The SdKfz 7 begins

[Andy Walker]

Im not sure what happens at this stage, at the moment the arms 0306 are not loktited in and can move. I am waiting to see what happens once the motion pack is installed. I personally don't like doing anything that cant be adjusted. I incidentally, there is not a lot of clearance between any of these parts and I ended up building up the bump stops to give a bit more.

Yes, i found that with the bump stops as well....I added a couple of washers under the rubber stop to raise them up a bit.

[Andy Walker]

Cracking on with the wheels. They seem to go on forever . I want to get the chassis assembled as soon as possible so that I can leave the heavy manoeuvring out of the way for a while, and concentrate on getting the motion / light/ sound packs tested and installed, and the tracks assembled. Got the dreaded Prostate Operation looming imminently, so could be taking it easy for a while. Oh the joys of getting older

[Andy Walker]

Just a tip that may save others a lot of head scratching. I have been fitting the main drive gears CG0119 into the drive casings today. I found that when I tightened up the Hex bolts securing the casings, both Gears were completely immobile...no rotation at all. By loosening the bolts a fraction, the gears turned perfectly.
It has taken a long day of head scratching ( and a few swear words ), but eventually I discovered that by sanding a small amount off the inside face of the recess that the bearing butts up to, on part CG1121 ( Outer Housing ), the Drive gears turn perfectly.
Luckily I hadn't already loctited the outer race of the bearing into the housing CG1121, otherwise it would have been a total disaster!
It may be that others don't have the same problem, but just in case it may be worth trying the above.
Happy building

[Andy Walker]

20250408_133653.jpg (177.46 KiB) Viewed 1533 times

One main drive gear and pinion fitted and running smoothly so far. Coated with dry moly lube. Other side fitted, but still working to get it as smooth as first one.

[Andy Walker]

Final coat of red primer on top of etch primer. Going to have to choose colour of topcoat now, before assembling anymore. Stuck between the yellow or grey....?

[Raj Gopaldas]

I have run into the same problem - the large gear not turning at all when the case is all the way tightened. After a day of troubleshooting, the problem in my build was narrowed down to the fact that I did not press the bearing all the way into the recess when I used the green Loctite 680. So removal was not an option - or rather not an easy option, I should say. So - I ended up using washers as a sandwich between each half of the case - for each screw when reassembling the case. So - yes - there is a gap in the case. I will use some type of silicone caulk to circumferentially seal the gap on the case. But they spin freely. My guidance to other builders system make sure that the bearings are pushed all the way into the recess when assembling the case, especially if using Loctite. Also, I would advise to dry fit the whole case first to make sure the gears spin before using Loctite. But that’s what makes building these kits fun!

[Jerry Carducci]

I have run into the same problem - the large gear not turning at all when the case is all the way tightened. After a day of troubleshooting, the problem in my build was narrowed down to the fact that I did not press the bearing all the way into the recess when I used the green Loctite 680. So removal was not an option - or rather not an easy option, I should say. So - I ended up using washers as a sandwich between each half of the case - for each screw when reassembling the case. So - yes - there is a gap in the case. I will use some type of silicone caulk to circumferentially seal the gap on the case. But they spin freely. My guidance to other builders system make sure that the bearings are pushed all the way into the recess when assembling the case, especially if using Loctite. Also, I would advise to dry fit the whole case first to make sure the gears spin before using Loctite. But that’s what makes building these kits fun!

Did you try a strong hot air gun to heat up the housing to soften the locktite? I would really try to remove the bearing. Putting washers as spacers to make up the bearing error is not an optimal solution. A hot air gun will not damage the surroundings or the bearing. If there's concern that bearing lubricant might be compromised it is possible to pry off one seal, repack the bearing and replace the seal. While it is annoying to have to do this it is, (in my opinion of course) better than leaving the bearing improperly positioned. That situation may have undesirable cascade effects later.

Jerry

[Andy Walker]

I have run into the same problem - the large gear not turning at all when the case is all the way tightened. After a day of troubleshooting, the problem in my build was narrowed down to the fact that I did not press the bearing all the way into the recess when I used the green Loctite 680. So removal was not an option - or rather not an easy option, I should say. So - I ended up using washers as a sandwich between each half of the case - for each screw when reassembling the case. So - yes - there is a gap in the case. I will use some type of silicone caulk to circumferentially seal the gap on the case. But they spin freely. My guidance to other builders system make sure that the bearings are pushed all the way into the recess when assembling the case, especially if using Loctite. Also, I would advise to dry fit the whole case first to make sure the gears spin before using Loctite. But that’s what makes building these kits fun!

I'm sure i fitted the inside bearings fully home, as I sanded the recesses to ensure this occurred. When I discovered the main gear wouldn't turn when the housings were tightened on, I did consider making a thin gasket to place between the two halves of the housing. However this would have been complicated and difficult to make. It was easier to sand the recess for the outer bearing, making it slightly deeper, to allow it slightly more room. This prevented the outer casing from squeezing it and stopping rotation of the main gear.
I agree that the whole assembly should be dry fitted fully before any loctite is used.

[Raj Gopaldas]

Valid input points indeed. I seriously considered removing the bearing, but the problem is I do not have a bearing puller at the location, I’m assembling it. I had to put the bearings in the freezer so that they would decrease in size a little bit before I could install them into the recess. So I was worried that heat might actually increase the bearing size and make it even tighter. I am new to building these kits and so there is a steep learning curve-nonetheless it makes it fun.

I do agree that there could be downside problems and I have been really pondering about this.

[Andy Walker]

Valid input points indeed. I seriously considered removing the bearing, but the problem is I do not have a bearing puller at the location, I’m assembling it. I had to put the bearings in the freezer so that they would decrease in size a little bit before I could install them into the recess. So I was worried that heat might actually increase the bearing size and make it even tighter. I am new to building these kits and so there is a steep learning curve-nonetheless it makes it fun.

I do agree that there could be downside problems and I have been really pondering about this.

Regarding fitting the bearings...I found lightly sanding each recess until the bearing just slipped in was a good method. Some required quite a bit of sanding, others barely any. Bearing loctite adhesive was then used to secure. The trouble with using the cooling method is that you risk the bearing getting stuck part way in if it heats up slightly while handling it, or if it only goes part way in and stops.

[Raj Gopaldas]

You are absolutely right about the cooling method because that actually happened to me on one of the bearings and what a nightmare it was to get it out. I’m not entirely a fan of the technique, but hey, I tried it and I learned from it.

[Jerry Carducci]

If the bearings are already such a snug fit, having to consider heating up/cooling down parts to allow them to fit then I'm wondering why loctite is even needed?? If a bearing needs that much effort to be seated in its mounting place then it should just be pressed into place. Once installed and it's secure under operational loads it should be fine with no slippage.

Am I missing something?

Jerry

[Andy Walker]

If the bearings are already such a snug fit, having to consider heating up/cooling down parts to allow them to fit then I'm wondering why loctite is even needed?? If a bearing needs that much effort to be seated in its mounting place then it should just be pressed into place. Once installed and it's secure under operational loads it should be fine with no slippage.

Am I missing something?

Jerry

The trouble is the majority of the the bearings wont go in to their recess as supplied, and if force is used they usually only go in part way, and then stick solid. I've found the most reliable way is to evenly sand around the inside face of the recess, and clean and check regularly to see if the bearing will gently push into the recess. With care you can get it to where the bearing will stay put if tipped upside down, but will fall out with a few gentle taps. I've tried the forcing method before, and it didn't end well...lol.

[Jerry Carducci]

If the bearings are already such a snug fit, having to consider heating up/cooling down parts to allow them to fit then I'm wondering why loctite is even needed?? If a bearing needs that much effort to be seated in its mounting place then it should just be pressed into place. Once installed and it's secure under operational loads it should be fine with no slippage.

Am I missing something?

Jerry

The trouble is the majority of the the bearings wont go in to their recess as supplied, and if force is used they usually only go in part way, and then stick solid. I've found the most reliable way is to evenly sand around the inside face of the recess, and clean and check regularly to see if the bearing will gently push into the recess. With care you can get it to where the bearing will stay put if tipped upside down, but will fall out with a few gentle taps. I've tried the forcing method before, and it didn't end well...lol.

I'm probably spoiled, I have both arbor and hydraulic presses to press bearings in place. That said I have yet to find a need to use them assembling these models; if anything I've found those in my kits to be quite the loose fit.

I also found that having an internal bearing puller is a comfort in addressing the odd bearing that refuses to play cricket..

Jerry

[Armortek]

With regards to the bearings, the tolerances are machined to be quite tight - so with that in mind, if a bearing cannot go on to a shaft or into its seated position then:
1. Make sure that any burr or turned in edges on the mating part is removed. We saw this in a earlier thread with regards to not being able to get a bearing onto a drive shaft - the reason was burr on the drive shaft.
Keep in mind that all aluminium parts get put through a process to remove sharp edges - this in turn may result in edges being turned in and needing a clean up before a bearing will fit.
2. The bearing must be placed square onto the matting part - if it at a slight angle it may look/feel like it should fit, but it will not.