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Tracks and Chain Tensioning

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1 Tracks and Chain Tensioning
Distributor Conference 2006 Workshop Good afternoon ladies and gentlemen. Welcome. How do you like the conference so far? Thank you for coming from near and far to see our new product offerings and learn new things about marketing and distributing the product. It is an opportunity for us to present new information and share ways that we will address some issues. I am Brian Cressman. I’ve been R&D manager at ODG for over 12 years, since the early days of the Conquest. Today, along with Peter Visscher, I hope to share what we have learned about rubber track use on the Avenger vehicles.

2 Tracks and Chain Tensioning
Background Installation of rubber tracks Research Goals Variables Results Conclusions/Recommendations I will present briefly, on the background of tracks and chain tensioners at ODG and then Peter will present his work on the tracks, with our conclusions and recommendations.

3 Background info: Chain Tensioners
1996 R&D work on new tensioner 1997 Introduction of tensioner on Bigfoot (new model Argo) 1998 Migrated up and down to all Argo models, Vanguard through Conquest 2003 Avenger intro. to Distributors 2004 Avenger manufacturing startup end of January

4 Background info: Chain tensioner features/benefits:
·   Semi-automatically adjust to new “fixed” position ·   Extends chain life 2 to 3 times by taking up more “stretch” before touching the frame and also reduces shock loading ·   Eliminates chain tensioner “slap” on floor pan during turns ·   Eliminates vehicle lurching during turning caused by stretched out chains


6 Background info: Tensioners currently used on:
Avenger EFI, Avenger, Response, Frontier, Vanguard 2, Vanguard All models since 1998 (’97 for Bigfoot)

7 Background info: Tracks:
Since early ’80s as plastic segmented track Rubber tracks were desired for increased wear/life/traction 2000 – Centaur All-Season Tracks and Winter Tracks developed and introduced

8 Background info: Tracks:
2004, Jan. – June Development of rubber tracks for Avenger 2004, September Introduction of track kit 2005, Jan. – Mar. Testing/evaluation of tire sizing and track tension 2005, April 4 First Hinge Kits c/w Extensions sold

9 Background info: Some problems (symptoms):
Worn tensioner blocks and damaged components Premature bearing and flange failures Broken axle hubs

10 Background info: Definitions:
Chain wear Chain stretch Chain windup Forward loading Reverse loading Over-tensioning

11 Installation of Rubber Tracks
(Things your mother never told you.) Good morning. My name is Peter Visscher. I’ve been doing research with ODG since the beginning of May, mostly on this topic. My background includes 7-8 years as a snowmobile mechanic as well as the past 5 years working with track drive suspensions.

12 Research 700 lbs of iron 223 lbs of driver 200 meters of dry pavement
110 tests 16 tires 2 rubber tracks 1 unfortunate Avenger This research project lasted 2-3 months and stole the innocence of an Avenger. These were the toughest conditions that a track could be operated on.

13 Goals Eliminate reverse loading Reduce chain tension
Avoid track walk-off Maintain traction There were 4 main goals to achieve: Eliminate reverse loading: Whenever the chain is tight on the “wrong” side, the tensioner slider blocks will wear rapidly. This is a result from a wheel being “pushed” along rather than pushing. Reduce chain tension: The other kind of chain windup is increased chain tension on the working side of the chain. If this can be reduced, the life of the chains, bearings and sprockets will be increased. Avoid track walk-off: The operator should arrive back from an outing with both tracks still on. Maintain traction: The wheels should not slip within the track.

14 Variables Tire size Tire pressure Track length Tire direction
There are a few variables that can be controlled on our journey to driveline happiness. Tire size (circumference) varies by up to 2” from the smallest tire to the largest tire. Tire pressure also has a big impact on effective tire size. Additionally, the length of the track can be adjusted by adding or removing hinge kits and/or track extension. Finally, the tread direction on the tires can be reversed by moving tires to the opposite side of the machine.

15 Chain tension tester was constructed using a load cell
Tester was mounted onto the frame of an Avenger Before we can reduce reduce driveline loads, we had to measure them. I used a load cell connected to an idler sprocket and a bit of trigonometry to get an actual value for chain tension while driving. These loads were recorded using a data logger. The apparatus was designed to fit in two locations: the idler chain that drives the rear 3 wheels (as shown) and the rearmost chain.

16 Free-wheel hubs Iron weights Track Extensions
Several other tools were used. The free-wheel hubs allowed me to “disconnect” any tire from the driveline, effectively isolating the remaining tires. This provides a clear picture what each tire is doing. Iron weights were added or removed to simulate real world (although extreme) use. Finally, hinge kits and track extensions enabled me to lengthen or shorten the tracks, allowing me to explore the effect of varying track tension.

17 Test route: Drive 100 meters, turn around, and drive 100 meters back.
This is a typical graph from two test runs with identical setups. The chain loads shown are taken from the chain that runs from the idler shaft to the second axle, driving the rear 3 wheels. The large spike in the middle shows how high the chain loads go during a full 180 degree turn. The smaller spikes represent steering corrections. Although they do not occur at the same points in the test run, the magnitudes are equal. The part of the graph of greatest interest to me is the Steady-State chain loads. This is where chain wind-up and rapid driveline wear can occur. In these test runs, the steady state chain loads are around 600 lbs for the second half of the graph (a good number).

18 Effect of small variations in tire size with a tight track:
Blue: Front tire is virtually the same size as the rear tire Red: Front tire is smaller than rear tire Green: Rear tire is smaller than front tire This graph shows what can happen with a tight track. These results are from 3 successive test runs in which the sizes of the front and rear tires were changed slightly. The first run (blue) has front and rear tires that are almost the same size. Some windup is evident as the SS chain loads rise to 800 lbs. Next, the front tire was reduced from 7 to 3 psi. The red line shows dramatically higher chain loads as the larger rear wheel is forced to do all of the work. Since the SS chain loads are over 1300 lbs near the end (and it requires only 600 lbs to move the vehicle), it is clear that the front chain is experiencing about 700 lbs of reverse loading. This will wear the slider block out quickly. For the green test, the rear wheel was made smaller than the front tire (7 psi front, 3 psi back). Although the graph shows zero chain loads, it is actually a negative number, as the chain going to the rear is now experiencing reverse loading. This causes rapid wear on the rear slider blocks. This is all due to small variations in tire size. Tight tracks = Chain wind-up

19 Effect of small variations in tire size with a loose track:
These are the same tests as the previous slide The track has been lengthened by 2” This set of three runs is identical to the previous slide except for one thing: the track has been lengthened by only 2”. Although there is some variation in chain loads as the tires size was changed, the difference is minor and there is no reverse loading anywhere. Loose tracks = Lower chain loads

20 Effect of adding/removing cargo (tight track):
Blue: with 700 lbs Red: weight removed Tight tracks = High drive train wear Adding or removing cargo can make a big difference on chain loads, but not exactly as you might expect. The red line represents an unloaded Avenger, while the blue line represents a loaded one. Although the peak loads are lower (as might be expected), the SS chain loads are considerably higher. This is because when the weight is removed from the back of the vehicle, the rear tires grow a little, causing them to do all of the work. The high SS chain loads (red) indicate high wear on the front blocks and rear chains/bearings. This over-sensitivity is unacceptable on a machine like the Avenger.

21 Effect of adding/removing cargo (loose track):
Blue: with 700 lbs Red: weight removed Loose tracks = Happy drive train The same tests were repeated with a 2” longer track. Although there is a bit of a difference, both test runs returned acceptable runs.

22 Measured tire size vs. actual tire size
Red: Measured size Blue: Actual size on Argo (unloaded) Yellow: Actual size on Argo (loaded) Tire sizing can play an important role as well. We performed some rolling tests to compare the measured circumference with the effective circumference. The red blocks show the measured size of the tires. (explain sizing order). When installed and measured on an empty Avenger, the middle tire shrank the most while the rear tire was unaffected. You can actually see the banana frame shape on the blue and yellow graphs. When loaded, the rear tire shrank while the front tire actually grew. Placing the largest tires on the middle axle helps to compensate for the difference in effective size. Measured size is not the same as effective size!

23 Effect of tire tread direction on rear chain load:
Red: Tires mounted in standard direction Blue: Tires mounted in reverse direction Reversed middle tires = lower chain loads Tire direction is the final tool we have to play with. These two test runs were identical save for the installation direction of the middle tires. The lower chain tension (blue) is a result of the middle tires being installed “backwards” … or “properly” if you’re from a farm. Because of the shape of the tread, it is easier to deflect in one direction than the other.

24 Recommendations: For rubber track installation on the Argo Avenger:
Inflate all tires to 5 psi. Measure and record all tire circumferences. Install tires as shown in chart. Deflate end tires and install track. Inflate tires as shown in chart.

25 Recommendations:

26 Recommendations Track Length: 235” total
Track Sag: 2-3” under middle wheels

27 Conclusion: Questions? Reduced chain loads No reverse loading
Longer lasting chains, bearings and sprockets No chain over-tensioning No reverse loading Greatly reduced wear on slider blocks Better drive efficiency Questions?

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