Doris NP Super Dexta rebuild

This forum is about the Fordson Dexta, Super Dexta and Petrol Dexta.
tom lad
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Re: Doris NP Super Dexta rebuild

Post by tom lad »

Dextrous wrote:Its only lightly worn but I think I would rather have a solid pin that is not an interference fit so I can take it out at will. :wink:

fair piont m8 but i'd reuse the old one tbh , if the ends aren't to loose , its lasted the last 50 years .

the only bush i could find was half width so i had to use 2 , a link pin lives thu the role to make sure the dont come out , they should of been a few thou. bigger . think they are cat 1 - cat 2 bushes ?
Some mornings I wake up grumpy, but most mornings I let her sleep in.

Tubal Cain
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Re: Doris NP Super Dexta rebuild

Post by Tubal Cain »

Paul,

From what you have said the liners are not too badly worn and unless you intend to work the tractor hard I would use your existing liners with new piston rings. You need to remove the ridge from the top of the liner to avoid the possibility of the top ring breaking.

Gerald

Dextrous
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Re: Doris NP Super Dexta rebuild

Post by Dextrous »

So, in a an effort to get my engine to the agricultutal engineer (Jim Fielden of Lineholme garage Todmorden) for new liners fitting and honing, I've took the timing case cover and took plenty of photos of the timing marks on the gears, the engine is on its side with the crank to the left in the following photos. I'm reading the manual and following figure 8 the engine replacement guide.

when I first took off the timing cover the timing marks were alligned like so
Image

After turning the crank a few times the marks on the oil pump, camshaft and fuel system gears and marks on the idler gear in the centre line up
Image

I shall now continue to dismantle

Cheers
Andy

Dextrous
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Re: Doris NP Super Dexta rebuild

Post by Dextrous »

Well its time for my annual update, can't rush these things :D

Kids, work, getting hitched and other projects including work on the house and a toylander for the kids have got in the way. Also I needed to rebuild a couple of milling machines, one of which is needed to bore out the front axle ovality and put a bigger bush in it. I'm also going to fit a home made pin as I find the after market ones have poor tolerances and I think the original design is poor, I'm going to fit a greasing mechanism.

So just got to adjust the gib strips on the milling machine, bolt the axle securely then bore her out.

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I only got the power to the mill wired up yesterday, it seems to run fine, I bought it from a technical college in Essex, advertised as imperial and 3 phase, turned out to be single phase and metric :lol: . I have renovated most of it, not the head though, I shall see if it needs an TLC before cleaning it up and spraying it, so boring out the axle should be a good test. There's a big chip out of one of the pulleys which I need to fix but that just effects available ratios and possibly balance.

The pin is normally hollow to accept a starting handle which isn't much use on a diesel so I will make a solid pin with a small hole drilled along part of its length with a grease nipple on the front. I will then drill through this at 90 degrees where the bush sits and mill a couple of grease grooves. I shall use EN24T for the pin or similar. Something like this.

Image

Regards
Andy

Bensdexta
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Re: Doris NP Super Dexta rebuild

Post by Bensdexta »

Dexterous, how very good to hear from you :beer:

My tractor has been busy now for over a year, and I've been oiling the axle pin on a fairly regular basis - well OK when I remember. :wink:

My pin seemed to fit pretty well in the bushing, so no prob with tolerance so far. And all together with your excellent spacers! My local machining man, who is brilliant, has suggested that rather than making a whole new pin, we just fit a smaller dia pin with a tight tolerance, inside the existing hollow pin. Then tack weld it in place. Then drill the ways for the grease and fit nipple on the front. Won't take much of a tack to keep it in position, indeed the cut-out for the front locking plate would almost do it. That way we keep the hardness of the hollow pin.

The new pin needs to be quite long as you've shown, so it's accessible for greasing at the front of the nose cone. That's my plan!
Bensdexta - 1961 working for a living!

Dextrous
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Re: Doris NP Super Dexta rebuild

Post by Dextrous »

Hi Ben

Good to here she's on the road :clap:

Interesting, the new pin I bought about 5 years ago is very loose in the supplied bush however its a good fit in the oversized oilite bush (with supposedly the same ID) I'm using after boring the axle out to get rid of the ovality. So I could do similar.

Only issue is that if the new pin is made from EN24T which is hard but easy to machine, its crap for welding so OK as a one piece pin but maybe not as a composite pin as you suggest.

I shall have a play, I've also bought a decent MIG recently and have been practising so I shall see if the pin will take a weld.

Cheers
Andy

Dextrous
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Re: Doris NP Super Dexta rebuild

Post by Dextrous »

I had a measure last night and although the pin fits the new oilite bush better, its still a bit sloppy so I've bought some 45mm EN24T steel and will machine a new pin complete with greasing facility, an oiling point would be better but grease more practical. The bush is 1-3/4" so 44.45mm ID. I have asked the steel stock supplier if its true 45mm or 1-3/4" as sometimes they are assumed to be one and the same, its 45mm +/- 0.1mm so should be good enough.

I have the plan for holding down the axle on the mill sorted, it will sit on a 3mm aluminium plate, I shall wind down the boring bar until it touches the plate then set the mill's depths gauge half a turn more. I'm boring it out to around 0.1mm undersize and my mate is going to take the axle and bearing to work and use liquid nitrogen to fit it. Once that's complete we will machine the pin, I may ask my mate do that at work as his work's lathes are better than mine and his experience far exceeds mine. He will also bore the central hole and the cross hole, I shall mill the grease grooves.

Bensdexta
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Re: Doris NP Super Dexta rebuild

Post by Bensdexta »

Sounds like a plan. :wink:

How deep will you make the grease groves?
Bensdexta - 1961 working for a living!

Dextrous
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Re: Doris NP Super Dexta rebuild

Post by Dextrous »

Just a couple of mm Ben, with a round nose end mill. I renovated an old rapidor mechanical saw a while ago and did something similar for the pulley shaft, slightly different use but similar age :)

Bensdexta
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Re: Doris NP Super Dexta rebuild

Post by Bensdexta »

Dextrous wrote:Just a couple of mm Ben, with a round nose end mill. I renovated an old rapidor mechanical saw a while ago and did something similar for the pulley shaft, slightly different use but similar age :)
Where do you put the grease grooves relative to the 90deg grease ways?
Bensdexta - 1961 working for a living!

Dextrous
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Re: Doris NP Super Dexta rebuild

Post by Dextrous »

hi Ben

Longitudinally just under the bush. I could get fancy and put in a slight spiral as I have the necessary tools but setting it up would take ages and I may end up making a cock of it :D If the pin is push fit having the groove shouldn't make much of difference even if it lines up with the direction of force on the pin.

Cheers
Andy

Dextrous
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Re: Doris NP Super Dexta rebuild

Post by Dextrous »

Yes, I'm still focused on the Dexta :D I just received 4 litres of epoxy primer and 2l of hardener and a litre of thinners.Once I get the axle machined I will concentrate on getting the main casting cleaned up, moved down to the barn below the workshop and primed in epoxy. Although its 2 pack, there's no isocyanate content and can be sprayed in a well ventilated area (the barn) with a vapour and particle filter. The beauty of it is that unlike 1K primer its not hygroscopic so I can prep the various bits in stages then I shall spray it blue or grey next year before assembly when the weather improves without it rusting. It also sticks much better than 1K primer and is tougher.

I'm still prepping the axle before boring it out, here's it is nearly ready. I've got some family trips coming up that may slow me down a bit so it may be a couple of weeks before I get to do it.

Image

Cheers
Andy

Dextrous
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Re: Doris NP Super Dexta rebuild

Post by Dextrous »

This is the machine I have been boring the axle out with, its a early 60s Tom Senior, about the same age as the Dexta. I've renovated most of the machine except the head which I will do after this job once I know what needs sorting. The new bush can be seen on the bed.

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However it didn't entirely go to plan, here's the first few cuts, the first shows the wear caused by the pin waggling about on the casting with no bush.

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To use the new bush I needed to get rid of the wear while maintaining a 2" hole ID. Unfortunately this is 2" and there is still wear.

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So I was toying with the idea of using various bearing locking materials that can hide up to 30 thou but I thought sod it, I've got this far and while its set up I shall bore it out. It finally disappeared at 51.6mm ID so I took it out to 52mm.

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I then had to buy another bush, same ID but with an OD of 2 - 1/4" then turn it down to 52mm, which I am in the process of doing now.

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Hopefully the saga will be completed soon, I'm going to turn it down to say 52.1mm or so, put the bush in the freezer, warm up the axle slightly and get the press ready. I shall also put a very slight chamfer on one edge to guide it in.

Cheers
Andy

scoobyjim
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Re: Doris NP Super Dexta rebuild

Post by scoobyjim »

I love machine tools :clap:

Dextrous
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Re: Doris NP Super Dexta rebuild

Post by Dextrous »

Cheers Jim

Well after discussing getting the bush into the housing, working out the amount of contraction and expansion with cooling the bush and heating the axle with guys on the mig welding forum, I've decided to glue it in.

At first I was dubious about using loctite as I thought it would not stick to oilite, however there is a version, 603, specifically designed for oilite type bushes.

So I will be turning the bush down to a very snug slide fit, slapping some loctite 603 on it and gently placing it in.

This avoids getting the bush stuck half way, and as the metal temperatures equalise it would get stuck more firmly. I only have a fly press, not a 20 tonne hydraulic press.

I shall then move on to turning down a new pin.

Cheers
Andy

Dextrous
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Re: Doris NP Super Dexta rebuild

Post by Dextrous »

I turned the new pin down, much better fit than the replacement pin I bought.

Grease nipple fitted and pin drilled to get grease under the bush, I just need to mill a groove for the keeper and maybe for grease, I shall test it with the bush and grease gun first to see if it is necessary.

I'm sending a load of bits to be sandblasted tomorrow including the axle and axle carrier, once that come back I shall assemble and paint that section and move on to the engine.

Dry run with bush but no axle to ascertain where the slot for the keeper needs to be

Image

pin ready for milling the slots for the keeper

Image

Cheers
Andy

Bensdexta
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Re: Doris NP Super Dexta rebuild

Post by Bensdexta »

Excellent work :wink:
I'm all eyes for your next post!
Bensdexta - 1961 working for a living!

Dextrous
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Re: Doris NP Super Dexta rebuild

Post by Dextrous »

Thanks Ben

i've cut the keeper slot and the grease grooves, job just about done.

Here's the pin being milled, the keeper is on the bed. I cut through for the first 12mm then cut shoulders on each side as the keeper doesn't go near the middle of the pin.

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The keeper fits nice and snug. I made the keeper slot so it keep the grease slots at either side of the pin when fitted, not at the top where the main force is.

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Here's milling the grease slots, I stopped the slots short of the end of the bush by a couple of mm so the slots won't pick up muck and push it into the bush.

Image

next up are the rear wheels, pics to come as I will need some advice

Regards
Andy

Dextrous
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Re: Doris NP Super Dexta rebuild

Post by Dextrous »

I wanted to send a pile of rusty bits to the blasters, the rear wheel being part of it. I knew the tyres had decent tread and were a bit cracked but have been in storage in the barn for a few years, time to get them out and look in more detail.

The rims are both 9 x 28 as expected. although one of them needs to be renewed.
Image

The wheels have different tyres on them, similar sizes but different manufacturers, on is a Dunlop road/field master and the other a Danubiana. I'm not that conversant with tyre size nomenclature so here's my attempt at interpretation.

The danubia is 12.4/11-28R
So 12.4 is the width/section, 11 is the height of the sidewall and 28 is the rim diameter, all in inches. The dash between the 11 and 28 is supposed to mean crossply so what does the R signify?

The Dunlop says 12.4 - 28 which is a 12.4 section crossply with 28" rim diameter. So slightly different nomenclature. Obviously tyre sizing standards are such a good idea they had to have several of them :lol:

All this is a bit academic because as I need one new rim but the centres seem OK, the Agriline offer or similar from elsewhere of wheel and rim without centres seem good and I may buy a pair. The existing tyres are fine for a yard scraper, cracked but plenty of tread so I will sell them. I was going to get all posh and buy some Goodyears but they cost a gold pig and I'm not going in for shows and I'm not sure if a 6 ply or 8 ply tyre will make much difference to my usage.

I took the tyre off the good rim before I discovered the other was too far gone so I may put that back on and sell them on the rims with no centres. The held air before I played with them so I shall put new valves in and pump them back up.

Here's the tread

Image

And the cracks, dunlop first. They aren't too bad but seeing as I'm going to all the effort to do here up I though I would give her new boots.

Image
Image

Cheers
Andy

Dextrous
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Re: Doris NP Super Dexta rebuild

Post by Dextrous »

Just got myself a pair of new 12.4 x 28 Firestones, I'm picking them up on the 8th Nov. Just need 2 new rims, rim bolts and get the old centres shot blasted and the lot painted and the rear wheels are good to go. I sorted the front wheels and tyres a while ago.

I also picked up a pair of original but repaired wings so I can sell the repros I bought years ago, they fit perfectly as I trial fitted them before dismantling the tractor but they don't have the same profile as the originals. Perfect if you just want to keep the mud off and the old ones are beyond repair however the repaired ones weren't too expensive so I thought it woudl be good to keep it original. The repaired ones will need a bit of grinding and fettling but overall not bad nick.

if the weather stays warm I may try and get all the super dexta grey bits painted at the same time. This means I need to work how to straighten the seat.Its difficult to see it without the seat bolted down however its had some trauma in the past. Not sure which bit is correct so I will just aim to get it symmetrical and not leaning on the mounting bracket.

From memory, grey bits are :- wings, front and rear wheels, headlamps, butler wing lights, tool box, seat. Any more while I'm at it? :D

Here's the wonky seat.

Image

Image

Cheers
Andy

Dextrous
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Re: Doris NP Super Dexta rebuild

Post by Dextrous »

Well I made a right dogs dinner of the next bit of work.

I had a day free to play in the workshop and thought I would start renovating bits of tractor and stick them on the shelf ready for putting it all back together. The first component I refurbished was the steering box about 8 years ago so it was about time I did another :D

Its the usual refurb on the hydraulic top box, the lift pin

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You can see the worn pin and the rough cam surface clearly in this photo. After trying to push the pin out in situ using several methods including strong expletives it refused to shift so I was resigned to the fact that it had to come out. The top box is like one of those wooden puzzles, I managed to get the rear spring plunger out OK but to get to the pin most of the innards had to come out. Here's the lump on the bench

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To get the innards out you need to take the shaft that the quadrant sits on away. This is where it started to go wrong. I removed the quadrant handle with a puller, bad move, theirs a woodruff key in there and no way to get it out as the puller had pushed the shaft into the tube. I tried unsuccessfully to fish it out with various pliers but it was having none of it so I had to use brute force. Here's the quadrant hanging off with the woodruff key stuck :evil:

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and here's the damage afterwards, I think I can repair it but still annoying, the lesson here is to pull the handle off without pushing the shaft into the tube, not easy but doable.

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However I eventually got the bits out

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Here's the new pin and old, the new pin is the shaft of an old 5/8" drill

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Press the old one out and push the new pin in whilst resisting the urge to renovate the old fly press, I just have to concentrate on the tractor for a year. :D

Image

New pin installed, I just have to repair the damage I did in the process and smooth that cam a bit.

Image

Regards
Andy

Jerry Coles
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Re: Doris NP Super Dexta rebuild

Post by Jerry Coles »

Hi Dextrous
Couldn't help noticing that your using Metric spanners! The Dexta uses Imperial nuts and threads so I would suggest you invest (posh word for go out and buy) in a set of A/F spanners (open jaw and ring/combination) and sockets otherwise you will be rounding off nuts.
Jerry
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West Highland White Terriers, Dexta's, E27N's and DUKW's

Dextrous
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Re: Doris NP Super Dexta rebuild

Post by Dextrous »

The metric spanners were for the nuts on the puller that are metric :D

I do own a decent set or three of AF spanners, Britool before and after they split into a french company and a thinly veiled brand to cover far eastern imports.

Dextrous
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Re: Doris NP Super Dexta rebuild

Post by Dextrous »

I'm slowly getting there. I started stripping the block months ago, then a mate came around and finished it off so I took it to Lockstitch in Rochdale and had new liners pushed in and honed. The crank was fine, they supplied new bearings so I'm ready for the rebuild, first I gave the block a bit of a paint

I'm not going to paint everything empire blue like they did when the came out of Dagenham, I'll leave the wiring, rubbers and new bits as they are. Although I'm painting all the tin work with 2 coats of epoxy primer before synthetic top coat, I'm not doing that to the block or other castings, it tends to fill all the casting imperfections in and I think a tractor looks wrong if you hide this. So acid etch prime where the casting is back to metal. especially on the aluminium castings, then two coats of synthetic empire blue. Here's the block before I masked it up to keep out dust while attacking it with the knotted cup brush. Later it went into a hot tank at the machine shop which removed most of the crud. Before painting it had a good degrease with Upol slow degreaser.

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And here's after two topcoats. This was brushed on, the workshop was quite cool so it flowed on nicely and dried virtually brush mark free, however as it gets warmer I will add a touch of Owatrol oil.

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I'm cleaning the head up ready for painting now, its had new valves ground in etc. While I had the cup brush out I started cleaning the main chassis. It comes up well with a bit of effort but makes a right mess of the workshop so its going into the downstairs barn to finish it off. I brought it up in the first place because the downstairs barn wasn't finished, it now has a concrete floor, yorkshire boarding and lighting so much more ideal, one end is completely enclosed so plenty of ventilation but no chance of getting rain blown in so perfect for stripping and painting.

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I'm still not able to concentrate on the renovation as I have an extension to build on the house for the youngest daughter and I'm fitting a biomass boiler plus I've been asked to weld up a sculpture armature for an east London arts trail. The kids and work take up the rest of my time however my aim is to get all the components cleaned, fixed and painted this year and the engine rebuilt so I can assemble it next year.

Bluebilly
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Re: Doris NP Super Dexta rebuild

Post by Bluebilly »

I went to a local car boot sale and picked up a load of old A/F and Whitworth spanners (really cheaply) that I use to get at awkward bolts. I don't mind bending/grinding/shaping them to fit - better that than ruining my good sets.
1948 E27N
1958 Dexta
1969 DB 880
TEF 20
MF135 multipower
MF 165
MF 240

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