 2 cycle?
You should try the setup launching the plane in the fastest 4 cycle it will run in on the ground, this should be a solid 4 in the air, check laptimes then
Randy
-
Thanks Randy. Like i said, i know I'm wrong on the prop. It was running in a pretty fast 4. I'm still running a 5 pitch. It's pretty much impossible to get my hands on a prop around here. I'm going to order the bolly repro from Steve Wilk. Then I'll work on a finding a pitch gauge.
-
I'd like to see you trying a 12-4 or 13-4 APC as an interim sort of deal. I haven't laid hands on the 13-4, but I believe it's a much wider blade. Don't automatically think the "dagger" 12-4 won't work for stunt...they do work on some engines. Apparently, blade area isn't as important as once believed. D>K Steve
-
Excuse the back track here but...is this the BB version of the 61 or the standard Ro-Jett timing version? The higher timed BB version will probably have "BB" or "BB Timing" inscribed somewhere on the case if it is (or at least the ones I have seen do). Not sure if the BB setup will work for a standard timed Ro-Jett. ???
-
Hey Pete! I believe what you're talking about has been covered. The way the engine and pipe are set up now, the engine runs great. My airspeed is just too fast. I will attribute this to me setting everything up according to Bretts SSW post, except the correct prop. If I'm going to set it up the way he did, i also have to use his prop. Which, by the way, has been ordered and will be taken care of.
Steve, i like what your saying. I really need to practise with a plane i know works well before this contest on the 24th-25th. The fact that i have to order props and wait puts this plane out for me. I'll get it going for the next one though. As soon as props come in, I'll update you and let you know what's up.
Also, I'm thinking I'll just have to order that pitch gauge from the UK i told you about. Puts me farther out on this project :(
-
Randy and Brett
If Dane can not get hold of any good CF props, what do you guys think about him using
the XOAR line of props for his set up.
His LHS in the Vegas area should be able to get hold of them with out any problems or
go to Tower for them.
just a suggestion.
Carl
-
Randy and Brett
If Dane can not get hold of any good CF props, what do you guys think about him using
the XOAR line of props for his set up.
His LHS in the Vegas area should be able to get hold of them with out any problems or
go to Tower for them.
just a suggestion.
Carl
It would not hurt a thing to try a 13 x 4, he can run it at 13 inches or cut to 12.5 inches, at least this would give him a base line on that type prop, and also the TF and ProZ props should be close too
Randy
-
Excuse the back track here but...is this the BB version of the 61 or the standard Ro-Jett timing version? The higher timed BB version will probably have "BB" or "BB Timing" inscribed somewhere on the case if it is (or at least the ones I have seen do). Not sure if the BB setup will work for a standard timed Ro-Jett. ???
It's a much better starting point than the "chart" method, because that's how we started, and we have actually run them that way in real life.
The RO-Jett 136-degree version runs a lot more like a PA (since the exhaust timing is the same) than the 140 or 144 version. It actually runs more like a PA61 with the Aussie crank timing modification - because all but the earliest engines run the same crank timing as a QM40 pylon racing engine that is also very close to the VF.
I ran 17.5 on the PA61 as well, and with the Eather pipe Dave and Ted were around 17.75 - but check the pipe tuning article. The slightly extended pipe (compared what you would expect by comparing the duration) reduces the boost/brake a bit to improve the run quality and reduce the tendency to overdo the response. This was all with launch revs in the range of 10,000 or so and pitch around 3.75 to 3.9, and in-flight revs around 10800-11000.
The RO-Jett barstock version, at least, is not prone to a tendency to break into a hard 2-stroke on outsides. The cast-case version, interestingly, *does* seem to have a bit of that, not as bad as the PA61 and nowhere near as bad as the PA40, but it does have that tendency. We were watching Jim Tichy fly his RO-Jett barstock engine up at Napa, and when he got to the square 8, Ted and I both listened for the usual screaming fast outsides, and nothing, just like the 46VF. I was looking around for a cell phone before he got to the 4-leaf because we had never been able to solve it completely on the PA. The later versions of the PA seemed to be a lot better in that regard, and David more-or-less has solved it for the PA75, mostly by finally getting a large enough engine that it can be detuned enough to stay afar away from the break point.
The PA51 never seemed to have the issue to any great degree - probably because of the extended intake duration (almost the same as the 40/46VF) because Brian Eather and Paul Walker both got great improvement by matching the PA51 intake timing. The crank timing modification may have gone a bit too far, because it replicated the PA51 in another way - it tended to start backwards and was able to run fast that way!
There's a lot more to it than just looking at the exhaust duration. In any case, I think you are always better running something that is already proven than starting from scratch with theories. The RO-Jett 61 is clearly the best stunt engine I have ever run, even better than the 40VF.
Brett