Marlin Roadster (Re)Build

[peterux]

Nice work, Robin.
Was there a reason for the bottom trunion being threaded? It seems an odd thing to do?
How do you keep the new thread lubricated, maybe some waterproof marine grease?

[MartinClan]

Originally Posted by peterux

Nice work, Robin.
Was there a reason for the bottom trunion being threaded? It seems an odd thing to do?
How do you keep the new thread lubricated, maybe some waterproof marine grease?

The upright rotates in the trunion using the thread. It effectively un-screws and screws-up a little every time you turn the steering wheel. It's ancient technology inherited from the Morris Minor. Quite why they didn't fit a balljoint instead I will never know. There is a massive balljoint at the top of the upright where it joins to the top arm. They could have put similar at the bottom.
The thread is lubricated using one of the 2 grease nipples on the trunion. The original design only had a single grease nipple which is why not much grease ever reached the thread. And made worse by lack of regular maintenance.
My guess is that the majority of Marinas still out there have worn threads on the upright. I think as long as you fill them full of grease before the MOT the tester doesn't notice.

Cheers, Robin

[peterux]

Thanks for the explanation, Robin.
I guess it was probably a cost thing?
I had an Austin Healey Sprite (aka Midget) that had threaded fulcrum pins that wore out the lower wishbones in the same way. We lived in a terraced house then and I can remember changing the wishbones in the gutter outside the house.

[Mick O'Malley]

My ex-REME tester threw up his arms in horror when he discovered I'd greased my trunnions. He insisted that Hypoy should be used, so I mended my ways, bowing to his superior knowledge.

Regards, Mick

[AlanHogg]

Morris Minor /Marina trunnions should be greased. Certain Triumphs eg TR6 and Reliant Scimitar which use TR trunnions should be gear oil. that said its always been a bone of contention within the Triumph group.

[MartinClan]

Doing a bit more on preparation.

First the front hubs. The good news was they still had the original Timken bearings - or so I thought.... However when I looked at one of them it was totaly trashed inside. It looks like a bearing had broken up at some time judging by the damage. Even the step which locates the bearing outer race was destroyed. Someone had done a quick fix and popped in a new bearing but that's not really an acceptable solution so I am looking for a replacement.
damaged hub by Robin Martin, on Flickr

And the brake calipers. They are almost the same as those used on the Triumph Spitfire (Girling type 14) so there are plenty of replacements available. But, after experience with buying bits for the engine I am a bit suspicious of some of the stuff that is available. So I thought I would have a go at stripping them - keeping in mind they are at least 50 years old and haven't seen any use for at least the last 30!
Following a good tip I cut the end off an old flexi brake pipe, screwed the uncut end into the caliper and used my compressor to blow down the other. This allowed me to have the caliper safely in a bucket at arms length just in case any of the pistons came flying out!
Three of the four came out "easily" but the last one wouldn't budge.
Now I followed another good tip! I put back the piston in the caliper with the stuck one but in an almost out position. I then filled the caliper with water (yes really) with the bleed nipple screwed up and then a spare bleed nipple where the brake line should go. I used a couple of clamps to push back the "good" piston and Hey Presto the water pressure was sufficient to get the stuck piston moving! Amazing!
Finally I split the calipers. You are not supposed to do this but I couldn't see any other way of properly inspecting and cleaning the bores. There is only a single O ring to worry about and this comes with the refurb kit you can get from Bigg Red. And, suprise suprise, everything looks good even though there was rusty crud in most of them!

stripped calipers by Robin Martin, on Flickr

[MartinClan]

I have made some new adjustable tie bars following what has been done in the past by other Marlin owners. They comprise the front part of the old tie bar, a turnbuckle and some rose joints. The idea is not so much to make the suspension adjustable but to be able to dial out any inaccuracies in the chassis geometry. From what I have read this is not uncommon. I am going to remake the U shaped chassis brackets as I don't think my first attempt looks substantial enough.

tie_bar1 by Robin Martin, on Flickr
tie_bar2 by Robin Martin, on Flickr

Cutting the 1/2" UNF thread on the tie bar proved tricky. Ideally a lathe should be used for larger external threads but I don't have one. I do however have a decent pillar drill - so I used this to drill a perpendicular 1/2" hole through some substantial box section. I then attached this to the die holder positioning it with a 1/2" UNF bolt. The hole through the box section acts as a guide resulting in a perfect thread on the item to be threaded.

modified_die_holder by Robin Martin, on Flickr
die_holder_use by Robin Martin, on Flickr

I should say the guide wasn't my idea. I found the basics on t'internet after a failed attempt at cutting a thread.

[Dpaz]

What a brilliant hack and so simple. Thank you! But did you forget to mention the cap screws, or did I not read it right?

[MartinClan]

Originally Posted by Dpaz

What a brilliant hack and so simple. Thank you! But did you forget to mention the cap screws, or did I not read it right?

Yes - over simplified description! Once positioned using the bolt, you attach the box section guide to the die holder using whatever mechanism suits. I just drilled through the die holder and box section and use a couple of M4 screws.

Cheers, Robin

[MartinClan]

Front suspension rebuild has moved on to fitting the hubs. At this stage I was feeling fairly smug with the bargain triumph wire wheel adapters I had bought from Ebay as a trial fit seemed to be good.
However when I came to fit them properly I found they didn't (fit). The hub casting, where the grease cap fitted, fouled the inside of the adapter. "Easily" fixed by some heavy duty filing. I then found that the wheel studs have a large shoulder on them, great for centering the wire wheel adapter, but unfortunately preventing the nuts securing the adapter to be screwed fully home. Hmmm. after some head scratching I made a thin, 1mm, spacer which did the trick. now everthing fits OK :-).
So the front suspension is pretty much complete and I would have a rolling chassis - if my wheels had any tyres on them,
Some pictures....
hub_before by Robin Martin, on Flickr

hub_and_spacer by Robin Martin, on Flickr

front_suspension1 by Robin Martin, on Flickr

[Patrick]

Looking good

[MartinClan]

I have been making slow progress once again. This getting old certainly slows things down a bit. Plus the more than occaisional holiday...

The chassis is finally all cleaned and primered. I am going to coach paint the bodywork so I thought I would practice on the chassis. This means a further coat of primer, 2 x undercoat and 2 x topcoat. Could take some time, especially as I am going to do it in two halves - first the front as far as the windscreen and then the rear. There is a convinient weld in the chassis at this point to which I can paint up to. I have also painted the front and rear bulkheads. I remade these from zintec some time ago and, although rust resistant, are not rust proof.

chassis_in_primer by Robin Martin, on Flickr

The plan was always to convert the car to cycle wings but I have seen a few Marlins where this has been done but where the rear wings were retained. So I have dug them out of the weeds and given them a clean. Before and after picture.

rear_wings_clean by Robin Martin, on Flickr

One of them though has a real bodge with part of it being ground away. I assume this was to aid fitting - who knows. Anyway, I don't like bodges so I have started to repair this.

rear_wing_bodge by Robin Martin, on Flickr

While the fibreglass is out, and my hands itching, I am also modifying the radiator surround, no pictures yet though...

[Dpaz]

It's comming on well , looking really good,

[MartinClan]

After a considerable ammount of fettling I finally have an acceptable radiator surround.
It was orginally fitted very badly and I struggled to get a better fit until I finally discovered the whole moulding is on the sqiff! Once I had worked that out I managed to get a reasonable fit although still not 100% square at least it looks OK to the eye. In the process I filled many holes and extended the sides down so they touch the chassis rails. Needed as I will be using cycle wings so this part will be visible. I also did a bit of re-inforcing arround the edges and filled in the gap that is normally visible between the front horizontal edge and the bumper. (Later cars have a neater wrap arround bit that fitted arround the bumper and provides somewhere to mount the number plate.)

rad_surround by Robin Martin, on Flickr

[MartinClan]

I have repaired and trial fitted the rear wing that had been previously been bodged. Also filled the many holes previously used to fix it as I wanted to start again. And.... filled the ragged holes where the lights were fixed. I am planning on using some round Lucas style lights rather than the original Marlin supplied Rubolite ones
As I am fitting cycle wings at the front I have also shortened the rear wing removing the stub of the running board where it would have joined to the front wings. Considering the original plan was to fit cycle wings all round it actually looks pretty good. The fit of the wing is not the best though - nothing I have done - that's just how it was made. But by the time I fit some wing piping the gap that appears at the top will disappear (I hope). I could probaly pull the tub and wing together a bit more but I didn't want to over stress 40 year old fibreglass.
On to the other wing now....
rear_wing_repair by Robin Martin, on Flickr
rear_wing_fitted1 by Robin Martin, on Flickr
rear_wing_fitted2 by Robin Martin, on Flickr

[Patrick]

Looking good

[MartinClan]

I have almost finished painting the chassis using CraftMaster coach paint. This requires a minimum of 6 coats, 2 x primer, 2 x undercoat and 2 x topcoat hence the long delay since I last posted (Plus I have had Covid). Although it takes ages to do the result is worth it.
I have done the main chassis in black raddle which is a sort of semi gloss. It's tough as old boots once it has had a few weeks to dry.
The bit of the chassis that supports the windscreen frame, and the frame itself is MG Maroon and boy is it shiny. This will match the body colour. The final coat I applied using brushes made by Purdy which cost an arm and a leg but the result is worth it.
chassis_painted1 by Robin Martin, on Flickr
chassis_painted2 by Robin Martin, on Flickr
Now all I have to do is paint the rest of the body!
Now the chassis is painted I have permanently fixed the front and rear bulkheads using a combination of stainless screws and mastic.

I have also made a new front grill using some stainless mesh, as the old "crinkly wires" used by Marlin are no longer available. It's a bit of a b*gger to cut but the result is quite pleasing.
new_grill by Robin Martin, on Flickr

[Patrick]

Nice colour

[MartinClan]

My first attempt at coachpainting some of the fibreglass. it's not bad even if I do say so myself. This was coat number 5 - the first topcoat. 6th coat (2nd topcoat) looked better but forgot to take a picture. Still a long way from perfect but good enough. The red, by the way, is considerably darker in real life.
coach_painted1 by Robin Martin, on Flickr

And now I have started to re-assemble the car in ernest. Near side front suspension is done. The big problem with the Marina is you cannot adjust the castor. Which in turn affects the steering self centering - big time. But at least with my adjustable tie bars you can tweak it. By measuring the angle of the torsion bar relative to the chassis I have established that the castor is bang on the suggested 2.5 degrees. Hooray. Note the Heath Robinson angle device!
castor_angle by Robin Martin, on Flickr

[peterux]

That's looking nice and shiny