REPORTS ON A 1914 HUMBERETTE RESTORATION

[alsfarms]

Hello Mike,  Kevin has a nice car.  Have you considered have a pair of new rods build?

Al

[chistech]

6 hours ago, Mike Macartney said:

 

MIke, yes. The measurement from the top of the combustion chamber to the top of the piston on one of the two cylinders is nearly 4mm different. That is why I started my investigations to find the reason why. And then I started to find more problems! It now looks as if the trimming work will be finished before the engine is back together and running. Never mind, at least it keeps the brain cells working.

Maybe you could get some of those kids turning Joe’s lathe to push you around until the mechanics are sorted. I’m sure you’d have as much luck as Joe would  having that happen!

[Mike Macartney]

12 hours ago, chistech said:

I remember reading in your thread (at least I think I read) that you thought one piston was incorrect to the engine.

 

Chris, Thank you for your thoughts. All ideas and thoughts are always worth consideration.

 

I have started to get in a bit of a muddle as to who's messages I have replied to and who's I've not! Sorry to anyone I have missed out, thanks for all your posts.

 

 

 

 

[Mike Macartney]

2 minutes ago, chistech said:

Maybe you could get some of those kids turning Joe’s lathe to push you around until the mechanics are sorted. I’m sure you’d have as much luck as Joe would  having that happen!

 

I could then call it a Humberette Go-Cart and enter the Red Bull Soap Box Derby! Another alternative is to temporally fit a Briggs and Stratton lawnmower engine!  

[chistech]

20 minutes ago, Mike Macartney said:

 

I could then call it a Humberette Go-Cart and enter the Red Bull Soap Box Derby! Another alternative is to temporally fit a Briggs and Stratton lawnmower engine!  

Hey mike, just a little useless trivia you might not be aware of. That B&S engine has “old car” roots written all over it and would be semi-appropriate. B&S used to make all the locks and keys for the early GM cars. Possibly other Marques I’m unaware of too. Here’s a picture of their logo. The BASCO meant Briggs and Stratton Company. 

[Mike Macartney]

Here are some more photos of taking apart the bottom end of the V-twin engine.

 

 

These bolts holding the locking plates for the nuts on the locking plate were not very tight.

 

 

The locking plate was tight and needed some gentle persuasion to come away from the nut.

 

 

It slid off eventually.

 

 

I bagged up the parts and labelled them

 

 

On other vintage motorcycle engines I have worked on, these big end journal nuts have always been extremely tight. Holding the flywheels is always a problem when trying to undo them

 

 

I decided to try using the impact wrench first. The nut wasn't that tight, it spun off with ease.

 

 

Cracking the taper is often a problem. I 'bounced' one flywheel on the wooden block and it all fell apart. All a lot easier than I thought. Hooray!

 

 

This is a split pin stopping the main secondary conrod from turning. It will be interesting to see if it should have been a taper pin? There is a lot of slack in this conrod bearing.

 

 

It looks as if there is another pin on this side.to stop it going in too far or maybe to stop it rotating.

 

 

The big end shaft knocked out with a slight knock with the copper/hide mallet. I thought I was going to have to press it out. I am sure that is not a 'factory finish' to those rivets!

 

[mike6024]

The offset pin, for the shorter connecting rod, alters the timing, meaning how many degrees of crankshaft rotation is needed to get from the first piston reaching top dead center, until the second piston gets to TDC. So the spark firing timing would need to change if a single crankpin arrangement were used.

 

Here's 3 videos of Humber flat twin engines running I found interesting.

 

https://www.youtube.com/watch?v=hZHxlDzlAmo

 

https://www.youtube.com/watch?v=ni_qh7cphQc

 

https://www.youtube.com/watch?v=st6oebC8Wgc

 

 

[Mike Macartney]

10 minutes ago, chistech said:

just a little useless trivia you might not be aware of. That B&S engine has “old car” roots written all over it and would be semi-appropriate. B&S used to make all the locks and keys for the early GM cars. Possibly other Marques I’m unaware of too. Here’s a picture of their logo. The BASCO meant Briggs and Stratton Company.

 

I did not realise, I have just found this on the internet:

 

http://www4.briggsandstratton.com/miscpdfs/RNT/history of briggs_MS8751.pdf

 

It seems they also took over the Smiths Motor Wheel company in 1991. They were used mainly on bicycles to motorise them.

 

 

Thanks Chris, for the information.

 

 

[mike6024]

Here is mentioned the hinged second connecting rod, for 1911 Humber V-twin motorcycle.

 

1911 Humber produced a striking new 2.75 V-twin model of 339cc. The engine was unusual in having a master connecting-rod to which the second rod hinged. The Bosch magneto was gear driven and clamped to the rear of the crankcase, the carburettor B and B, and Druid forks used. It performed particularly well on its debut at the TT - with all six entries finishing and a win.

 

http://www.gracesguide.co.uk/Humber:_Motorcycles

 

[Mike Macartney]

Which way round should the conrod go round?

 

 

This is the way it was round when I took the engine apart. It looks wrong to me!

 

 

My feelings are that it should fit in this way, so that the secondary conrod is pushing against the main conrod on the power stroke. Your thoughts would be appreciated.

 

It would then be as shown in the original parts drawing, shown below.

 

 

This maybe be the reason for the difference in compression height?!?

[JV Puleo]

Go with the drawing.

All of the old machine parts books I've looked at - and I assembled my B&S milling machine with that as my only source of information - show the parts in the orientation they were assembled. I suppose they may not have given that much thought but we should remember that there were no "shop manuals" in 1914. The exploded parts drawing was all anyone had to go by and Humber was making a very different sort of motor so I think they were probably very careful how they illustrated it.

 

It's easy to overthink these situations. I do it constantly. Perhaps the best approach is to trust the original design and reassemble it after renewing all the bearing surfaces. I might even add a bronze bush to the secondary rod with an oil groove going all the way through.

 

Actually, I'd make a larger pin for the secondary rod, bush the hole and lap the parts to match each other. You could unquestionably get a better fit that way and even if the car has little mileage on it, I suspect all those parts are worn.

 

jp

Edited June 20, 2019 by JV Puleo (see edit history)

[Mike Macartney]

Thanks Joe, I'll go with the drawing and reassemble it, just to see if it has made the compression height equal on both cylinders. I have found more problems on the bottom end; loose rivets holding the cast iron flywheels onto the steel main shafts! I am jig making at present to enable me to drill out one rivet accurately on the milling machine to see what I am up against. As you say - it takes more time to make a jig than do the actual job!

 

I have had a email from a Kevin in Australia who tells me this:

 

A fellow in South Australia fitted Harley Davison rods to his Humberette and I understand it went – in Aussie language – like a shower of shit  i.e. well.  With the Harley fork and blade, you get both rods onto the crank as they ought to be!!

 

I will try and see if I can make contact with the guy to find out more.

[Mike Macartney]

I think I have found the reason for the difference with my dial gauge measurements on the flywheels when I mounted the crankshaft and flywheels between centres on the lathe.

 

 

Loose rivets holding the cast iron flywheel onto the main shaft of the crankshaft. I actually found it by accident. I had cleaned this face off with a cloth and lifted it up by the shaft to turn it over to wipe the other side and noticed the oil seeping out of the side of one of the rivets. After finding this one loose rivet I notices that most of them had movement in them.

 

 

I have highlighted the rivets in white so that you can see the oil seepage better.

 

 

The rear flywheel also had loose rivets.

 

 

This is a view from the other side of the flywheel. Presumably the hammer and chisel marks are where somebody has tried to 'tighten up' the rivets.

 

 

Can you see the split pin that stops the 'big end pin' of the secondary conrod rotating in the housing.

 

 

Before attempting to drill out a rivet I set one half of the flywheel and shaft in the lathe to clean the worse of the 'stick-out' bits off. The idea being that it would be easier to find the centre of the rivets. The gap between the revolving centre and the rivets was too small to get a decent size cutting tool in.

 

 

I took off only 0.005" at a time.

 

 

 

 

[JV Puleo]

That's the way to do it. If you take off most of the upset end of the rivet they may just knock out. I'm skeptical of rivets though not knowing how much material there is I'm not sure what the alternatives might be. I'd look at fine thread, low head socket cap screws with nuts torqued down to the prescribed amount for the thread and with Locktite on them.

You are making real progress there.

 

It's nice to know there is a HD rod that fits though I've no idea if that expression means it went like crazy or if it flew into pieces.

Edited June 20, 2019 by JV Puleo (see edit history)

[mike6024]

It sounds as if the "poop hitting the fan" might mean a raging success in Aussie-land, which is not what it means here in the U S of A.

 

[mike6024]

Flopping the connecting rod assembly over should not change the compression heights; not of either the short or the long one.

 

The maximum "height" for the short rod occurs when the wrist pin, the crankshaft axis, and the pin labeled #12 in the parts diagram all fall on a straight line.

 

 

[Spinneyhill]

1 hour ago, mike6024 said:

It sounds as if the "poop hitting the fan" might mean a raging success in Aussie-land, which is not what it means here in the U S of A.

In this country it means "trouble".

 

12 hours ago, Mike Macartney said:

like a shower of shit

To me, that would mean it went poorly.

 

Oh well, viva la difference!

[Mike Macartney]

 

I have just looked the expression up in the 'Australian Slang Dictionary'

Go Like a Shower of Shit

phrase

Go very fast.

Example of 'Go Like a Shower of Shit'

I tuned up me Torana and now she goes like a shower of shit.

 

It's a new one on me, the expression in the UK would be 'It went like shit off a shovel' which I believe comes from when we had steam trains.

 

Anyway enough of this crap talk let's get back to my bottom end!

[Mike Macartney]

 

I found a better lathe tool to remove the worst of the high points of the rivets.

 

 

Now I needed to find the PCD (pitch circle diameter) of the rivet holes.

 

 

I guessed they would have used a 'normal' size for the radius. My guess was 3/4".

 

 

I set the lathe tool to the centre and then moved it out on the lathe cross slide by 0.750" and moved the tool in to scribe a centre line for the rivets.

 

 

Now to try and find the centre of the rivets and scribe a line at 90 degrees.

[Mike Macartney]

12 hours ago, JV Puleo said:

I'd look at fine thread, low head socket cap screws with nuts torqued down to the prescribed amount for the thread and with Locktite on them.

 

Joe, thanks for the tip. I was thinking, if the rivets are countersunk on the thrust side of the flywheel, using countersunk socket cap screws to fix the flywheels back onto their shafts. When I get the rivets out successfully, I will be able to see how much 'meat' I have to play with.

 

12 hours ago, JV Puleo said:

I've no idea if that expression means it went like crazy or if it flew into pieces.

 

4 hours ago, Spinneyhill said:

In this country it means "trouble".

 

I was going to say that maybe it means the opposite of what we in the Northern hemisphere say because the Australians are from the Southern hemisphere! (upside down) but so are you ! ? !   So that can't be right!

[Mike Macartney]

6 hours ago, mike6024 said:

Flopping the connecting rod assembly over should not change the compression heights; not of either the short or the long one.

 

Mike, I see what you mean. It is still a 50 degree angle between the cylinders.

 

 

I had better check my measurements and calculations for the combustion height, the distance between the top of the piston at TDC and the top of the cylinder head, I could have gone wrong somewhere.

[Spinneyhill]

1 hour ago, Mike Macartney said:

Southern hemisphere! (upside down)

LoL! That is just the hegemony of the Northern Hemisphere talking. On what basis are you not upside down?

Edited June 21, 2019 by Spinneyhill (see edit history)

[Mike Macartney]

2 hours ago, Spinneyhill said:

That is just the hegemony of the Northern Hemisphere talking. On what basis are you not upside down?

 

Well, that's a big word! I had to look up the meaning as I hadn't heard it before. It's no wonder I failed my English exam three times!

 

Up here in the North we have our feet firmly planted on the ground!

[Mike Macartney]

Drilling out the loose rivets in the crankshaft assembly. This will be the first time I have tried to used this milling machine for drilling.

 

 

The first thing to do was to make something up to clamp the flywheel and shaft onto the mill table. As I have no big blocks of solid metal I used sections of box to raise the main shaft away from the table. Now to find a bar to clamp it down.

 

 

I found a length of 30mm box section into which I cut to size and drilled holes at each end for the clamping bolts.

 

 

After drilling with a centre drill I used a 4mm drill, as at this stage I don't know the diameter of the rivets.

 

 

I then very gently drilled with an 8mm drill.

 

 

. . . . and out popped the countersunk part of the rivet.

 

 

A sharp blow with a small drift knocked the rivet out - success!

 

 

While I remembered, I marked the flywheel and the shaft flange with centre punch marks.

 

 

After also marking where my centre punch marks were with a marker pen I measured the diameter of the original rivet hole with my set of metric drills, that go up in size by 0.1mm. The result was that the hole was between 7 and 7.1mm. I am assuming the rivets would have been 1/4" and the riveting was done while the rivets were red hot. The drilled diameter being larger than 1/4" to allow the red hot rivet to pass through the hole. Don't quote me on that because it is only my guess. It appears that the riveted holes are countersunk on both the shaft side and the flywheel side, which is going to make life interesting, if I am going to bolt the two parts together again!

 

I am pleased that the rivet didn't spin while drilling this one out. Only another 15 rivets to remove, but that can wait till tomorrow.

[JV Puleo]

Nice job Mike. I couldn't have done it better.

Also look at shoulder bolts - they have a ground diameter and the thread diameter at the end is one size smaller than the nominal diameter of the bolt. The heads can be turned down a little if too thick. I'd be inclined to install them a little proud and turn the entire thrust face, bolt heads included, at the same time. They are generally between .0005 and .001 smaller than a reamed hole which might be fine or you could try to get an undersized reamer for the holes so the fit would be tight. You'll need clearance for the nuts so figuring this out requires a decision on what you are going to use for connecting rods. At this point, I'm inclined to favor the HD rods if you can get some information on whether it worked and what rod was used. I don't know if shoulder bolts are available in the UK in English sizes but if not, I can get them and send them on.

 

If you used a 5/16 shoulder bolt the thread size would be 1/4-20

Edited June 21, 2019 by JV Puleo (see edit history)

[JV Puleo]

In looking, I see they are available in metric sizes. I'd pick the closest size very slightly larger than the hole and use that, reaming both pieces together, inserting a bolt, and then reaming the next etc... If you have the first bolt in place, the holes will align perfectly. I'd keep inserting bolts so that when the last hole was reamed all the others would be in place. You should mark exactly where the flywheel was in relation to the center so it can go back in precisely the same place. You cannot assume that the original holes were perfectly uniform. When that is done and the pieces are bolted together, you can take a very fine cut on the faces of the flywheels and the diameter to true it up.

 

If the relief for the rivet isn't deep enough the hole can be counterbored just enough to sink most of the head of the bolt.

Edited June 22, 2019 by JV Puleo
typo (see edit history)

[Mike Macartney]

Thanks Joe, your a real Pal. Yesterday afternoon I had a look at the different types of bolts that were available and came across the 'shoulder bolts' you mention and saved the page in my favourites. Today I hope to remove the rest of the rivets. It is proving quite exhausting for me using the mill to drill, as the travel on the part of the mill that moves down, (I can't think of the proper name), is not enough when I change from the centre drill to a larger size drill to drill the top of the rivet out. I have to move the table down change the drill and then move the table back up, but I'll get there in the end. I'll see how I get on this morning.

[Bush Mechanic]

Hey, Mike, you are going great. I do enjoy your posts.

 

I think the bolt idea is sound, if you can find clearance, and enough meat left in the job, but they would need to be virtually a press fit in the holes if you are going down that road. Properly riveted, they would swell right through to create a very tight job. And as Joe said, do them one at a time before you remove the originals. Remove one, replace, then move on to the next. It will then retain the original balance.

 

Hot riveting pulls the two halves together nicely, but when it cools the shaft fit goes away. That looks like a cold rivet job, to me, starting off with a very snug rivet fit. 

 

And to set the record straight, yes, going like a shower of sh..  does mean it's going like a cut snake. And if the poo hits the fan, it's definitely all gone pear shaped. Pretty logical, I reckon.

[JV Puleo]

The part that moves down is the quill. I have the same problem with my mill, especially as I have no quill so I have to drill by raising the table. I have power feed, which I usually use but there is no "feel" for the drill or cutter - all the parts are much too heavy for that so if something is wrong you won't know until it breaks. I also don't have very much travel which is another reason why I bought a true vertical mill. Now I just have to put it back together.

[Mike Macartney]

Thanks Bush Mechanic for your kind words and your ideas. It's great having people to talk to about these sorts of problems. Living out here in the 'sticks' in North Norfolk there are a few friends that are interested in 'old cars' and engineering, but not many that I know that take on 'silly projects' like this one!  I didn't read your post until this afternoon and by that time I had removed the rivets and separated the two parts. Photos etc to follow.

 

3 hours ago, JV Puleo said:

The part that moves down is the quill. . . .

. . . . I also don't have very much travel which is another reason why I bought a true vertical mill. Now I just have to put it back together.

 

It was quite early this morning, when I wrote the post, for the life of me, I couldn't think of the correct name. I didn't think at the time to look up 'milling machine parts' which I should have done.

 

In the end I just used a 4mm drill and then a 8mm drill to remove the rivets and then I didn't have to keep winding the table up and down. I am sure you will get your true vertical mill back together eventually.

[Mike Macartney]

Removing more rivets on the flywheel assembly.

 

 

The rivets all drilled out nicely using a 4mm drill and then a 8mm drill. I could then use the quill feed to drill them out rather than having to keep moving the table up and down. The rivet holes are 7mm.

 

 

This is the inside part of the flywheel and has the recess for the flange on the main shaft for the transmission end of the crankshaft.

 

 

I decided to note down the dimensions of the parts so I can then draw the assembly before deciding on the best option for fixing it to the flywheel.

 

 

The face of the flange. The thickness is just over 5mm less the countersink. I had hoped that there maybe enough metal to thread these holes - it looks a bit thin to me for that?

 

 

This is a close up of the flange face that sits in the recess in the cast iron flywheel. I wonder if the rust on the surface didn't help the trueness of the flywheel face? The car was stored in a damp barn for nearly 70 years.

 

 

This is the part on the flywheel where the flange sits.

 

 

This face has the steel washer that runs against the bronze bush in the rear crankcase.

 

 

Do you think I can get away with a polish on this main shaft?

 

 

The face of the bronze bush in the rear casing, after only a little cleaning up with fine wet and dry.

 

A question - can specialist companies now weld cast iron to steel?

[alsfarms]

Nice pictures Mike.  Looking things over, that you have posted, I am thinking that you may want to go with a solid good grade and snug fit rivet as has been mentioned before.  Put the squeeze to it cold so it firmly fits/expands into the ID of the the hole and will not shrink after cooling as the potential is with a hot rivet.  I am concerned that using a bolt will not stop the potential movement unless you do a press fit bolt.  Maybe lightly apply heat to exp[and the holes and freeze your chosen bolts so you would end up with a very tight, shrink fit to lock the flywheel in place.  Here we go again....just my 2 cents....

Al

[JV Puleo]

I suspect the rivets were set cold with some sort of hydraulic rivet set. They were common in boiler making and I doubt anyone would have done it with a hammer. The need to get uniform pressure on all of them would make that nearly impossible. That said, I am skeptical of using them now because we don't know exactly what they did or how they did it or have the needed tools. Bolts, if they can be fit, just need to be torqued down to whatever the prescribed pressure is. After all, flywheels were bolted on all the time, either with a flange or with a taper and a big nut. As far as fit is concerned, the most important dimension is the fit between the flange and the counterbore in the flywheel. If that is tight, the OD of the rivet (give or take .0005) is relatively unimportant. The rivets were loose because they stretched, something that will not be a problem with a bolt tightened properly. Just to be certain, I'd choose a shoulder bolt that was slightly larger than the hole and ream the holes to match. If necessary, I'd get a reamer .001 or .0005 undersize - these are usually readily available because a light press fit with dowel pins is often needed. I'm not sure I've got the arrangement of the shafts and flywheels straight in my mind but that counterbore for the head of the rivet looks perfect for the head of a shoulder bolt although it may have to be turned down a bit.

 

Another thought would be to thread the steel thrust washer to accept the bolt end... again, I don't know what the thicknesses are but if it is a thick washer that might work. You'd need a rotary table to make it but I remember you saying you had one.

 

I don't think you can weld steel to cast iron. Brazing, or silver solder would likely be the preferred method but I'm very skeptical of using extreme heat on any of these parts.

 

You have to mike that shaft and see if it's worn. It may be that, even if there is some play all you'd have to do is replace the bushing.

[mike6024]

I don't think shoulder bolts are needed here. Flywheels are commonly bolted to crankshafts without shoulder bolts. There is a recess cut into the flywheel that fits over the end of the crankshaft, and that centers the flywheel. And the bolts hold them together, they supply an axial force (compression force along the axis of the crankshaft) but do not help to locate it, just hold it on. I am thinking of the flywheel on my car, but others are like that.

 

I have a shoulder bolt on my starter, it acts like a locating pin, so it precisely locates the starter pinion gear, relative to the flywheel ring gear.

 

In the case of this Humberette, you need the shaft and the flywheel to be concentric and perpendicular. The axis of the shaft and the center axis of the flywheel need to coincide (concentric). The shaft fits through the hole on the flywheel, so this should guarantee it, the concentricity. And if you bolt the flange to the flywheel, the flange fits into the recess in the flywheel, so the face of the flywheel should be perpendicular to the axis of the shaft.

 

So I think you need bolts to hold this tight together, but not shoulder bolts, as other features guarantee the alignment.

 

[mike6024]

There'd be nothing wrong with shoulder bolts though. Just saying I don't believe they are really needed for locating purposes. In this case the holes in the flange would be sized to fit the shoulder snugly, and the thread would be cut into the holes in the flywheel.

[Mike Macartney]

Thanks guys for all the information and thoughts. I need to check the clearance I have to 'play with' on the outside and inside of the flywheel faces before I decide what to do. I have found a company in the UK that seems to stock various shoulder bolts.

 

https://www.accu.co.uk/en/564-ultra-low-head-socket-shoulder-screws

 

 

 

[JV Puleo]

9 hours ago, mike6024 said:

There'd be nothing wrong with shoulder bolts though. Just saying I don't believe they are really needed for locating purposes. In this case the holes in the flange would be sized to fit the shoulder snugly, and the thread would be cut into the holes in the flywheel.

 

I'm certain that is correct. I only suggested shoulder bolts because of the low head and the nut being a smaller size, not knowing what clearances Mike has to deal with. Also, even if the diametrical clearance isn't critical there is nothing to be lost by overdoing the precision.

[Spinneyhill]

If you want precision and certainty, you need shoulder bolts or similar that fit the holes. If you use friction bolts (i.e. smaller than the hole and rely on tight nuts) there is always the possibility a loss of friction will allow movement. We are not allowed to bolt chassis together for this very reason, or at least to replace a rivetted part such as a cross member with another bolted in.

[JV Puleo]

RR chassis are all bolted together - or at least the ones I'm familiar with are. I've mostly only worked on pre-war cars. The technique was to drill the holes undersize then line the parts up perfectly. I assume fixtures of some sort were used but they didn't rely on the drilled holes which would almost certainly be a tiny bit oversize or not in perfect alingment. After everything was lined up, the holes were reamed with a tapered reamer, known today as a car reamer or a bridge reamer. Then they were bolted together using the reamed holes. Years ago I read that they used tapered bolts so when I had a rusty RR chassis in the shop I purposely took some bolts out...they aren't tapered and I'm guessing that the writer knew about the tapered reamer and just assumed the bolts must be tapered as well.

[Mike Macartney]

I agree that shouldered bolts, used on 'more modern' flywheels, would be fine - BUT - "'Houston we have a problem!"

 

 

There is not a lot of room here for a bolt head.

 

 

There maybe some room if I could find some conrods were "fork-and-blade" style. I wonder what length conrods they used in the Rolls Royce Merlin engine?!?

 

I wonder if the hammer marks are somebodies idea of tightening the bearing?

 

 

The thickness of this flange at the end of the main shaft is only 5mm thick, less the 90 degree 'chamfer' for the rivet. In this photo I am checking the runout on the shaft where it goes through the cast iron flywheel. It is virtually zero. Next job is to check if there is any runout on the flange face that sits in the recess in the flywheel. Any discrepancy here will be magnified by the time it is gets to the outer edge of the flywheel.

 

 

On the inside of flywheel recess there are these marks. Presumably due to the slight movement between the surfaces with loose rivets? I'll have a look at the shaft flange to see if it is the same on that.

 

 

This was a photo I took of the flange after I had cleaned it, at the time I hadn't thought of looking for any marks. I will inspect it more closely latter.

 

 

The bight marks in the chamfered holes must be where I just kissed the cast iron flywheel with the 8mm drill I used for drilling out the rivets. The heads of ultra low head socket shoulder screws are only 2mm thick so possibly these could be used if there is room to get nuts or a plate with threaded holes on the other side.

 

This job certainly gets the old brain box working!

 

Thanks again for your thoughts and comments, they are appreciated.