I'm Replacing the Roadwheel Bushings with Needle Bearings

[Mike Conley]

Hi all! I bought my Sd Kfz 7 halftrack used a couple years ago and I've noticed how the inner roadwheels 'wobbled' a LOT! The bushings were so worn out on the axles that the wheels could travel wherever they wanted to go and even LEAN. Since the middle wheels guide the track horns that ain't good. The tracks weren't being held inline and so the horns kept wanting to climb out of the sprocket holes.

The bushings for the wide wheels and the six inside middle wheels are 10x14x12mm and the six outside middle roadwheels are 10x14x8mm. I seached to see if there's any SEALED bearings but the closest I could find were 10x15x4mm so I would have had to use 3 bearings to make up the 12mm length AND I didn't want to have to bore out the diameter of the hubs. SO, I ordered some 10x14x12 needle bearings and they fit PERFECT! I would have prefered SEALED but 'Whatta ya gonna do'... I just won't drive this 7 out in my sand pit anymore... and it prefers grass or pavement anyway.

No one makes 10x14x8mm needle bearings so I ordered 10x14x10mm ones for the six outside middle wheels. When they get here I'll see IF either I can use a longer screw and spacer to move the outside washer OUT and still get the hubcap on or if I'll have to cut out 2mm in to the inside back of the hub so they'll fit. It's pretty THICK back there so 2mm wouldn't hurt anything.

With the needle bearings the wheels spin so EASILY and they're SOLID with no wobble! You put'em on the axles, give'em a SPIN and they keep spinning 'FOREVER'! A LOT less drag!! I'll let you know what I figure out on these shorter needle bearings when they get here.

Mike in Kentucky

[Mike Conley]

Okay, I received the 10mm long bearings and here's some pictures. When I had them side by side, I measured them and the length difference is about 1.85mm between'em.

I installed the keeper screw and (thrust) washer and I knew it would touch against the washer but I wanted to see if the hubcap would go on and it 97% will.

I measured the thickness at the rear of the hub and it's about 6.32mm back there so taking out almost 2mm shouldn't hurt the strength, especially with 1.85mm MORE bearing on the axle.

I'm using my small Smithy lathe to SLOWLY cut deeper back in to the hub. I AM NOT a 'machinist' in ANY WAY! My old, loose lathe ain't what you'd call 'exact' (and NEITHER AM I) BUT I'm giving it a good try. I've got the three outside inner wheels done and tomorrow I'll putting'em on, turn the 7 around and do the other side. I don't want to rush this precision job and mess it up SO right now it's 'O-BEEER-THIRTY!'

Mike

[Christian Steinhauer]

Hello Mike,

you should take other bearings, needle bearings for the wheels isn't a good solution on my opinion.

[Mike Conley]

Hi Christian!

Well, I seriously thought about getting 10x15x4 SEALED bearings and they ARE pretty 'cheap' ($1 each) but then I would have had to bore the hubs out to 15mm. Though the cheap cost of three bearings per one bushing I would have been happy to pay. I could not find any 10x14x4mm sealed bearings to do five per wheel.

Those axles are HARD steel and the hubs are aluminum. If greased needle bearings hurt the axles then it's time for new roadwheels and axles.

I could have just bought new bushings I guess but I like to try and find the 'New & Improved' options. IF these needle bearings don't work out I'll get new bushings. But as WORN OUT as the insides of the hubs are, that wouldn't make much difference.

If I have any 'trouble' in the future I'll proudly post it on here to share information between owners. Heck, if I DO have any problems I'm sure it'll be the loose hubs anyway.

The only two Armortek vehicles I have that DON'T use bearings is the 7 and the Sherman... but I kinda LIKE the way the Sherman SQUEEKS!!!

Thanks Christian!!

Mike

[Mike Conley]

I know of a GREAT tank builder and machinist who mentioned that it would be better if I could have made new bushings out of material that doesn't need lubrication, and I totally agree. I thought he was referring to nylon (which I like) but he said there's better bushing stuff like Delrin, Acetal, PEEK, and HDPE but he may as well been taking Klingon to me.

And, as I mentioned, I am NOT a machinist! Can barely SPELL 'machinist' (had to look it up!) I know lube is a 'bad thing' where dirt, sand, grim, etc., and get to it. But I don't know how to cut, drill, make bushings out of that stuff.

So needle bearings is what I'm going to try out for now. With the condition of these bushing and hubs, what can it hurt?

Mike

[Christian Steinhauer]

Mike,

if you want needle bushes you need some with inner rings. If you have a look on your picture, you can see that a screw will tighten the needle bearing to the axle. Also the forces from screw will hurt he outer cage of your needle bearings. That will stop or slow down the wheel on the axle. Further more you
need a kind of sealing on both sides of the bearing for water and dirt, if you want to do it right.



Best solution for axle-wheel conections are ball bearings or tapered roller bearings. But for those you have to expand the hole on the wheels and/or reduce the diameter of the axle, as you mentioned. I would prefer ball bearings ZZ (with plates) for your wheels.
Don't you have a metal workshop with a lathe nearby?

[Mike Conley]

Hi Christian!

That photo was to show how MUCH material had to be removed in the back of the hub so the 10mm long bearings WOULD fit in. I've been using my lathe to do that. I've been removing a little at a time (about 1.85mm) then installing the bearing, putting it on the axle to make sure the bearing is far enough BACK behind the end of the axle so the screw/washer won't squeeze it.

As I mentioned earlier, this old lathe isn't the most accurate AND I am NOT a machinist but it's turning out pretty good. I've gotten one side done, drove the 7 out to turn it around, then drove it back up on the lift and it seemed to run fine on the bearing side.

If later I decide to go back to bushings I can order some AND the 6 outside middle wheels will already be bored out for 10mm long bushings instead of the original 8mm.

Thanks for pointing out that bearing going past the end of the axle!

Mike

[Robert E Morey]

Mike,
That should do the trick nicely! Glad your are making progress.
Bob

[Mike Conley]

Thanks Bob! Wish I had YOUR AMAZING skill as a Machinist! I do good not to loose my fingers (so far!)

I would have finished the last three outer middle wheels today BUT we spent most of the day canning green beans and bananna peppers out of the garden. I'm COVERED UP (15.5 QUARTS) with bananna peppers! Half of the jars are 'cold canned' (MY favorite!) and half are the 'old style' hot canned (which last longer!) So for the next year I better eat a LOT of peppers!

And FYI: something I forgot to mention, after I installed the needle bearings on the left side of this 7, when I took it out to turn it around in a big 'U' turn in my driveway, I saw it kept wanting to pull to the RIGHT. Since I'm used to it tracking straight, I thought 'NOW what's wrong?' then I realized the right had more resistance because of the bushing drag! It was noticable but it took me a few seconds to realize that was what was causing it! I had to compensate with steering until I got it back in.

And I just read on the Sherman site that a while ago someone found that needle bearings could be installed in the Sherman roadwheels! I'll think about possibly doing that much later because, as I mentioned, I LIKE the SQUEEEKS of the M4A3!!! It SOUNDS like a TANK!

Mike (I'll let ya know how the bearings do when I git'er done soon!)

[Adrian Harris]

> I LIKE the SQUEEEKS of the M4A3!!! It SOUNDS like a TANK!

I think that's pretty much all track noise, as the Sherman runs with the tracks tighter than any other Armortek model.

I've been following your progress as I'm doing up a 7 at the moment, and the bushes were in a right old state when I got them out of the wheels.

Adrian.

[Mike Conley]

Hi Adrian!

What prompted me try these needle bearings (besides NOT being able to find SEALED bearings) was the inside roadwheels were so loose. When I pulled all the wheels off, some of the inside bushings STAYED ON the axles. The wheel hubs were spinning AROUND the bushings instead of the bushing spinning around the axles! As I said, this 7 was USED before I got it, now I'm trying to make it roll better.

I have my sand area out back (that my wife ordered 25 tons of sand JUST for the tanks) and the tanks like it but this 7 isn't a 'big fan'. I prefer to run the 7 around the lawn or driveway so grit and water shouldn't be too big of a problem.

The 10x14x12mm (and 10mm long) bearings I found on ebay for about $6 for ten bearings (12MM) so I ordered three sets and one set of 10mms so I'll have extras.

I'll probably finish the other side tomorrow (unless SOMETHING ELSE comes up around here! i.e.: wife projects!) and I'll take it out for a drive. I'll let ya know how it does or if there's any problems!

Mike

[Robert E Morey]

Mike,
Those peppers are making my mouth water - sounds so good!

That's a good wife - to order you some play sand! Awesome!

The only downside to the needle bearing <after the custom machining/fitting> will be they won't like dirt. I don't know if the back of the axle <hull side> are sealed? Fine grit and dirt will work its way into the needle rollers and eventually gum them up. But they should roll much better than the bushing. The front side of the bearing should be sealed once the hub cap is back on.

I looked on my bearing sites as well and found no shielded ball bearing in 10mm ID X 14mm OD x 4mm thick <15mm OD yes>. So I think you found the best solution.
Bob.

[Pete Nash]

Hi Mike

I hope you don't mind my two cents worth.

The bushing material your friend might have been thinking of could be Phosphor-Bronze. This alloy has a number of uses because of it resistance to wear and corrosion, and to some extent has self lubricating properties.

That well known internet based auction/selling site has it for sale, here in the UK its about $50 for a 1" diameter 12" length.

You say you aren't a 'machinist', if you can get down to 1.85mm accuracy I'd say you are well on the way to being one

Regards

Pete

[Mike Conley]

I MESSED UP THIS MORNING!!! This morning, bright and early, I headed out to the garage to finish boring these last three outer middle wheels. Turned on the radio to the 'Classic Rock' station and went to work. I picked up the first wheel to bore with A needle bearing that was sitting beside it. Put the wheel in the lathe and bored some. Took it out, pushed the bearing in, put the wheel on the axle and saw I had more to bore out. Bored, checked, more to bore out. Bored, checked, just a little more to bore out. Last check had it PERFECT!

THEN tapped the bearing out and suddenly noticed, I HAD BEEN USING A 12MM LONG BEARING TO CHECK IT!!! I thought I was using a 10mm bearing! Any of you in other countries 'may' have faintly heard some VERY NAUGHTY WORDS in the air right then!!

Worried, I measured the rear of the hub for thickness and 4.81mm of hub was left on the back. Still thick enough... I bored the other two hubs at 10mm... and the 12mm hole seems to work okay.

I put the wheels on, realigned the sprockets, and took it out for a drive and this 7 seems HAPPY! There's still some 'chatter' when I turn but about half as much. There's still three middle outside wheels (on the OTHER side) that are kind of 'loose' but, again not as much. That's because even though the bearings run on the axles PERFECTLY, the inside of those hubs are 'wollered' out. The other side is a LOT tighter with less wobbling but spin so easy.

It seems 'snappier' and does have MORE speed to it as I'm walking beside it. AND, the wheel that I 'messed up' on and now has the 12mm bearing in it, IT has hardly ANY wobble to it! I guess the 4mm longer hole gave the bearing more hub to rest on. If I would have realized THAT, I would have bored the other FIVE outside middle wheels out too to 12mm deep!

I'm VERY HAPPY with the way this 7 runs now! In a few years (IF I'm still around then because I'm 62) I'll probably upgrade again with some of those solid bushings you all have been telling about. But 'I'M NOT A MACHINIST' so making 24 of those bushing that matched would be a miracle.

Thanks Everyone for the advice and when I go to install bushings made out of the material you told me about. We'll see how well these bearings hold up till then. THANKS AGAIN!
Mike

[Vince Cutajar]

Job well done Mike.

Vince