The International Cessna^® 170 Association

How does the engine bond to the fuselage on the B model? The parts manual is not very detailed. Also the engine mount "floats" in rubber mounts so it too needs to be bonded to the fuselage and engine. Any help appreciated.

marstall wrote:How does the engine bond to the fuselage on the B model? The parts manual is not very detailed. Also the engine mount "floats" in rubber mounts so it too needs to be bonded to the fuselage and engine. Any help appreciated.

Nomaly there is an aluminum strap on the right lower side that bonds the motor mount to the fuselage...Brad
I came back to edit my last post.....I think I would use float plane gromets....AL..... and you don't have the worry of bonding the motor mount....just my thoughts....Brad

I put 4 straps from the engine to the mount, and 4 straps mount to firewall. If yours are missing or broken, they are easy to fabricate out of sheet aluminum. Check out my post at this thread:

http://www.cessna170.org/forums/viewtop ... ound+strap

Miles

cessna170bdriver wrote: Check out my post at this thread:

http://www.cessna170.org/forums/viewtop ... ound+strap

Miles

Miles I knew I'd seen a picture of that rap around ground for the motor mount somewhere but when I couldn't find it in the IPC I was wondering where.

The engine mounts have small, aluminum "jumper' straps that jump across the rubber Lord mounts, but the engine itself is grounded from the accy-case to the firewall (at the same place as the battery) with either a copper cable, or a braided one.

Many thanks to everyone for the responses and photos. That is exactly what I needed.

gahorn wrote:The engine mounts have small, aluminum "jumper' straps that jump across the rubber Lord mounts, but the engine itself is grounded from the accy-case to the firewall (at the same place as the battery) with either a copper cable, or a braided one.

George,
Not originally, everyone has added a strap to the Acc case....just makes sense....the photo shows the only original grounding from the mount to the fire wall....Brad

Brad Brady wrote: everyone has added a strap to the Acc case....just makes sense....the photo shows the only original grounding from the mount to the fire wall....Brad

Not everyone... Four of those aluminum straps have been working for me for 27+ years.

Miles

cessna170bdriver wrote:

Brad Brady wrote: everyone has added a strap to the Acc case....just makes sense....the photo shows the only original grounding from the mount to the fire wall....Brad

Not everyone... Four of those aluminum straps have been working for me for 27+ years.

Miles

Well Miles,
You have four, the photo I showed is what Cessna thought was good enough in 1954 ...Brad

Well, just to be accurate...
NONE of the various 170 IPC's illustrate ANY grounding or bonding straps at the engine mount-to-firewall connections. The only bonding straps called for in the IPC are those at the "lord" mounts at the engine-to-mount shock mounts.

The engine installation figures in all three IPC's do not show any bonding/grounding straps either, except as just mentioned.

The 100 series Service Manual does discuss bonding straps at mount-to-firewall in certain aircraft, however does not mention the 170. It merely states to replace them with like/similar units as originally found. It also states on page 12-33 "Note Some ground straps are of braided costruction. When replacing, use whatever type was originally installed."

None of the electrical diagrams illustrate any engine-to-airframe ground at all.

Mine is grounded via a #2 copper cable and appropriate terminals, connecting the engine accy. case to the firewall at the same location as the battery ground-strap.