Thorp Air Command - T18.net

Supporting Owners, Builders and Pilots of the Thorp T-18 and its variants.
It is currently Thu Mar 28, 2024 6:35 am

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 8 posts ] 
Author Message
Binder
PostPosted: Fri Feb 02, 2018 8:39 am 
Sr. Member
Sr. Member

Joined: Thu Sep 01, 2016 10:50 pm
Posts: 257
So after rewiring most of my plane and having it back in the air since fall I'm starting to get annoyed wi my slow trim. Prior to moving the battery to the firewall I needed little to no trim. Now I'm adjusting the trim more from take off, cruise and landing. I have plenty of trim although now that I'm using it I have noticed it's very slow. Mine has the normal jack screw with electric motor that is mounted just behind my baggage bulkhead.

I have a 14g power wire running to my stick mounted switch then back to the motor. My first steps are to pull the wires at the motor to verify my voltage drop across those wires although I think a 14g should be plenty. That being said the tiny switch in my control stick could be a bottleneck although it's only a short contact.

Is anyone else using a relay from the control stick switch or just straight from power to switch to motor?


If the voltage looks good my next thoughts are checking the electrical brushes in the motor for wear or even putting a faster motor in. I'll have to verify the model motor mine has. I couldn't find anything with a quick glance when I was wiring.

Thanks all!


Top
 Profile  
 
Jeff J
PostPosted: Fri Feb 02, 2018 10:26 am 
Sr. Member
Sr. Member

Joined: Wed Aug 31, 2016 8:18 am
Posts: 583
Images: 0
Location: eastern OK
I would think 14 gauge wire is heavy enough but need to know how many amps the motor can draw and how long the wire is to verify gauge needed. You could be right about the switch if it wasn’t designed to carry the load.

_________________
Thorp T18
O-320-B3B (160 HP)
68x74 Sterba Propeller

"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson


Top
 Profile Personal album  
 
Fraser MacPhee
PostPosted: Fri Feb 02, 2018 10:56 am 
Sr. Member
Sr. Member

Joined: Wed Oct 21, 2009 8:57 am
Posts: 722
Images: 19
Location: USA
For what it's worth, my electric trim is 12 seconds stop to stop - I actually wish I had manual trim, as bumping the electrical trim rarely results in level flight at cruise, which is then needing another change once another 6 lbs has burned off 8 minutes later in the header tank. I think slow trim is a good thing in a T-18.

_________________
Fraser MacPhee
N926WM
Serial #279-1
Angel Fire, NM (KAXX)


Top
 Profile Personal album  
 
Ryan Allen
PostPosted: Fri Feb 02, 2018 12:36 pm 
Hero Member
Hero Member
User avatar

Joined: Wed Oct 21, 2009 6:10 pm
Posts: 1105
Images: 0
Location: Louisiana
I fly another airplane where I cant ever get the trim where I want it because the trim moves too fast. Makes me appreciate my slow Thorp trim motor.


Top
 Profile Personal album  
 
Binder
PostPosted: Fri Feb 02, 2018 6:21 pm 
Sr. Member
Sr. Member

Joined: Thu Sep 01, 2016 10:50 pm
Posts: 257
Jeff J wrote:
I would think 14 gauge wire is heavy enough but need to know how many amps the motor can draw and how long the wire is to verify gauge needed. You could be right about the switch if it wasn’t designed to carry the load.



This looks like the original motor from the build in the 70s but I can't see markings. Next week I'll get pictures and see if there is a stamp somewhere. It hasn't tripped the 5amp breaker so it has to be less than that

The slow trim is nice in flight but I struggle on take off. If the trim isn't perfect I have to hold way too much forward pressure and it takes a good 30 seconds to level out. My trim indicator is skipping teeth so it's not accurate and my landing trim is very tail heavy. So rich and go landings don't have enough time to trim level. I can hold the pressure but if I were to slip or something happen I think there is potential for a safety hazard. It doesn't feel unsafe but I don't like any potential.

It might all balance out once I remove as all my bad stuff as and change lighter avionics as planned here in a few months though. I was just hoping for more like 15 seconds trim travel and not 30+


Top
 Profile  
 
Binder
PostPosted: Fri Feb 02, 2018 6:22 pm 
Sr. Member
Sr. Member

Joined: Thu Sep 01, 2016 10:50 pm
Posts: 257
I prefer manual trim and manual flaps in my planes as well but Thorpe has right tight estate


Top
 Profile  
 
Jeff J
PostPosted: Fri Feb 02, 2018 8:28 pm 
Sr. Member
Sr. Member

Joined: Wed Aug 31, 2016 8:18 am
Posts: 583
Images: 0
Location: eastern OK
Using 5 amps and 12 feet as the wire length from the bus to the motor, 18 gauge would carry a continuous load just fine. 14 gauge will carry a continuous load of 5 amps for 25 feet before heavier wire is needed. A trim motor would be intermittent use and allow smaller wire (18 gauge for 25 feet at 5 amps).

_________________
Thorp T18
O-320-B3B (160 HP)
68x74 Sterba Propeller

"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson


Top
 Profile Personal album  
 
Binder
PostPosted: Sat Feb 03, 2018 9:00 am 
Sr. Member
Sr. Member

Joined: Thu Sep 01, 2016 10:50 pm
Posts: 257
Ya, that's what I thought. I went through all the charts on wire gauge and resistance to make sure I sized everything by the book with breakers designed for wire current safety and not just random amounts.

I'll pull my inspection hole and put s little live in the jackshaft. That might be slowing it down as well since it's so cold and I'm not sure how well it was lubed during the inspection.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 8 posts ] 

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 10 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron

[ Time : 0.150s | 12 Queries | GZIP : On ]