starter/battery cg

Ask Questions and Offer Advice Related to the Cessna 120 & 140 Type

Moderators: 6643, 6183, V529

Forum rules
You must be a member of the Cessna 120-140 Association in order to post new topics, reply to existing topics, or search for information on this forum. Use the "Join" link in the red menu bar.
Post Reply
User avatar
VIP620
Posts: 40
Joined: Tue May 01, 2018 7:00 am
Location: 69nd
Name: ken tengesdal
Aircraft Type: 120
Occupation-Interests: fly the 120 over sunflower fields and shoot blackbirds at the same time from august thru october or until the crop is harvested
Contact:

starter/battery cg

Post by VIP620 »

my current cg is 12.8 and if i stay at that cg and add a starter (9.2 lb) and battery (pc 680, 15 lb), to maintain original cg, the battery would be placed 22.5 inches. correct or wrong?
User avatar
6643
Posts: 2326
Joined: Tue May 01, 2018 7:00 am
Location: KLCI
Name: John C
Aircraft Type: 1946 C140/C90
Occupation-Interests: A&P, semi-retired
Contact:

Re: starter/battery cg

Post by 6643 »

Not enough information. How much does the plane weigh? Do you currently have a starter and battery you are removing? How much do they weigh, and what is the arm for each? Will the arm for the new items be the same?
User avatar
VIP620
Posts: 40
Joined: Tue May 01, 2018 7:00 am
Location: 69nd
Name: ken tengesdal
Aircraft Type: 120
Occupation-Interests: fly the 120 over sunflower fields and shoot blackbirds at the same time from august thru october or until the crop is harvested
Contact:

Re: starter/battery cg

Post by VIP620 »

non electric from factory, c85, so starter should be around 24" from datum. trying to figure where the battery will go, to find battery cable length and maintain original cg
User avatar
6643
Posts: 2326
Joined: Tue May 01, 2018 7:00 am
Location: KLCI
Name: John C
Aircraft Type: 1946 C140/C90
Occupation-Interests: A&P, semi-retired
Contact:

Re: starter/battery cg

Post by 6643 »

The starter is forward (-25). The light weight starter is probably a few inches farther forward)) so the battery should be aft to balance. Original battery box is +56. Using these arms and your weights your CG will shift slightly aft to about 13.1". Putting the battery at +25 will put you about 12.6" but you'd be sitting on it... 13.1 is well within the acceptable range.
User avatar
VIP620
Posts: 40
Joined: Tue May 01, 2018 7:00 am
Location: 69nd
Name: ken tengesdal
Aircraft Type: 120
Occupation-Interests: fly the 120 over sunflower fields and shoot blackbirds at the same time from august thru october or until the crop is harvested
Contact:

Re: starter/battery cg

Post by VIP620 »

thanks, i'm thinking under the seat. i have the spring seats instead of the cushion type, so there is plenty of room with battery laying or mounted on it's side
Post Reply

Who is online

Users browsing this forum: No registered users and 12 guests