Curious what the current favorite is for a starter and battery upgrade for this. Weight savings is a big plus of course.
Before I got this plane, the battery had been relocated aft of the baggage area. I don't like how it performs with the weight back there. I want to move it back to the firewall where I'm told it was before he moved it and upgrade to a lightweight battery.
The starter is beginning to give me hot-start issues so it needs to go ASAP.
I guess that leave the alternator to be upgraded......

Sky-Tec starter
Odyssey SBS J-16 battery
Atlee Dodge Firewall battery box
PlanePower alternator

Zero issues in three years since install.

I have about 120 hours in a '52 170B with a Doyn O-340 installed in 1959. Moving the battery aft of the baggage compartment was part of the Doyn stc in order to keep the CG within the envelope as the hartzell cs prop is quite heavy. If the battery is mounted on the firewall the CG will almost always be forward of the limit and you might like the way it flys even less!

What's the deal with the 340? Thought it was an obsolete motor with some unobtanium prop??? There are a few around all not flying.

I should have noted that I put on a MT prop which helped take 26 lbs. off the nose. Forward CG issue is not a problem now.

Dunno how they work on a 340, but I installed a Skytec "Flyweight" starter on my C150/150's Lyc 320 and it worked great. I also installed an Odyssey SBS J16 battery and mounted it in the aft-located battery box, also worked great. Be sure and clean up all the electrical connections between the two for maximum starting power.

Re a firewall mounted Odyssey-- you might crunch the numbers ahead of time figuring the weight difference of the starters, and weight loss at the aft battery box (and long battery cable), and add in the weigh gain at the firewall for an Odyssey mounted there. You do have a couple options- the Atlee -Dodge firewall battery rack @ $385 is approved for the 170. Burl's makes a similar part but I don't think it's approved for the 170. My current C180 has a firewall-mounted Odyssey, field-approved in what looks like a pre-STC version (or knock-off) of a Burl's battery box. It works fine, but if I was you I think I would look into using the Odyssey "hold down bracket" sold by Spruce (p/n 11-0183) -- light, simple, & cheap at $38.75.

Thanks for the input guys. Exactly what I was looking for.
I wasn't aware the the aft battery location was needed for the Doyne conversion. I was under the impression from the owner that he CHOSE to move the battery there because he could not 3 point it with full flaps (also had leading edge cuffs, stall fences, and droop tips). I will have to do the math on the CG. I certainly dont want to create a new problem (like Z told me, "it's the stuff someone else had to learn the hard way that will kill you).
To answer the prop question: I understand that this WAS the only prop approved and if you need a complete unit its something like $19k. Now there is an MT prop that is approved as I understand it. I would be curious what that cost and the benefits......

The reason I wanted to move the battery back to the firewall is because this plane is a lot more work to wheel land than my Stinson. Ill research and calculate first so I dont kill myself

What's your empty CG value (moment) Jeff? If you compare it to other 170s and it's nearly the same, I would check the control unit between the headset ear cups; it may not have been fully programmed for taildraggers.

One trick I like is to overtrim for wheel or 3-point. I'll dial in more nose down for wheelies and more nose up for 3-point. Make you hold a little control pressure into the flare but then the control forces seem right for the attitude.

My C150/150 was tail-heavy, don't recall the CG location but it was easy to load it out of CG aft. Thought about a firewall battery to move the CG forward, but I rarely flew it with much of a load in back and the airplane flew pretty good as is and I didn't wanna take the chance on screwing that up. Aft CG is supposed to fly faster & stall slower, according to people who should know.

My current C180 is the opposite- CG is pretty far forward. That's actually a good thing, since it has a huge extended baggage which I can fill up with campng gear. I think it'd be just about impossible to load it out of CG aft unless I put in my bowling ball collection or similar. It's not the fastest 180 around, but that forward CG doesn't seem to hurt the stall speed. Wheel lands or three points just fine, even empty.

If I was you, Jeff, I'd crunch the numbers-- if they work out, go ahead & move that battery. A forward CG will give you a lot more loading flexibility. Remember, empty CG doesn't matter-- check it in the most forward scenario, which would probably be a light pilot & minimum fuel. The 170B TCDS shows your CG limits at various weights for both utility & normal categories.

Move the battery to the firewall and use an Odyssey. THEN do a weight and balance. If you're out of fwd CG with just you and gas, put some survival gear in baggage compt. You should already have some there anyway, wherever you fly. That will get you in CG. Life is good.

And, an airplane with a fwd CG flies just fine. Stall speed is a little higher, but they also recover from a stall or spin quicker.

Aft CG, on the other hand, will kill you.

Move the battery, but check the engine STC to verify the battery location. If the STC says battery has to be aft, you'll probably need a field approval to move the battery fwd. That should be easy as long as the empty CG winds up within limits.

MTV

hotrod180 wrote:Remember, empty CG doesn't matter

It matters if you're trying to compare or evaluate 2 aircraft of the same type.

Zzz wrote:What's your empty CG value (moment) Jeff? If you compare it to other 170s and it's nearly the same, I would check the control unit between the headset ear cups; it may not have been fully programmed for taildraggers.

One trick I like is to overtrim for wheel or 3-point. I'll dial in more nose down for wheelies and more nose up for 3-point. Make you hold a little control pressure into the flare but then the control forces seem right for the attitude.

Well, Zane, I guarantee I'm not as good at this as you are. That's one reason I've tried to get the two of us together at different times as I plan to trick you out of some of your knowledge. I'd like to put you in my plane and fly for you and then let you pick me apart.
Fact is, I can wheel land the 170 all the way to a stop. My complaint is that my Stinson requires tons less forward yoke to do the same thing; its just much easier to do with far less forward pressure. This has led me to believe that there is an aft-heavy CG. I have not verified that. The books for that plane are not in front of me right now so I'll have to look it up later.
Even if the STC requires the battery to be in the back, maybe I will be able to improve my perceived balance issue with just a light battery. My preference though would be to have it on the firewall if I can. Where it is now precludes ever doing an extended baggage mod.
Lastly, I do trim in favor of which ever landing style I'm planning. But that is just the sort of not-in-the-books tip I hope to gain by flying with you one of these days.
As to the control unit between the ear cups: you know it need a software update

Zzz wrote:

hotrod180 wrote:Remember, empty CG doesn't matter

It matters if you're trying to compare or evaluate 2 aircraft of the same type.

It also matters if your aircraft Type Certificate specifies an empty aircraft center of gravity range, as many aircraft do.

The Cessna 170 TC does not, however

MTV

I have no worthwhile comments on the battery location, other than to say mine's in back, too. Since I'm driving a trike and am otherwise one of the worst tail dragger pilots around, that's as far as I'll go on that.

However, I can comment about the Skytech starter--mine's been in there 11 1/2 years and almost 800 hours, and it's been 100% trouble free. The only trouble I have had starting was when my old Gill battery was on its last legs about 6 years ago. I replaced it with a Concord AGM, cleaned all of the connections from the master solenoid at the battery box through to the starter, and I haven't had a lick of trouble since.

I also have an alternator conversion. I don't know the brand of the alternator or the conversion itself, other than its a 60 amp alternator that my IA installed 11 1/2 years ago. At the same time, he changed out my fuses and created a subpanel with circuit breakers in it. All that has also given me no trouble at all. It's nice to have the extra capacity, because if I turn on all the electrics including the heated pitot and heated AOA probe and all the lights, that's quite a load--and my alternator still has plenty of reserve capacity to drive all of it.

Cary

Alpina23 wrote:Well, Zane, I guarantee I'm not as good at this as you are. That's one reason I've tried to get the two of us together at different times as I plan to trick you out of some of your knowledge.

I think you overestimate my skills...haha. Either way, let fly together soon. I say don't bother with the battery yet unless you're sure your CG is too far aft. Determine that by comparing to other 170 empty CGs, maybe trade a ride with another local 170 guy to see if it's really the issue.

It's hard to compare two different aircraft types from two different manufacturers and get valuable information other than that they feel different. Now you have me curious though, I need to fly a Stinson 108 to see for myself.

Zzz wrote:

Alpina23 wrote:Well, Zane, I guarantee I'm not as good at this as you are. That's one reason I've tried to get the two of us together at different times as I plan to trick you out of some of your knowledge.

I think you overestimate my skills...haha. Either way, let fly together soon. I say don't bother with the battery yet unless you're sure your CG is too far aft. Determine that by comparing to other 170 empty CGs, maybe trade a ride with another local 170 guy to see if it's really the issue.

It's hard to compare two different aircraft types from two different manufacturers and get valuable information other than that they feel different. Now you have me curious though, I need to fly a Stinson 108 to see for myself.

Come to my house. You can fly both right out of my yard

The first thing you need to do is calculate a weight and balance for YOUR airplane at a couple different common loading screen.

One loading might be just you the pilot and say 20 gallons of gas.....a "coming home" load.

Another might be you, a passenger, full fuel and camping gear.

Do the math on those loads and see where it comes out in center of gravity.

Then calculate a W/B with the battery moved forward. Same loads.

My guess is you'd be fine. Point is, it doesn't make any difference where other airplane's CG is, it's where yours is that matters.

MTV

mtv wrote:

Zzz wrote:

hotrod180 wrote:Remember, empty CG doesn't matter

It matters if you're trying to compare or evaluate 2 aircraft of the same type.

It also matters if your aircraft Type Certificate specifies an empty aircraft center of gravity range, as many aircraft do.
The Cessna 170 TC does not, however MTV

I think my comment was taken a bit out of context.
Empty CG doesn't matter, since as MTV pointed out the TCDS does not specify an empty CG range.
Doesn't matter that much comparing airplanes either, really- what matters is where the CG ends up when your loaded. A forward CG is more important for loading flexibility on a 180 like mine with a big extended baggage, than one with just the stock baggage area.

Alpina23 wrote:....Fact is, I can wheel land the 170 all the way to a stop. My complaint is that my Stinson requires tons less forward yoke to do the same thing; its just much easier to do with far less forward pressure. This has led me to believe that there is an aft-heavy CG. I have not verified that. The books for that plane are not in front of me right now so I'll have to look it up later. .....

I wrote an article several years ago for the C170 Assn newsletter about reweighing my 170 for a new W&B. I still have a copy of it-- FYI it turns out the empty weight (full oil, zero fuel) on my ragwing was 1318# with the CG @ 38.65".

As far as checking your books, I am always skeptical about the W&B sheet. Of the three airplanes that I've owned and personally weighed & done a W&B sheet for, two were screwed up. My 170 was way out of wack- the W&B sheet that came with it showed it weighing about 100# more than it really did. I've seen other airplane's W&B sheets screwed up, understandable after 30 or 40 years of calculating weight plusses and minuses by people with questionable math skills. In fact, I've seen people weighing airplanes for W&B purposes that obviously didn't know what they were doing: incorrectly leveling the airplane, using the wrong datum, and/or weighing it with an unknown amount of fuel on board. It would probably be a good idea to do a re-weigh for your airplane so you have an accurate W&B sheet, esp if you do end up moving the battery.

Eric, while I agree with most of what you've written, I have to stick with my opinion on this. When we're talking about fixed equipment, we have to consider them independent variables. They aren't changeable on a per flight basic like fuel or cargo loading. Two 170's with all other things being equal, yet having different battery locations, should show different empty CGs. We can assume those aircraft will behave slightly differently with the same loading configuration. It's the starting point that can't be altered.

That's why I still think it's a good metric for evaluation.