Engine mounting and pushrod setup
 

This is a replicate post from the ARF section because I didnt get a reply there

1) Trying to install a DLE20 on a GP 90-120 adjustable mount. Its about 2mm too narrow and a larger mount will require surgery on the firewall. Cant make it wider because that would require to drill out the interlocking tabs on the back of the mount, so it wouldnt be secure enough. Should I simply grind / sand 2mm each side off the beams? The mounting holes seem to be further inside the beam so that wouldnt be an issue. Will the mount retain sufficient strength after this?

2) The manual requires you to solder one end clevis. I dont know how to solder or have the tools, but I do have Sullivan SS 4-40 full threaded pushrods and Dubro spring steel clevises which I had bought for ease of adjustment. I am also using Dubro large scale black horns on all surfaces.

http://www3.towerhobbies.com/cgi-bin...?&I=LXD875&P=7
http://www3.towerhobbies.com/cgi-bin...&I=LXD937&P=ML
http://www3.towerhobbies.com/cgi-bin...?&I=LXFV03&P=7

Now, some senior modellers told me that I shouldnt use the full threaded rods as they are prone to corrosion due to humid weather and snapping due to the threading reducing cross-section area. Was wondering- this is stainless steel, should be more resistant to corrosion and stronger than standard MS pushrod, shouldnt it? Also, will this this pushrods really snap?. I was planning to cover the unused threads with oil paint or sleeve with silicon tubing after I am done adjusting to protect from the environment. I have one side threaded rods as well but putting Z-bends are difficult because I am using the outermost hole on the servo (see pic) which will need to be enlarged for the pushrod and I dont think its strong enough. So should I use the full threaded ones?

Ameyam

RE: Engine mounting and pushrod setup
 

as for the pushrods don't use full threaded rods they can break over time, like your senior modelers advised you,

if you need to install another mount just pop out the blind nuts in the back of the firewall and epoxy some wood in the holes then just re-drill the holes for the new mount there easy to do if there is already existing holes drilled

RE: Engine mounting and pushrod setup
 

What are the other options I have regarding the pushrods, Tim? Look at the picture, the horn just about projects out of the servo plate. I dont think the stock futaba 4-armed servo arm has the strength after the outermost hole has been drilled out to 4-40 size.

With the engine mount, its not that simple. The fuse has 4 hardwood blocks pasted on the inside of the firewall onto which the blind nuts hold. When I was setting up for gas, I fibreglassed over these. I can probably remove them with a dremel. Issue is the difference in mounting dimensions between the 180 mount and the 120 mount is so small, I will end up with an oval hole or slot rather than a new hole. Another point is once I fill the old hole and try to drill a new one, I will be drilling on the glue line which will cause the drill to meander either side of the glue line even with a steady hand as the glue will be harder than the wood

I am attaching a couple of pics with the stock mount temporarily installed at the widest and the DLE20 proven mount held over for comparison- its just 2mm each side. I may also not need to grind the entire beam, jut the interfering bit. In the second pic, I just made a couple of dents using the dle mount as a guide, dont know whether you can see them. I think they are well inside the beam

Ameyam

RE: Engine mounting and pushrod setup
 

Hey, should I use JBWeld instead of solder on the stock pushrods?

Ameyam

RE: Engine mounting and pushrod setup
 

first I wouldn't use JB Weld soldering is easy it just takes a little practice, with the servo arms, I usually junk them when I do the"through the servo mount plate installation and replace them with Dubro HD servo arms http://www3.towerhobbies.com/cgi-bin...?&I=LXD668&P=7 there thicker and slightly longer than the stock futaba arms and there will be plenty of plastic when drilling out for 4-40 rods.

a alternative to soldering would be to use a standard pushrod with a clevis screwed onto one end and make a Z bend or use a quick link after making a single bend using these http://www3.towerhobbies.com/cgi-bin...?&I=LXEMG3&P=7 I use them all the time they work great and for added security you just slip some fuel tubing over the end snapped onto the pushrod and it will last for a long time.

as for the mount, your better off making the mounting holes to the firewall larger, than shaving any material off the beams

if you can not move the mounting bolt locations,make sure if you open up the holes in the back of the mount you use a larger washer to spread the load since the bolt pattern will be more narrow