Archive for the ‘Firewall Forward’ Category

Installed battery box and relays

Saturday, December 23rd, 2006

The battery in the RV-7 lives in a steel box on the forward side of the firewall. The basic box itself comes already formed, spot welded, and powder coated black. You can optionally cut some lightening holes in it, which I chose to do. The combined weight of all the material I removed with my Rotabroach cutter was something like a quarter pound – that's one more cheeseburger I can eat without putting the airplane over its maximum gross weight.

The battery box bolts to the firewall stiffeners through three holes that you have to drill the rivets out of.

Here's the battery box and its steel support angles being fitted to each other and to the firewall. (once again the angle drill was put to work for this task) If you look closely you can just barely see the 0.020" alclad spacer between the firewall and the bracket on the port side of the airplane (right side of this photo) that simulates the thickness of the stainless firewall recess that will eventually be sandwiched between the firewall and the bracket.

Did you notice in the previous photos that the powder coating on the battery box got pretty scratched up while I was cutting the lightening holes? That plus the exposed steel edges inside the holes themselves was enough to make me decide to repaint it. I scuffed it up and sprayed it with a coat of some black high temperature barbeque grill paint that I had in the garage. It seems like it will be fairly durable.

Then I riveted on the support angles and nutplates – in that order, since the nutplates block access to some of the other rivets. You also have to remember to dimple the box and angles from the inside out, so the flush heads will let the battery slide in and out without getting hung up.

Lots of careful measuring is required to properly position the holes for mounting the master and starter relays. The outer two holes go through the firewall stiffeners, and the inner two holes go through this little 0.063" doubler. Also, the two circled rivets have to be drilled out so the two outer nutplates can be attached to the stiffeners.

Here's the doubler, primed and with the 1/4" nutplates attached. This gets riveted to the aft side of the firewall.

Here's the battery box, master relay (silver), and starter relay (black) bolted in place. What's interesting is that the heavy battery (14 pounds or thereabouts) is held to the firewall with three 3/16" bolts, and the comparatively lightweight relays (about a pound each) are held in place with a pair of 1/4" bolts apiece. I hope that battery doesn't go anywhere or I shall be sorely put out.

Also worth recording is the fact that I bought my master relay from B&C instead of Van's, since it's an important component and Van's is known for carrying cheap stuff (IMHO). It was almost twice as expensive, and it actually may not be any more reliable, but it makes me feel better to have it. The mounting holes are identical to the one Van's sells so no problem there.

The starter relay, on the other hand, is Van's stock item. The one that B&C sells appears to have totally different mounting lugs, so it would have been a pain to install, and I'm a lot less worried about safety implications of my starter relay conking out.

Installed the engine mount

Saturday, December 16th, 2006

I made two bushings out of 3/8" OD 0.058" wall steel tube, each about two and a half inches long. 1/4" bolts fit nicely inside.

I used the bushings and bolts to temporarily attach the mount to the firewall, using the pre-drilled 1/4" holes. I used the two upper corners for this, but I think you could do it with whichever pair of holes lines up best.

Immediately it became apparent that I needed to remove some of the firewall flange at the lower corners where the gear sockets are. Checkoway has a better photo on his site. I used a grinding thingy in my Dremel to make the rough shape, then filed and scotchbrited it smooth. I think I'll have to come back and open this up further when I go to insert the gear legs, but right now it's trimmed enough to at least get the engine mount onto the firewall.

One hole at a time, I drilled up to just a bit less than 3/8" using a U-size drill bit (0.368") then reamed up to 0.375". At the two lower center bolt locations, the mount was spaced away from the firewall a bit, so I made some spacers out of alclad scraps. I think I used 0.032" for one and 0.016" for the other.

After the holes were drilled, I made the spacers all round and pretty:

Huzzah, the engine mount is on the fuselage. I didn't torque or safety the bolts, as I'm sure I'll have it on and off a few times before it's bolted on for good.

Yep, it's plenty strong.

Installed cowl hinges on firewall

Sunday, December 10th, 2006

The next milestone in this little odyssey is to get the engine mount installed. But I decided to first install the hinges that will attach the lower part of the cowling to the firewall. Others have reported problems getting enough access to set the rivets once the engine mount is in place, so I figured why not save myself some trouble and avoid that problem entirely.

The plans don't actually tell you how long to make each of the four hinge pieces that are required, but I was able to puzzle it out by looking at the rivet callouts on drawing 28. I clamped each piece to the outside face of the firewall flange and back drilled using the prepunched and pre-dimpled holes as a gude.

Before I put in the rivets that attach the fuselage side skins to the firewall, I squeezed a bead of red RTV in the gap between the two surfaces, to help seal the cabin from exhaust fumes and smoke (hopefully not applicable). The lower flange seems to have been sealed with proseal by the quickbuild factory, but I don't think proseal is especially heat-resistant so I went with the high-temp RTV.

Here the hinges have been riveted to the side and bottom firewall flanges.

At both of the bottom corners of the firewall, I laid down a fairly thick fillet of RTV to cover over a gap that was about 1/16" on both sides. A lot of nasty fumes could have gotten in through here. Also, if I was smart I would have waited until the glue was dry before doing stuff that made drill chips, but oh well.

I turned off the shop lights and put my work light inside the fuselage to look for unsealed gaps. The only light coming from the sides and bottom of the firewall was through the engine mount bolt holes, so I'd say this part of the firewall is sealed.

While I had the RTV uncorked I put down another fillet to seal around the hole in the firewall where the brake fluid reservoir pokes through.

Of course as soon as I started trial-fitting the engine mount, I discovered that the taildragger gear leg sockets interefered with the outermost hinge eyelets, so I had to cut off part of my newly installed hinges. Oh well, it's easier to make them shorter than longer.

The engine mount is attached to the fuselage with six 3/8" bolts. In four of those locations, there are 1/4" pilot holes already drilled by the quickbuilders. I think what I'll do in order to get a perfect fit is grab some steel tubing from Airparts and make up some 3/8" OD, 1/4" ID bushings. That should let me bolt the mount to the firewall through two or more of the undersized pilot holes, the drill and ream each hole up to final size without worrying about how to clamp the mount to the fuselage.

Firewall forward kit contents

Monday, November 27th, 2006

I asked Van's to email me a list of the IO-360-M1B firewall forward kit contents. For my own future reference, here it is along with my notes:

1.000 CT BLK THROTTLE 50.5 throttle cable
1.000 CT RED VMIXTURE 50.5 mixture cable
1.000 FAB-HORIZ INDUCTION-1 airbox
1.000 IO-360 THROTTLE/MIX cable brackets
1.000 PLASTIC TIE WRAP 5.5"
1.000 VA-136 23" fuel line
1.000 VA-138 14" fuel line
1.000 PROP GOV MT P-860-4 hydraulic governor
1.000 VA-183-PC bracket for governor
1.000 BAF-6-360 cooling baffle kit
1.000 CT BLUE VPROP 48 prop cable
1.000 F.WALL FWD COM M1B 7 some kind of hardware assortment?
1.000 AT0-028X3/16X6 aluminum tube
1.000 AT6-058X5/16X15 7/8 aluminum tube
2.000 SS304-26GAX1/2X9 stainless ???
1.000 FF 3/4 FIREWALL PLUG
1.000 ES PC680 INSTALL KIT battery box
1.000 EA LV-1 HEAT SHIELD exhaust pipe heat shield
2.000 CT A-740 BLACK heat control cable
1.000 DUCT CBT-5/8 corrugated blast tube
1.000 EA CV HOSE 9816 breather hose
1.000 EA DYNA BOLT bolt set for Dynafocal engine mount
4.000 EA DYNA VI-STD Dynafocal vibration isolator
1.000 EA EXH 7/7A IO-360M1B Vetterman crossover exhaust with heat muff
1.000 EA OIL COOLER II oil cooler, cheap knockoff of Stewart Warner 7-row model
1.000 ES 24021 starter solenoid
1.000 ES 24115 master relay
1.000 ES ALTERNATOR 60A KIT alternator for a 1987 Suzuki Samurai
1.000 ES WH 6/7/9 KIT wiring harness kit
1.000 FF-705 breather tube
1.000 FF-709 oil cooler doubler
1.000 IE VMP INSTALL KIT manifold pressure gauge install kit
1.000 PT-035X1/4X12 plastic tube
1.000 VA-102 15.5" fuel pressure hose
1.000 VA-168 transducer manifold
1.000 VA-133 27.25" oil pressure hose
1.000 VA-134 19" oil cooler hose
1.000 VA-135 16.5" oil cooler hose
1.000 VENT DL-03 2" SCAT tube flange
1.000 VENT SCAT 2X6' 6' of 2" SCAT tube
1.000 VENT TG-10 heater valve
1.000 AS3-063X1 1/2X4 0.063" Alclad
1.000 AT0-035X3/8X24 aluminum tube
0.500 F AE102-11 firesleeve
0.250 EA HOSE H177 ???
1.000 BAG 626-1
1.000 BAG 627-1
1.000 BAG 628
1.000 BAG 629
1.000 BAG 958
1.000 BAG 991
1.000 BAG 1934
1.000 BAG 1935
1.000 BAG 1978
1.000 BAG 1979
1.000 AS3-063X1X12 0.063" Alclad
1.000 CT BEARING HWR, PROP prop governor attach hardware
1.000 CT BEARING MW-3M rod end bearing
1.000 DOC FWF COMPLETE FWF plans

Ordered engine

Wednesday, November 15th, 2006

I ordered my engine from Mattituck today:

Scheduled delivery is for the third week in January.