No.36 251 in the tropics

[Eric Ho]

I got number 36! Thanks to the previous posts (especially Dennis'). I've taken the plunge into my 251. I've also ordered a set of rivet squeezers, hopefully it would make less work on the riveting section.

River squeezer

Deburr and degrease

Metal prime and paint prime

[Dennis Jones]

Hi Eric,

Glad to hear you have made a start, not sure how you will get on with the rivetting tool as some of the areas are very difficult to get in to because of the angles. Anyway keep us up to date with the progress.

Dennis.

[Eric Ho]

Thanks Dennis, yes I've studied the angles and joints and will only perhaps be able to reach 60-70% of the the rivets even with the deeper jaw option. There will be some that will have to use the good old fashioned method described in the manual. It's also mainly to keep the noise down (esp on weekends).

And then there's still the sequence to keep in mind (thanks for that tip!).

[Eric Ho]

More fitting to be done, it's down to the smallest gap in the differential housing. The housings close nicely without the differential inside, it's the bearing seats that seem to need some work on.

Almost closed!

The other drive parts fit perfectly after deburring, the shafts and bearings are the perfect interference fit with the right alignment and very little tapping in. Trying to make sure any binding or friction is eliminated at this point for a smooth drive in the end.

[Eric Ho]

A bit more work done, adjusting, adjusting....first the steering tie rods and making sure the ball ends don't foul.

Steering adjust

Steering 2

Next were the torsion bar installation and more adjustments.

Torsion bar setup

[Dennis Jones]

Hi Eric,

Glad to see progress. One thing I did notice however is the track rod should be below the tie rods not above as you have put it (see photo on page 3 of my post). It is shown in the manual as on top but having discussed it with Mark there is more clearance if mounted underneath.

Dennis.

[Eric Ho]

Thanks for the tip Dennis, yes this was a trial attempt to identify the fouling you talked about. There is indeed more clearance to mount it the way you described.

On another note - during the wheel build and bushing installation: it's important to make sure the bushes are deburred (one end of these bushings are a little 'closed' perhaps due to the parting or cuttoff in processing). So that the axles pass completely through. Also during the bush installation into the wheels, make sure they are completely seated (I find it good to have at least 5mm depth on the open end of the wheel type shown below. Otherwise they would bind against the fastener during tightening down and won't turn smoothly.

Bushing depth

Fully seated

I reamed (12mm) and sanded the seating surfaces on the wheel side before fitting in the bushes. Measure to make sure depth and seating was correct, tightened on axle to test and turn, before using loctite 638 to retain the bushes.

A final pass team/sand (slightly undersized below 10mm) through the bushes before installation on the axles helps eliminate any slight binding or friction arising from concentricity differences or burrs/edges. The aim is have these as free running as possible before adding the tracks.

[Ray Brown]

Nice Eric. Keep the posts coming. I like seeing progress.

Ray

[Eric Ho]

Just to show the 2 positions that the steering tie rods could be, over or under.

Over

Under

Wheels being tested fitted to check for binding, etc. Only the hubs for the outer type B wheels used now to check first.

Right side up

[Eric Ho]

In the midst of pinning the tracks, and trial assembly of the upper half. I came across this site with different photos of the different versions of the 251. http://www.sdkfz251.com/

Also putting on the motion pack

Pinion

Also was delayed by an endless search for the M3x6 grub screws (24 pcs), but only had a pack of M3x3 (also 24 pcs), used to lock the idler arms. Guess M3x3 is used instead?

On setting the suspension angle for the idler arms, I initially used an inclinometer app on my smartphone, after setting the chassis level. If measuring the angle is too troublesome, the vertical drop is about 3.75mm (20 deg) to 7.5mm (15 deg) from the bottom of the chassis to the centre of the wheel shaft.

[Dennis Jones]

Yes I used the M3 X 3 mm grubs and they are ok, I think the 6 mm would have been too long anyway.
As you may have read in one of my posts I pinned the arms on the lhs anyway.
After setting up the rearmost suspension arm I then used a depth gauge to do the rest.

Dennis.

[Eric Ho]

Dear Dennis, thanks again for the confirmation on the M3x3. I will use these and see how it holds up first.

On another note, my hands now have that 'charcoal' look after handling the tracks. Just to check on how others here 'treat' their tracks? Does anyone prime/paint them? I assume also that the split pins are cut shorter - otherwise there is quite a lot of the leftover pin to wind around, etc?

[Dennis Jones]

Yes you need to shorten the split pins to about 8 - 10 mm total length. I just use a car aerosol to spray the tracks usually graphite grey. I do a lot of outside running so the tracks will weather themselves in over a period of time anyway.

Dennis.

[Dennis Jones]

I have just looked at that website :- http://www.sdkfz251.com/ Eric and there is certainly a lot of info and photos on there, I would advise any other builders to look at it if they need inspiration for colour schemes etc.

Dennis.

[Eric Ho]

Thanks for the tips Dennis. Sorting out the tracks and pinning for the time being:

Painted links

Pins, bent and cut

And measuring those arm angles

Digital protractor

Meanwhile, some interior work, relatively simpler to detail if needed to,

Driving compartment

Detail photo from Sdkfz251.com