TRA turbo arm weight

turbo800 · Feb 8, 2014

I'm curious why you decide to add so much weight (6.1g) when you said your setup was really close and only needed a little bit?

I thought I had threaded pins, turns out, I have hollow pins. Gotta do something there!

The bolts that thread into my TS arms have short threads, I wasn't able to add the weight(washers)where I wanted to. I thought about adding weight on the opposite side (roller) but thought there might be a chance it would hit the ramp at some point! With the provided set screws(1/4-28) coming from the backside, I was able to get up to 76 grams.

Nearest I can tell from the #'s, your Etec @ 8psi and my HO @ 10psi, make about the same HP...

Backcountrypro · Feb 8, 2014

I added the weight per Tom's recommendation. I added more wieght because I am only running on clicker two. I would like to turn the boost up to 10 lbs and without more weight I would be on the rev limiter on clicker one. I know 6 grams sounds like a lot but the closer you move the weight to the pivot point of the arm the less effect the weight has. I am thinking this will be really close. If not I have lighter weights I can install.

turbo800 · Feb 18, 2014

I was able to get out and test the new clutch setup a little bit Saturday. I like it alot! I loaded it down with 78g arm weight with "narrow" solid pins. It was holding 8000 rpm on clicker 3, but I had an obvious boost leak, only making 3psi @ 9K' elevation. Got that fixed yesterday!

This is my current weight setup:
Bare TS arm w/roller & cotter pin: 48.6g
Bottom Hole: 4.6g
Top Hole: 8.1g
Solid Pin: 16.7g
Total: 78g

Backcountrypro · Feb 18, 2014

Glad it is working good for you. I just got back from another three day ride in some of the deepest and wettest snow I have ever rode in. I ended up running in clicker 5 with my set up which is higher than I would like. I guess that 6 gram weight will be coming off and something lighter will be going in its place. I turned the boost up to 10 lbs and it worked very well. I know I was a little rich on my fuel and the heavy snow took some serious HP but I was still very happy with how the sled worked.

turbo800 · Feb 23, 2014

This weekend I went out for another round of testing. Boost leak fixed making 8lbs boost w/o the boost controller.

Snow conditions were firm with a couple inches of fluff on top. I was hitting the rev limiter at 8400. Clicked down from 3 to 1. No change. Changed the helix on the hill to the 48* side, no change.

I can't decide whether to go to a softer finish rate spring or try to add more weight to the arm somewhere. If I did add more weight, it would likely have to be on the ramp side of the arm! A third option is a flatter finish ramp

tinman800 · Feb 23, 2014

What primary spring u running? You could try a softer secondary spring that would allow quicker upshift, just have to watch out for excess slip in the secondary.

turbo800 · Feb 24, 2014

tinman800 said:
What primary spring u running? You could try a softer secondary spring that would allow quicker upshift, just have to watch out for excess slip in the secondary.

Its noted above, also the same as Backcountrypro's setup, a 160-290 (Purple/Blue). Engages about 3600 rpm.

I think I gonna make some "wide" solid pins, and a lower finish rate primary spring.

turbo800 · Feb 26, 2014

Some new custom pins I machined to try, going from 16.7g to 21.7g (+5g) pins. Stainless OD, Brass ID:

I want to up my engagement slightly so I'm gonna try going from the 160 to a 200 start rate. I'm surprised how little options there is out there for anything in between. There were 4 I did find, BRP 185-410, Dalton 180-355, Goodwin 190-410, STM 190-280.

Backcountrypro · Feb 26, 2014

I would go for that 180-290. I like the looks of your set up. Sounds like you are getting close to dialed in. I have my last trip of the season coming up and hopefully I will have the clutching spot on.

BOHICA · Feb 26, 2014

Here's a few more spring options.
http://www.speedwerxstore.com/index.php?l=product_detail&p=872

turbo800 · Feb 27, 2014

BOHICA said:
Here's a few more spring options.
http://www.speedwerxstore.com/index.php?l=product_detail&p=872

I looked at the Speedwerx springs, they don't offer anything in between the 160 and 200 starting rates either.

turbo800 · Feb 28, 2014

turbo800 said:
Some new custom pins I machined to try, going from 16.7g to 21.7g (+5g) pins. Stainless OD, Brass ID:

I want to up my engagement slightly so I'm gonna try going from the 160 to a 200 start rate. I'm surprised how little options there is out there for anything in between. There were 4 I did find, BRP 185-410, Dalton 180-355, Goodwin 190-410, STM 190-280.

Backcountrypro said:
I would go for that 180-290. I like the looks of your set up. Sounds like you are getting close to dialed in. I have my last trip of the season coming up and hopefully I will have the clutching spot on.

I have a BRP 200-290 (Green/Blue) I'm gonna try out next ride, going up on the engagement slightly and keep the finish the same for now. I found a pin hole sized leak in my heated carb line that was spraying anti-freeze onto the clutches. Probably why I was hitting the rev limiter last ride. Got that fixed!!

I'm gonna leave the 78g arm weight alone, one thing at a time! If it still needs more weight, I'll put the heavy pins in later. But I am gonna try the reverse 44-48 helix out though.

Side note,there is a pretty good thread in the turbo Poo section on their clutching setups. General consensus, 74-78g flyweights. One other thing notable, going to big angle helix's need a heavier finish rate secondary spring (~300) to keep the belt from being drug through the secondary clutch.

Backcountrypro · Mar 9, 2014

OK I think I am done riding for the season. Here is what I learned in regards to TRA arm weight. I started out with Tom's arms loaded up to 78.0 grams, 160-290 spring, 44 helix with a heavier XP secondary spring. I should have left everything right here. I added 6 more grams down low on the arm thinking that if I one day decided to increase the boost I would need additional weight. Six grams was too much so the next trip I stepped down to roughly 3 grams added over the initial 78.0 and I turned the boost up to 10 lbs. What I found is that as the load increased even at the higher boost level I had to increase my clicker position higher and higher. I ended up running on clicker 5 and could have possibly gone to clicker 6. My thought is that at the higher boost levels the engine was producing higher track speeds and you come to a point where the engine cannot pull anymore weight, I guess you could call this "breaking its back". On hard pack snow this set up would work as you would come to a point where the clutches are fully shifted out. What I found in the deep powder was in cases where at the end of the climb where the motor is pulling as hard as it can if you begin to loose any RPM the engine would begin to go rich. Looking down at my gauges I could watch my RPM's begin to drop and the AFR heading for rich, all the while the boost gauge is right on 10 lbs. The fuel controller still sees 10 lbs of boost but with the slight reduction in RPM the motor is not able to burn all this fuel and it will start to run rich.

What I learned from this is you have to clutch the sled with the right amount of weight so under the heaviest load the RPMS stay right at 7800-7900. My theory is when clutched right the engine will seem too lightly loaded for hard pack conditions but heading into a steep/deep climb the RPMs will settle right in on that sweet spot with out moving regardless to the load. Too much weight and the sled will not be able to recover. For next season I will be throwing in a new 160-290 spring and I will go back to my original 78.0 grams.

worx53 · Mar 10, 2014

arm weight

some thoughts. adding weight in the tip will be better than anywhere lower in the arm to control wfo rpm when adding a few lbs. of boost.
For instance a 20 hp change can usually be compensated by one to two grams of pin weight in the tip. If your setup is close, (bc pro) than adding the weight in the bottom where the turbo has the least affect (not making big power) will load it way too much early in the shift and it will be really lazy and still pull rpm down a little at wfo as you see it had to run in clicker #5.

turbo800 · Mar 10, 2014

BCP, I'm curious why your done for the season? Our snow is great finally, came VERY late in the season!

Got to test out my setup Saturday. Running 10# boost, had to click down to 1 to stay off the rev limiter (barely). Going from the 160 to the 200 engagement went from 3600 to 3800. I definitely like the higher engagement. I wouldn't even mind a 4000 engagement, but there isn't a spring with the same finish rate I need.

I figure I have two options from here:
1- Go to a lower finish rate spring (160-260 or 160-230) and lose my higher engagement.

or

2-Install my heavy pins and push the arm weight up to 83 grams.

I think I'm gonna try option 2 next

Backcountrypro · Mar 10, 2014

I wish I wasn't done but it's time to get back to work.

Backcountrypro · Mar 15, 2014

Well I guess I am not done yet.....going to head out to Montana late next week for the final ride. Here is the bad news.....I am going to start all over with my clutching and gearing. I think my current set up of gearing and clutching is leaving a lot on the table.

swrev · Mar 17, 2014

Changed my gear ratio to 2.14 and pulled 103 mph on the trail, backed out as the egt's were starting to creep up also. Pulled a little over 70 climbing and was still gaining at the top, hard pack hill mostly; same hill a year ago was about 10 mph slower. Doesn't feel like I gave up anything boondocking. Gearing up, also eliminated much of the zingy or revvy feel my sled had.

simbatheking · Feb 4, 2015

I just went to a 2mm over roller as DJ recommended to make it more snappy on bottom end. It's 3g heavier and I only dropped 1g because before I was over revving a bit. Now the sled jumps to 8000 rpm from a stop right away in powder but then bogs and falls on its face right away. If I gradually accelerate in pow to about 1/2 throttle it falls on its face too. If I punch it on the trail it pulls hard but that's not really a good test since it gets going too fast to tell much on trail so I can't hold it wfo for more than a couple sec. I'm not sure if the issue is the big roller or 2g more flyweight. Before the clutching felt almost perfect but I wanted to more revy on bottom end.
Old setup
2.25 track
21/49
160/290 prim
20 g pin
413 ramp
Shockwave backed out almost all the way
Purp sec spring
Clicker 3
Stock roller

Current setup that doesn't work
3" track 7t
21/49
160/290
19g pin
415 ramp
Shockwave tried in all positions and makes still has issues turned in all the way
Purp sec spring
Tried all clickers and still falls on its face when u pin it
2mm over roller

worx53 · Feb 8, 2015

put a set of hrss1 ramps in it and run 1.5 grams less pin weight with setup #1. it will be about perfect

TRA turbo arm weight

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