Ok, I am digging around kit & aftermarket specs tonight -
i/ Tamiya says 87 links per track for their Mark IV.
ii/ Takom says 92 links per track for their Mark IVs.
iii/ Fruil provide 180 links in their standard set, equalling a possible 90 links per track.
Who is right? If anyone! Have all three manufacturers got such wildly different track pitches?
Seems to my vague recall that Grousers were often fitted on every 6th link, making a nice evenly spaced set of 15 per theoretical 90 link track. I know all sort of spacings did happen, either by design, carelessness, accident/damage, BUT it makes me err on the side on Fruil for correctness.
Thanks for any clarification.
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"You there on the port!". "S'gin actually, but thanks for noticing [hic]".
Ah, got it. The Haynes manual, makes a very scant reference to the number of links 180 in relation to 30 grousers, i.e. 15 each side - although the book also says tanks were issued with a compliment of 44 grousers each but they were seldom all fitted, with one incident of a crew getting cheesed off after 15 each side and lobbing the other 14 in a ditch/hedge!
So... Takom is closest kit-wise, but is it a typo in their instructions? They provide a total of 200 links BTW... so Gaza tanks with frontal track armour are possible!
I think I will e-mail Takom. They do answer questions!
I hope it is a typo, as shelling out for Fruil tracks and grouses would double the cost of each build!
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"You there on the port!". "S'gin actually, but thanks for noticing [hic]".
I don't know where, but I may have read that 89 was the correct figure - either that or my numerous track-link counting efforts concluded that rhomboids normally had 89 links per track; I know it doesn't quite work out nicely for a grouser at every sixth link, but that's the conclusion I reached.
Friul's other sets normally include at least a few extra links, so I doubt they would supply 180 if that was the exact number required.
As for Tamiya and Takom, having done many a calculation on the track pitch of various tanks (for future modelling purposes) and the effects of small increases or decreases in pitch, I can say that over 89 links it doesn't much discrepancy to add up to whole links difference. Assuming Tamiya and Takom have both measured their side armour accurately, it is quite likely that both have found it difficult to achieve the scale track pitch of 5.442857(etc)mm.
Over 89 links, that equates to a scale track length of 484.4mm, suggesting Tamiya's 87 link track has a pitch around 5.568mm, and Takom's 92 link track a pitch around 5.2654mm. Looking at other tank kits, it seems to be a big and quite understandable problem to get the pitch right at scale size - a tiny discrepancy that only a micrometer could detect (and even micrometers give varying readings depending on the pressure exerted) will add up to a sizeable gap or excess in track length.
So, if Friulmodel supplies 180 links, then presumably they must have a more accurate pitch than either Tamiya or Takom - it's just a shame that Friul's tracks are white metal, as I personally would much prefer plastic or resin links over ones containing lead.
My fruil set came with a total of 197 track pices. 23 more than necessary. This probably to supplement misscasts, shipping damage, builder error, and they probably weigh them out rather tan count them. A molders bonus.
...but Mr Fletcher is in agreement with Fruil's 180 links, as per my quote from the Haynes manual.
I have e-mailed Takom, and we will see what they say. The PMMS sprue photos are probably of the test-shot model, and things could change... esp as the release date is rumoured to now be September, instead of the original 17/7/2014, or HobbyLinkJapan's vague 'August'...
Clearly Takom have already found errata in their instructions and have addendums at the back to correct them.
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"You there on the port!". "S'gin actually, but thanks for noticing [hic]".
I've just done some link counting to double check: "Grit" at the Aussie War Memorial has 89 links in her snug-fitting right track, while the Mk IV formerly at APG has 90 links (and a frozen-in bit of slack above the front horn) in it's left track.
Conclusion? Look at photos, whether period or modern day, and you'll notice that some rhomboids have their idlers pushed further out than others on the adjusting screws - the gap created between the track and the radius of the side armour plate of the front horn is quite obvious; if the gap is present, your tank will have 90 links per track; if the track fits neatly around the horn without showing part of the idler, then the track will have 89 links.
It is my observation that Mk Is and many Mk IVs have snug-fitting tracks, and will therefore have 89 links per side. Mk Vs however, often have the idler pushed further out, suggesting the extra 90th link has been used.
Since 89 links is the correct number to fit neatly around the rhomboid shape, my guess is that an extra link was added to some tanks later on as a practical measure, since joining the ends of a track during maintenance would be easier with a larger gap between track and side armour, to access the track pins.
Since Tamiya and Friulmodel seem to need 87 links, and Takom 92, I suggest it's a bit academic: as long as you have tracks that fit, does it really matter if you have a couple of links too many/too few?
Although I will often say 90 links a side, in actual fact it is normally 89. Having said that, I wouldn't argue wit someone using 88 if it works for them.
One thing I found out when building the 1/6 scale MK1, is how little a variation in track pitch of each link, could make a significant change in track length.
To double check the gears and track 3D model before getting anything manufactured, I printed all the parts off on my Brother's MakerBot Printer. Long, long, long job, drove me mad, but worth it. To save time, I played with the quality settings when printing the large amount of track links required. Without realising it, this made a tiny difference in pitch of each link. Depending on how I mixed up the quality of links, I could get a difference of one link in length.
Soooo... yeah I'm getting to the point :)... as the track is cast on the real tanks, there is the possibility of the same tiny variation in pitch. Castings shrink, normally it is allowed for by making the mould a few percent larger, but variations will still happen.
Knowing also that they found a need to increase the amount of adjustment on the front tensioner wheel, when designing the MKIVs, casting variation and stretch (probably just pin wear) probably led some tanks to running with as little as 88 links a side.
Helen x
-- Edited by MK1 Nut on Wednesday 6th of August 2014 11:34:14 AM
Their kit does have 4 definite adjustment positions for the idler wheels though. I wonder if that, and overall take-up of slack, might allow for a possible 90 links as opposed to 92?
I'm sure it might be possible to gain a little track length from somewhere, without causing visible dimensional inaccuracies.
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"You there on the port!". "S'gin actually, but thanks for noticing [hic]".
My experience with 1/6th scale Armortek tanks, which use cast track links, is that they "stretch" after some usage.
Obviously they can't actually stretch, but the high points in the track pin holes wear away so that they effectively become longer.
Up to a certain point, this slack can be taken up with the idler adjustment, until that runs out of travel.
At that point, you wind the idler adjustment all the way from maximum to minimum and remove one track link.
So they may well have had 90 a side when fresh from the factory but, after a few miles travel and running in, had a link removed to make them 89 a side.
