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91
CNC / Re: It's new to me
« Last post by ddmckee54 on May 08, 2026, 10:52:17 PM »
I reprinted the shim for the X axis leadnut block.  I had calculated that I needed about a 4.1mm thick shim.  So I printed a 4mm shim - reasoning that it's a LOT easier to add to the thickness of a solid block than it is to subtract from it.  When I put things back together, sure enough the leadscrew WOULDN'T slip into the coupler.  This time it was hitting on the top of the coupler.  It was close enough that I could force it into the coupler, but then the leadscrew was jammed and it wouldn't turn.  I started looking around for something I could use as a shim.  Since I some old business cards laying around from an earlier attempt at leveling the base, I decided to give one of them a shot.  Dumb-luck strikes again, it was like baby bear's porridge - just right.  The leadscrew slips right into the coupler.  And, when turning the leadscrew by hand, I can't feel any difference in drag between when the leadscrew is in the coupler and when it's not.

I'm ninety-nine and forty-four one hundredths percent sure that brings me to a project milestone - the point where I'm done with the mechanical modifications and start aligning the bed to each of the axis.
92
CNC / Re: It's new to me
« Last post by ddmckee54 on May 07, 2026, 12:31:50 AM »
Progress has been made, tonight I put the Z carriage back in place. It feels stiffer, before when I pushed on the top of the carriage I could feel it flex - that's not happening now. I even added 15mm to the height of the carriage to compensate for the travel loss caused by the coupler. Here's what it looks like with the new Z carriage and the stiffening plates.

Adding that 15mm in height means that the leadscrew isn't long enough to reach reach the lower bearing anymore. I've got a replacement on order. but it's not due for a couple weeks yet. If by some miracle I get this thing running before then, the lower end can just run wild.

I also took a hard look at the alignment of the X axis leadscrew, both horizontal and vertical. Side to side it looks pretty good, it is DEFINITELY vertically challenged though. From what I can see, it looks like the leadscrew is about 2-3mm too low. With the leadnut block firmly bolted to the bed, I was able to get decent measurements from the top of the bed to the top of the leadscrew, from the top of the bed to the top of the coupler, the leadscrew diameter, and the coupler diameter. After running the numbers, I determined that my 6.17mm thick shim SHOULD have been 4.06mm thick. I'll have to add a stack of washers under the heads of the mounting bolts if they bottom out in the slot before they are able to clamp down. I don't think I've got the extra 2mm of clearance under the clamp that would be required by the thinner shim.
93
Vendor Specials and Announcements / eBay auction: Last remaining 1:3.5 scale Gypsy Major engine castings kit
« Last post by Boo on May 05, 2026, 04:56:59 PM »
I have decided to sell my remaining Reinhold Krieger designed 1:3.5 scale De Havilland Gypsy Major engine castings. This is eBay item 256719913071, link https://www.ebay.co.uk/itm/257491053600  Initial bid is set to GBP849 with no reserve, end date is Thursday 14th May at 19:05 BST.

I do not have drawings available for this kit unfortunately as I sold them with the previous castings but I will try to make second generation drawings available.  I hope, but do not guarantee, they are adequate.  Sorry but there it is.

Auction blurb follows, for pix see the eBay item:


Quote
You are looking at a set of Castings for a 1:3.5 scale De Havilland Gypsy Major I engine in new & unmachined, completely unmolested condition.

NOTE: Pix of the actual castings for sale are up now but there may be more to follow as I will try to put up pix of the 2nd generation drawings (see below) later to help people decide how much use they will be.

NOTE ALSO: that although a couple of pictures are provided of a completed engine for the information of the viewer this auction is solely for the castings set as described below.

The kit comprises the following:

Cast parts: (37 parts)
Crankcase
Housing cover
Gearbox housing
Gearbox housing cover
4 x Cylinder Head
4 x Rocker Arm Cover
4 x Rocker Arm Bearing
Intake Manifold
4 Carburetor Parts
Oil Filter
Oil Chamber with Cover
2 x Ignition Distributor with Cover
Ignition Adjustment Lever
2 parts Oil Pump (Bronze),
2 parts Petrol Pump (Bronze)
4 x Pistons

Moulded parts:
2 parts cooling air duct (black plastic)

I do not have an original set of drawings for this set and the buyer will need to source these separately.  However I may be able to provide 2nd generation drawings but cannot guarantee they will suffice to build the model.  I think they will do but I am not guaranteeing that and the onus is on the buyer to find a set of drawings.  Sorry, but there it is.

The prospective bidder should be aware that only what is pictured will be provided, this is the castings kit I have available.  Once again, the picture of the completed engine is for the information of the bidder only, it is not included as part of the purchase.

A competed example of these engines fetched upwards of ?9k at auction at Christies some time ago so the builder will have a rare item of real value that is close to unique - only a very few of these kits were ever made and fewer built up.  I bought two full sets of castings and sold the other one and the drawings last year.  It's pretty unlikely another set will be auctioned on eBay any time soon, so...

Observant viewers will have seen that this engine is to a larger scale than is common at 1:3.5.  This means that it is quite a big engine.  The specs that follow are from the original supplier and are for information only are not guaranteed to be correct :


Scale-rebuilding of the original engine of the Tiger Moth
Inverted 4 cylinder inline engine OHV
Scale: 1 : 3,5
Weight: about 7 Kg,  measurements: l= 35 cm, w=18 cm, h=25 cm
Displacement: 140 cc
Stroke: 41 mm
Bore: 33 mm
Compression: 1:8,5
Fuel: Methanol with 3% synthetic oil
Oil: 15 W 40
Turning direction of the prop ( seen from front side) is clockwise like the original
Prop: 26? x 16?
Turning speed: min: 900 r/min, max: 4000 r/min
Firing order: 1-3-4-2
Timing:
Inlet    from 20? before TDC until 60? after LDC
Outlet   from 65? before LDC until 15? after  TDC

I am willing to sell this to the UK,  W. European countries, the USA and Australia + NZ using eBay's Global Shipping program, sorry if you live elsewhere but that's it.
94
CNC / Re: It's new to me
« Last post by ddmckee54 on May 03, 2026, 12:22:44 AM »
I got the spindle slide and the Z carriage reprinted, I even designed and printed the X axis leadnut block, That should be the last of the mechanical parts that need to be printed - I think!

I took the bed back apart, installed the leadnut block shim, and put it back together. There's a little binding as the leadnut approaches the motor end, it's not as noticeable at the other end. I just centered the leadnut block between the bearings, and I suspect that it's not quite lined up correctly side to side. The T8 leadscrew WILL flex, that's why I don't notice the drag when the bed is in the center of its' travel. When the bed reaches the end of it's travel to the motor end, the non-adjustable end of the leadnut is only a few mm away from the motor coupling. When the bed reaches the end of its' travel in the other direction, there's still about 80-100mm of leadscrew between the leadscrew support bearing and the non-adjustable end of the leadnut. That 80-100mm of leadscrew would explain why I notice the drag at the motor end, and not so much at the other end.

My current plan is to remove the bed and loosen the leadnut block enough that it can move, but not easily. I'll then put the bed back together and run it back and forth a few times, that should let the leadnut block find its' own center. Then, it'll just be a matter of carefully removing the bed, tightening the leadnut block mounting bolts, reassembling the bed, and trying it again. If it still binds after that, at least I'll know that I've got a vertical misalignment problem and not a side to side problem.
95
Member Videos / OKMO R01 Rider Ericsson Stirling Engine Modified
« Last post by Jim Dobson on May 02, 2026, 07:56:00 PM »
I made a new timber plinth for the engine as well as a larger copper water cooling reservoir, reshaped and straightened the copper piping, cut some brass and made some brass bolts on my lathe and scraped the red paint from the outside of the brass flywheel.
The R01 is a beautiful miniature model of the Rider Ericsson Hot Air Engine and a pleasure to run.

96
Member Videos / Re: My week this week, my workshop videos!
« Last post by hermetic on May 02, 2026, 12:03:29 PM »
Hi Folks,
We are completely knackered! another week of field work, to catch up on what we didn't do last year because we were both ill! Health has returned, and with it just enough strength to reverse the  nature takeover bid, and reach new heights of organised chaos!
Phil, in almost too hotto garden East Yorkshire

97
CNC / Re: It's new to me
« Last post by ddmckee54 on April 30, 2026, 09:47:54 PM »
I was assuming that the motor shafts had been hardened, but I tried a file on one and it cut.  The hacksaw made fairly quick work of whacking 10mm off the end - so I guess I was wrong about the hardness.  I found that the Z carriage will flex.  If I can make it move by pushing on it - it'll move under load.

I'm in the process of redesigning both the slide and the carriage.  I'm going to bolt 1/8"x1-1/2" HRS on both sides of the carriage to keep it from flexing.  Since my carriage mounting plate is 84-ish mm wide, the spindle slide is 90mm wide, the carriage is 60mm wide, and I've only got 24mm from the carriage mounting plate to the back of the spindle slide when I need 40mm...  I need to play around with the numbers, get creative, and see how things look in the 3D model.
98
The Water Cooler / Re: Help from MEM Mods takeII
« Last post by ozzie46 on April 30, 2026, 07:04:24 AM »
Hurray!!!! I'm back on!
Thankyou, thankyou, thankyou!!  You're the best Adve.

Ron
99
CNC / Re: It's new to me
« Last post by ddmckee54 on April 30, 2026, 12:27:18 AM »
Mechanically, this is starting to come together.  I got the Z leadscrew cut to length, I installed the Z leadscrew, I disassembled the bed enough to remove the X leadnut block, I installed the X leadnut assembly in the leadnut block, and I reassembled the machine enough to measure the gap between the bed and the top of the leadnut block.  When I designed the leadnut block I wanted to be sure that my block wasn't too high, so I subtracted 3mm from what I had sketched out and printed the block.  I must have already subtracted that 3mm when I drew the sketch, because when I measured the gap it was 6.17mm.  It's no big deal, I'll just print a 6+ mm shim instead of a 3+ mm shim.  Here's a view of the gap from the motor end of the leadscrew.


This is a view from the other end of the leadscrew.


One thing I discovered when assembling the Z leadscrew is that the 84 oz-in stepper motor shafts are about 10-15mm longer than the original motor shafts were.  That gap you see between the blue coupler and the Z axis motor shouldn't be there.  I'm going to lose about 10-15mm of travel on all three axis when I install the larger motors.
100
The Water Cooler / Re: Help from MEM Mods takeII
« Last post by AdeV on April 29, 2026, 07:44:51 PM »
Hi Ron,

I've adjusted the ban that was catching you to be more filtered... it was set to total overkill & I think might have been catching far too many people... please try again & let me know how you get on!

Cheers,
Ade.
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