davey_flyer

My Feedback: (4)

on the throttle and choke they are spring loaded, are we supposed to remove the springs before setting up with servos?


Thx

barryb-RCU

The popular view is that you are to unwind the spring. Don't remove it as the spring needs to continue to hold the arm away from the carb.

Personally, I leave the spring on. Always. The reason I do this is that the spring eliminates geartrain and linkage slop -- the slop is always pushed to the side.

On extremely high thrust to weight setups the extra precision makes a lot of difference when you're working on hovering and tailslides.

davey_flyer

My Feedback: (4)

Ok thanks but doesn't the spring provide a certain amount of push constantly on the servo and is this not bad for the servo?

David

EJB

Just unhook one end of the spring & leave it on - no big deal.The choke "snaps" open or closed - it's either open or closed,so don't muck with it.

MCR-RCU

My Feedback: (2)

David, I just ordered one today.

Can you tell me how far it is from the rear mounting lugs to the end of the carb? There drawing on RCS shows the 6" length from the mounting surface to the prop adapter, but it doesn't show me how far I need to be away from firewall to clear the carb.

I'm trying to figure out how long a stand-off I will need to mount to a solid firewall with no hole in it for the carb to go into.

Are you going to be mounting it direct or did you buy that aluminum mount that RCS sells?

Thanks,
Marty

davey_flyer

My Feedback: (4)

I made a mount for it out of 1.25" dowel, but I don't know if that's strong enough and I might try something different. The measurement is: 2.5" from the mounts to the back of the carb.

D

DENNIS C

My Feedback: (99)

hey marty

i got one in my hand right now and it measures 2 1/4 ins from the back surface of the mount to the rear of the carb including the head of the bolts.

hope yor not confused

davey_flyer

My Feedback: (4)

yeah but when you open the choke the butterfly sticks out another 1/4"...

DENNIS C

My Feedback: (99)

davey-flyer

ya your right did'nt think about that sorry now i'am confused lol

MCR-RCU

My Feedback: (2)

Thanks guys. Sounds like I need 3" standoffs to clear the firewall enough to still let the carb breath. Does this sound right?

Thanks again,
Marty

Big_Bird

My Feedback: (1)

What minimum distance from the carb to the solid firewall would provide adequate air flow at full throttle?

Ken

davey_flyer

My Feedback: (4)

I think that depends on the amount of flow you have coming through the cowl. But I would leave at least 3/4"...

xp8103

My Feedback: (16)

Marty,
Well... That would also depend on what plane you are putting the engine in. 3" may cause the engine to stick out 2 inches past the cowling.

MCR-RCU

My Feedback: (2)

I'm putting it into a Byron Sukhoi that had a Precision Eagle 4.2 w/PurrPower muffler system in it. The plane flew pretty well with the 4.2, but could use a little more power. Plus the 4.2 & muffler are quite heavy. It's no 3D plane by any means but it is a good smooth flyer.

I'm in the process of planning out a new motor box to replace the Purr Power mounts. Can anyone tell me what size bolts the mounting lugs on the engine are sized for? 1/4" or #10 or what?

Thanks,
Marty

Smokey

My Feedback: (16)

I spoke to RCshowcase yesterday at the Wram show. I asked them the very question. They said 1 1/2" is ideal.

Smokey

davey_flyer

My Feedback: (4)

marty I went through this yesterday - you need #10 bolts - 1/4 is too big. And as stick jammer told me, get the black hardened ones with the allen head - they're much stronger.


David

Big_Bird

My Feedback: (1)

At this point I may have painted myself into a corner by ordering a ZDZ80 from RCS (supposed to be delivered in March).

Here's the problem: The plane that this engine is supposed to go in is a 33% Hostetler Super Decathlon that I'm currently building. The engine measures 6" from the mount to the spinner backplate. I only have 8 1/4" from the firewall to the spinner backplate. If I mount the engine 2 1/4" from the firewall I need to cut a hole in the firewall for the carb. From my scaling the drawing, it looks like I can cut a 2 3/4" hole in the firewall.

I have a big concern about the possibility of fire since I read that someone had a cowl fire with a ZDZ80. I have thought of putting something like a (don't laugh) soup can behind the firewall to seal off the engine from the cabin. Is my fear of fire valid with this engine?

In order to look right, I don't want to move the cowl forward and I really don't want to give up on this engine and cancel the order. Any ideas will be appreciated.

Thanks,
Ken

Forgues Research

My Feedback: (7)

Marty,
I have been making these standoffs for a long time for these engines. 3/4" is all you need for clearance to the firewall. But its your call. I can make these any lenght you need, as I make them custom to order.
standoffs

Diablo-RCU

My Feedback: (1)

Fear of fire:
I've got a H9 Cap with a ZDZ-80 mounted on aluminum standoffs. The carb is close enough to the firewall so that I cut a large hole in the firewall so the engine could breathe. The danger from fire is no greater than any other gas engine, just make sure you haven't screwed up the ignition timing. I don't believe you could set the timing so the engine would backfire through the carb, because the transfer ports would have to be open and there's not enough range on the sensor position. It could shoot fire out of the exhaust pipes....just like every other gasser. Anyway, 250 flights....no fires.

EJB

Ken,
I woudn't worry too much about fire.Have not seen a fire on a gasser yet.Just make sure you "fuel-proof" inside the cabin.Gas does drip from the carb after choking so you might want to provide a "drain hole" on the bottom of the fuse.

Big_Bird

My Feedback: (1)

I started flying Giant Scale in 1982 with a Quadra 35 in a Nosen Citabria and have also never seen a fire in a gasoline powered plane. So, Guess I'll won't worry about it.

I still think the short piece of can behind the engine would be a good idea to keep any gasoline out of the cabin. I would cut the hole in the firewall so that the can just slipped in side it and then I would glue it in.

To get maximum cooling for the engine I am planning to build an air dam into the cowl so that all of the incoming air is forced to exit around the fins. I also have an air chute behind the engine just like on the full scale Decathlon.

Ken