Brian's 2017 NO. 10 LATE TIGER 1 BUILD

[Brian Ostlind]

Added one more board now I’ll ad the plates to the jack.

[Brian Ostlind]

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[Brian Ostlind]

[Tom OBrien]

Wow, brilliant work! It looks so nice, you will now have to stain the woodwork. Armortek should distribute your plans on their web site for anyone working 1/6 scale armor.

I got back my two idler axles and will install them tomorrow.

[sean kerambrun]

Hi guys,

This is me testing my custom tank bench




Cheers

Sean

[Brian Ostlind]

Hi Sean, thanks for posting your setup. looks good!

[Tom OBrien]

Guys, here's an email I sent to Kian describing my latest with the Tiger 1.

Kian,

I test drove my Late Tiger 1 after having moved the idler wheels inboard by 2mm. This solved the alignment issue and now the tracks don't "jump" or ride onto the top of the road wheels like they had been.

Also, I went from 92 tracks per side to 93 per side. With the idler adjusted to its maximum tension, the tracks rest about where they should on the road wheels. However, there is still a tendency for the tracks to come out of the drive sprockets when turning.

My next move will be to go back to 92 tracks per side, which I think should alleviate or even solve the 'track-jump off the drive sprockets issue'. But, I believe the tension/stress on the track train is excessive and will continue to result in tracks breaking whenever there is any solid debris (like granite stones over about 1/4 inch diameter) that rides up into the track guide channel (guide teeth).

Here's something new: On closer examination, it appears that the lack of height of the drive sprocket teeth may be an issue. I think that if you were to increase each tooth height by another 1.5mm-2.0mm, the tracks would be less inclined to jump. Can you model this?

cheers... Tom

END OF EMAIL

So, it may be that the drive sprockets could use a little modification before we have a correctly running tank. (My theory about the drive sprocket teeth height needs modeling and testing, if Armortek has the resources).

I understand there is expense involved but from a design and operational aspect, I hope Armortek can figure out how best to deal with it, if at all.


Tom

[Brian Ostlind]

Tom, great to hear you are working on the design. I thought about the tension but came to the conclusion that it is a Tank and it is strong enough! Best thing to do is avoid rocky terrain like Armortek advises.

Brian

[Tom OBrien]

I'm back to 92 tracks per side now. I'm charging it and will run it tomorrow to see how it goes.

Armortek' s got a great product and to their credit, they are keen to work with customers on issues like this. I may disassemble it over the winter to inspect and perhaps reinforce the suspension system, and to make sure it's perfectly aligned (there's no reason to believe it's come out of alignment but it can't hurt to check).

My problem as a retired engineer is this annoying habit of wanting to improve on things that are already good.

Also, it doesn't help that my first project out of grad school in the early 1980's was as an evaluator for the US Army's Abrams Main Battle Tank program. I have to take those glasses off and remind myself that this is a 1/6 scale WWII German tank, and not the Abrams.

cheers... Tom

[Tom OBrien]

Brian, Kian, et al,

Finally, after this morning's test it appears the running gear issue with tracks jumping may be solved.

Conditions: Outside temp is 25F. Snow covers much of the ground.

Tracks: 92 per side. The track tensioner/adjuster is set to about mid-way.

I've removed any washers (spacers) from the drive sprocket and road wheel axles that I had been experimenting with in my attempts to align the running gear. So, road wheels and drive sprocket are exactly where they should be per the instructions.

Chamfering: I re-chamfered the drive sprocket teeth according to Kian's suggestions, but not to the point where, like Brian's sprockets, they are like sharks teeth. (Note: I had re-chamfered earlier but this did not prevent the tracks from slipping off the sprocket teeth). Brian, I think you're OK but over a long period, you might want to replace the sprockets if you begin to see excessive wear at the front aspect of the teeth.

The last variable that seems to bring the running gear in proper alignment is the IDLER WHEEL. Visual inspection shows the idler wheels are now (nearly) perfectly centered when looking down along the road wheels. Earlier, I had removed 2mm from each axle, resulting in moving each wheel inboard (toward the hull). Also of note, the tracks still have at least 3-5mm clearance from the brass piece above the idler.

Operational Test: I ran the tank outside on smooth level concrete clear of snow backward, forward, and figure 8's for about 10 minutes. Then, drove it to a normally rough concrete pad with a slight down slope (about 5 degrees), backward, forward, etc. for another 5 minutes or so. Then, onto another part of the concrete with a steeper slope (about 10 degrees), same side slope driving. Speeds varied from slow to full.

There was NO TRACK SLIPPAGE during the entire time driving on concrete.

Next, I drove off the concrete onto gravel and into snow. I was careful to not pick up any gravel into the tracks. By now, the metal has cold soaked for about 20-25 minutes, so no apparent accumulation of snow/ice in the running gear.

I was able to pivot in the snow with NO TRACK SLIPPAGE.

I ended the test by driving full speed through the snow and back onto dry concrete, which cleared the tracks of any remaining snow.

I will continue to run it under varying conditions but from these preliminary tests, I would conclude that moving the idler wheel inboard brought the tracks into better alignment with the rest of the running gear, and hopefully it as eliminated any further issues with track slippage.

Sorry for the long winded post.

cheers... Tom

[Tom OBrien]

BTW, in my last post I forgot to mention I tested the tank with its turret and main gun barrel installed, so it was at its nominal operational weight.

Tom

[Brian Ostlind]

Sounds like you had a lot of fun out there Tom! Great to hear your tank is running well. We all customize the tank in some way or another it seems you have made a great modification. I am about to remove my tracks and re align some wheels that are still out of place from my driving. I am looking forward to getting the turret on as well.

[Christoffer Ahlfors]

There are two issues to manage when it comes to tracks. One is the sideways climbing of the sprocket. The other one slippage, skipping, cogging over. The latter can be cured with tightening the track and is caused by sprocket teeth out of shape OR stretched track that no longer fits the sprocket. A stretched track is the product of too tight tracks that either climbed the sprocket or got a stone or other object in the idler. The forces are enormous and can lead to breaking the track. This is why I always recommend track tension loose enough to allow climbing/slipping. Forget the "three finger rule" from the "tigerfibel" and protect your tracks instead!

The sideways climbing issue has to do with alignment. When everything is correct, the sprocket teeth should go in the middle of the holes in the track. That is, equal distance to the left and right. It is less than a millimeter, but it is important to know that it is not grinding against one side. When turning in difficult terrain, there will be sideways force on the roadwheels, especially the first and last ones. If the first wheels are not properly fixed, they will not assist in the alignment and the track may climb the sprocket. When fully correct, the track will still inevitably move slightly sideways and will reach the sides of the sprocket holes in the track. The side chamfer of the sprocket will assist in preventing climbing in this situation.

In all, I think there is no tracked vehicle that is immune to throwing a track, even on the prototype. Drivers simply learn to avoid the most dangerous situations. When the right tuning is reached, the model will be quite reliable and easy to drive, but there are situations when it will cog over or throw a track. This should be seldom enough not to be a concern.

I wish you both the best of luck with your tuning. And don't forget to celebrate when you are done!

[Brian Ostlind]

[Brian Ostlind]

Back pain is gone back to work.

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