Titan 33 gets a little upgrade

[Chilli]

Well I'm home from work since the wife is not feeling well and the little monsters are still in school so I thought I would share a few lessons learned and a few upgrades I made to my Titan 33.

Based on what I have read on this board I knew the .150 flex I was using with my 1515 1y was the weak link in my drive line. I did not install the .187 flex when I built the boat because I did not originally plan on Neu power and Lipo packs at the time of the build. I resisted upgrading the flex since I didn’t like the ideal of ripping out the stuffing tube and replacing it with a larger one. Once again I learned that if you know something needs to be fixed or upgraded and you don't do it, the justification will be done for you. My flex snapped and what you see is in the enclosed picture. The flex wrapped around my ESC cable and also totally shredded the stuffing tube that was exposed outside of the wooden stuffing tube support.

Well what to do now.... The logical choice was to install a .187 flex. But I wanted to get back on the water as soon as possible and Steve didn’t have everything I needed in stock. The only other option was a piano wire drive. I was never keen on the idea of wire drive. There are not many build threads that have them. Also, I have a Fine Design strut. How am I going to make that work with the small stuffing tube required for the wire drive? Well, after some late night web surfing and a few emails to Jeff Wohlt I decide to take the plunge. I ordered a .078 wire drive system and coupler from Jeff and some brass tubing (5/32 and 3/16) from OSE. I also decided to go without Teflon which is another first for me. I ripped out the old stuffing tube and supports. I cut a short piece of the 3/16 tubing and slid it about 1/8" inside the nose of the strut. The other end ended up being about 1/2" inside the transom. Then I slide the 5/32 main stuffing tub inside the 3/16 tube making sure the tube ends were even inside the strut. Then I epoxied everything into place. I trimmed the 5/32 to the appropriate length at the coupler and slid another short piece of 3/16 at that end for some additional strength and support. I installed a new plywood stuffing tube support on the coupler end and shrink wrapped the 3/16 tube at the strut and I'm back in business. I'm just waiting for a drive dog to arrive from OSE. Those of you contemplating wire drive, remember it's only good in installations where there is only a little bend in the drive line.

Now another thing I noticed when I was assessing the damage on my boat was that if I put any torsional force on my motor (grab it and twist), the hull flexed and the motor moved a little. This may have also contributed to the demise of my flex cable. So I fabricated some marine plywood rails. Soaked them in penetrating epoxy. Painted them up and epoxied them into the boat. Now the flex on the hull is much reduced.

Lastly I added a little lead to the boat to keep here a little more stable at speed in race water. I have about 15 ounces in there. CG is about 31% without batteries.

Thanks to Jeff Wohlt for his guidance on the wire drive and Egneg who’s massaged X640 I will get to try out this weekend. Gurus, feel free to correct me if anything looks amiss or I passed on any bum info.

[j.m.]

Looks good!! I'm glad to see another wire drive out there!

[Jeff Wohlt]

Nice set up. let us know how it goes.

[Chilli]

We'll first run with the wire drive today. I had one little problem with the installation that I thought I licked but it ended up biting me in the butt. When I installed the wire drive into the strut, the prop shaft was tight fitting into the strut. I put the wire drive in a drill and pinched the shaft with some 1200 grit wet/dry sandpaper and thought I took off enough metal. Though not loose, the shaft spun well and did not appear tight. But I guess the clearance was still too tight and after about two laps, I blew the Etti. I couldnt figure out why it happened unitill I tried to spin the prop and it was very tight. On the plus side I was impressed with the strength of Jeff's wire drive and the coupler. Look at the striations on the wire in the enclosed pictures. I must of twisted that 078 wire at least a half dozen times. The nitro guys were impressed with the torque of the Neu. They said they never saw a wire drive do that. Also notice the brass from the strut on the front of the shaft. The Etti got so hot the negative battery wire solder melted and the boat died. The ESC blew about a minute later when I was going to retrieve the boat. I separated the boards to survey the damage. Notice it wasnt caps that blew. Oh well, expect another order on Monday Steve.

[Meniscus]

Wow!!!

=> that's all I can say!

[egneg]

I guess I made you a killer prop

[Chilli]

Now thats funny!!!!

[Jeff Wohlt]

wow...WTF??? What is the strut and is it what bushing set up? Just a regular 3/16 shaft that is the typical std size.....what went wrong? Why was that tight to begin with?

I assume it was greased well?

This may be a heating up issue in the bushing and expanded or something to gaul that shaft and make it tight like that. Hope this is not a set up running the stuffing tube thru the strut and also a bushing inside that.

We need to know what bushing set up that is using.

Well at least it is good to know that the 78 wire will hold up better than a 187 cable!

After review I am thinking you have an issue (ha... no sh-t) but I mean you already broke a 187 which is one strong cable and now this. Something else may be happening...Not sure what but breaking that cable leads me to think a strut issue. Maybe it needs drilling out and a good speed bushing put in.

[Chilli]

The orginial flex I snaped was a Octura .150 flex, not the .187 and it was a bit snug pushing it in for the first time. But after a few twists, it loosened up and I got about 20 runs on it before it failed. I assumed the failure was due to the .150 flex not being up to the 1515 1y I'm running.

I'm using a Fine Design strut. It's the first strut/rudder combo listed on this web page.

http://www.finedesignrc.com/hardware.asp

It uses a two piece 3/16 ID brass bushing. It has a bullet nose that gets pressed in from the front and a sleeve that gets pressed in flush from the rear. Inside the strut bore there is about a 3/16 (estimate) gap between the front and rear bushing. The shaft I got from you was REAL tight so I sanded it down with 1500 grit (not 1200 I mentioned in my earlier post) till I could spin it around without feeling any binding. I did grease the shaft well as always, but you'll notice the gaul was at the front of the shaft. I'm thinking the fit was still tight and the grease was wiped off by the time the shaft got pushed into the correct position. Then came heat, expansion, and then it locked up.

Well, it's late and I have to work OT tomorrow to pay for my new Etti AND I have to figure out what I'm going to do. Maybe have the POS drilled out for a speedmaster bushing. And I'm also hoping I didnt hose up my Motor. What a PITA. But it's all good. Problem identified and we'll get it squared away. I'm just wearing the Milkbone underwear this week.........

[Jeff Wohlt]

So the shafts runs in the nose piece as a bushing and then the rear has its own bushing? They were originally made to run in the brass nose (octura and hughey) as a bushing but I drill mine out so it does not. I only want it to run in the sleeve bushing. Torque from the prop shaft will put a bind on the front and rear bushing and this is common but too tight and things heat up.

There should be a slight amount of space/slop when the shaft is in.

[Chilli]

The shaft runs about a quarter inch inside the rear of the front bushing. If it did'nt, the shaft would be way too long comming out of the back of the strut. I wonder if the strut was designed for a shorter shaft. Fine Design sells the Hughey flex. I don't know if its the same dimensions as the Octura. Nonetheless, there was definely was no slop (front or rear bushing) in this set up. It's nothing like the Speedmaster set up in my sons boat.

So my options are:
1. Drill out the front and rear bushing so the shaft has some play.
2. Drill out the rear bushing for play and open the front one up even more so the shaft only rides on the rear bushing.
3. Machine the strut and bushings to accept a speedmaster bushing.
4. Can the FD strut and switch back to Speedmaster. (not an option till the end of the season)

[Jeff Wohlt]

What is the length of the strut without nose? I have made shorter ones in the past for people. the hughey shaft has an even smaller end for that in the nose.

I would put a speed bushing in it. If oyu want to send me the strut I will make it perfect for you. I also make the speed bushings to fit.

So the stuffing tube only goes in the nose a slight amount?

[Chilli]

This is what I'm going to do Jeff. I have my first race in a two weeks and I want to try and get the boat in the water this weekend for a final test & tune. So for a temporary fix, I reamed out the bore so I have a little play between the shaft and the bushing. I made sure I have the play in both the front and the back of the strut. I'll order another wire drive through Steve since I also have to order another ESC. I'll make sure I still have good shaft clearance, make sure the strut is clean and free of any burs and grease the heck out of it. I'll do a test run as if I was trying out a new prop to make sure all is fine. In July I'll send you the strut and you can machine it out for a new bushing and make me a new bushing. The speedmaster strut bushing is way too long at 1-7/8 inch.

Here are the specs on the strut:
Strut without bushings is 1 inch long.
The Nose bullet adds another 7/16 inch.
The rear sleeve runs 3/8 inch into the back of the strut.
The bullet runs 1/4 inch into the front of the strut.
This leaves about a 3/8 inch gap between the front and rear bushing inside the strut.

For my setup, I have the stuffing tube 3/16 inch into the nose of the bullet and the front of the prop shaft about 1 inch into the rear of the strut? That leave me with 1/4" clearance between the shaft and stuffing tube and 1/4 inch contact area between the prop shaft and front bushing.

One concern. If you machine the strut for a bushing, is there going to be enough metal remaining on the bullet to keep it securely mounted to the strut. The wall thickness on the rear sleave is very roughley 1/64". I guess we'll cross that road when we get to it. I'll let you know how wire drive #2 goes this weekend.

Thanks for all your help!!!

[tylerm]

To help on race days, what you can do is modify the strut so its easily greasable.
You have a good setup to do this, so i think it could help you.

What you need to do is drill a 1.5mm hole(not sure what that is imperial) through the side of the strut where you have no bushings. This then allows you to use a grease gun with a needle point tip to re-grease the stub shaft between heats.

If you want i can take a photo of what im talking about and post it for you later.

Tyler.

[Chilli]

Thanks for the idea Tyler. I understand what your talking about, but go ahead and post a picture when you get a chance if it's not a problem. I take it that when you drill the hole on the side or high on the bore angled down, grease dosent blow out the ends of the strut when running.