Building a Redwing

[Jasonb]

There should be no  about it. Oilite bearings are supposed to compress when pressed into their holes, they are over bore and over diameter as supplied but if the hole is correctly sized when fitted the bearing's bore will come down to a suitable fit .So you may find the bore is oversize at the moment in which case your crank issue could be even worse.

Unless you are never going to take the caps off after boring then oilite is not ideal as you may end up with an oval bearing bore as the caps close down and dontt give such an even compression all round. Maybe stick to the bronze specified in the drawings unless you adjust holes and shaft diameters to use the oilite bush in an uncompressed form particularly as the casting may not be rigid enough for a proper spec press fit

Might also want to check that the previous owner did not make the crankshaft to "fit" the oilite bearings in their supplied state and your push fit has closed them up a bit.

Is it tight for the full rotation or at specific angles, if so that is usually the sign of a bent crank

[Twizseven]

Jason,
I appreciate that Oilite bushes would normally be a press fit and shrink slightly.  When out of the mains the bushes are a nice fit both on the two crankshafts I have and also on the 1/2" (.499") diameter silver steel rod I also tried. I intended to use them in the uncompressed form.  The bushes are a very firm thumb into the housing if the bearing caps are done up tightly (as when bored).

I was given two fabricated crankshafts with the engine and neither of the cranks turn smoothly.  They alternate between being stiff and then slightly less stiff.  In both cases the main shafts are slightly loose in the webs and can be seen to move as can the cross-drilled pins, supposedly locking the webs to the main shafts.  Chucking one end in a collet chuck and running the lathe slowly the free end prescribes a circle.

I think I will have to start afresh and go for another fabricated crankshaft.  I've not done one before.  The plans show material as 4140 steel.  Is there any reason why I could not use the Silver Steel bar I already have?.  If I can use the Silver steel what would be best material for the webs.

Colin

[crueby]

Movement of the shaft in the web? Thats not a good sign!

[Alyn Foundry]

Hi Colin.

You’re progressing nicely.   

Have you checked the crankshaft’s in the lathe yet? I presume you have the luxury of a Collet chuck? If yes, first “ clock “ a known sample of Silver Steel then replace it with the crankshaft. Any deviation can be addressed usually by slight pressure through a Dead centre from the tailstock. Otherwise you can resort to the “ judicial tap “ delivered by a hard Rubber mallet.

We always centre spot the main shaft at either end before Silver soldering the webs this helps with sorting any distortion that may occur during the heating process.

   Graham.

Edit.

I should have read your post fully lol…. Purely my opinion but pinned webs are useless in an IC Engine. Without the additional support of hard soldered joints the pins will become loose in no time. In fact they already have….


<a href="https://www.youtube.com/watch?v=QwlmaAIzUMU" target="_blank">http://www.youtube.com/watch?v=QwlmaAIzUMU</a>

[Jasonb]

Bit of black MS flat bar for the webs and you could use the silver steel if you have it, I tend to use precision ground Mild Steel. Silver solder as Graham says and you don't really need to pin itif you can see the solder has flowed through the webs.

You are lucky if your bearings fit wobble free as supplied, usually if being used uncompressed the shaft needs to be turned to fit and usually ends up a few thou over nominal.

Some cankshafts made by others need a bit more than a gentle tap to get them running true

[Twizseven]

Graham,
Thank you for posting that video.  What sort of clearance do you have between the web and the shaft to allow the solder to wick through.  I guess that with a hit and miss engine the crankshaft does take more stick and pinned joints are not really suitable.

How easy is it to clean the flux and solder from the bearing surfaces?  I assume Citric Acid or similar will remove the flux deposits.  Is it a case of polishing with emery to remove solder residue or putting in lathe and turning it off.

Jason,
I have the silver steel in stock and should have some Black MS.  I remember that picture, you put it up a year or so ago.

Looks as though it will be new silver soldered crank.  I have silver solder, flux and Sievert torch with 3525P cyclone head.  Up to now my silver soldering has not been very good.  The last job I tried I ended up getting the Oxy/Acetylene torch out and brazed the job up.

Colin

[Jasonb]

If you have a 1/2" reamer that should be OK for the holes in the webs.

Feed the solder in from the sides where the main shaft will be cut and the outer ends of the pin to keep excess to a minimum. Tippex (solvent based) can be used to stop solder getting where you don't want it.

Use Tenacity No5 or CuP's HT5 flux as it stays active longer

[Twizseven]

Jason,
Thanks.  I should have the 1/2" and 7/16" reamers.  I have got some Cup Alloys EF flux and about 4 off of their 1.0mm 455 silver solder rods (55% silver).  Is that enough solder?  Would the EF stay active long enough or should I just get a pack of the HT5.
Colin

[Jasonb]

Should only need a couple of inches of rod at the most, HT5 would be well worth getting I use it for almost everything these days.

[Alyn Foundry]

Hi Colin.

I see Jason has answered your questions. There’s no need for any “ exotic “ metal in the crankshaft’s for this type of model, they’re definitely not racing engines.

I have different reamers for different jobs. For the webs I use one that has always cut  a couple of thou over 1/2” diameter.
Thoroughly clean each component and set the assembly on a flat level firebrick. I only use Tenacity Number 5 flux, mixed to a thin cream consistency. As you’re assembling the parts ensure that all joints are covered with the paste. I also use a counter sink on the inside of the webs to create an extra solder width.

As for quantity, believe it or not I find that a 1/8” diameter ( 3 mm ) rod cut to 3/16” ( 4 mm ) lengths is adequate for each side of the joints @ a 1/2” diameter. I place the cut pieces pressed firmly into a blob of flux at the top of each joint.

To reduce the risk of warping you start heating the shaft from either end, the metal will start to lengthen to its maximum and then you can put the heat into the centre where the joints are. You will first see the flux change and become watery looking this is the time when you might have to tease the solder chunks to stop them dropping off. Keep the heating constant then the solder “ drops “ and the joints are made. Look all around and if you don’t see a Silver ring on the other end you can go in with the fluxed rod and just add a little extra. Once happy, remove the heat and let the crankshaft sit overnight. Always an evening job here….

I use undiluted White spirit Vinegar for pickling. Again best done overnight or at least a good 12 hours.

You can then use a fine Emery cloth to polish up the discolouration, a little light oil helps. I use the lathe to radius the pin web and I have recently made a jig to radius the shaft side. Wish I’d made one years ago. The jig goes into my 4 jaw chuck.

The last part of the job is to cut out the section between the webs, you’ll know if things haven’t gone well if it springs open.
All that’s left is to gently mill the cut ends flat with the webs. If you had a spring “ moment “ the centre spots will aid you in bringing it back in line….

I’ve made hundreds of crankshaft’s this way over the years and am pleased to report, not a single broken one. Had the odd warp though.   

   Graham.

Photo 1. Crankshaft jig.
Photo 2. In a pickle.

[Twizseven]

Graham & Jason,

Thanks for all that info.  This will take a few days to get sorted as will need to order the flux.

Think I will continue with conrod and its bearing assuming I have the steel flat.  Will machine from solid rather than silver solder the bearing flange and wrist pin end.

Colin

[Twizseven]

I was given two fabricated crankshafts with the engine and having looked at them both I think I will have to start afresh. In both cases the main shafts are slightly loose in the webs and can be seen to move as can the cross-drilled pins, supposedly locking the webs to the main shafts. Chucking one end in a collet chuck and running the lathe slowly the free end prescribes a circle.

Whilst waiting for silver solder and HT5 flux for the new crankshaft I decided to make the conrod. With some kits the conrod is a brass casting and in some cases if no casting it can be made from a single piece of steel or fabricated from three parts silver soldered together. I decided to follow the single piece of steel option.

Started with a 5.125” x 1” x 0.5” piece of BMS. This was set up in the vice in a vertical position and edge finder used to locate centres in both X and Y axis’s. The top was squared off taking light cuts due to the large amount of stickout above the vice. The end was centred and whilst setup a 2.5mm hole was drilled down through the centre for distance of 0.75”. This is the feed hole for the oiler. Two holes were also drilled 3.5mm on 0.75” centres and these were tapped 8-32. These are for the two bolts holding the brass main bearing to the conrod.



The piece of steel was then turned end to end and set up vertical again. Again the top was squared off taking light cuts due to the large amount of stickout above the vice. This end was then centred. The conrod blank was then moved over to Myford 7 lathe. The 4 jaw chuck was fitted and centres put in tailstock and headstock spindle. The conrod blank was held between centres and the jaws closed on the ends and sides. Jaws 1 and 2 then released ½ turn and blank removed (this will make setting up after the next step a bit easier).

Conrod blank moved back to mill and setup with 1” side resting on pair of parallels and the drilled and tapped end aligned with left hand end of vice. The DRO is set so that absolute zero for X axis is left hand end of vice and for Y axis is rear face of vice. The hole for the gudgeon pin (wrist pin) was drilled 7.7mm and then reamed 5/16” at a position on the centre line 4.638” from left hand end.

A quick tidy up of the corners and then turned through 90 degrees to rest on a parallel. 5/8” dia endmill then used to trim the material by 0.250”. The drilled and tapped end finish dimension is 0.20” so took end mill to 0.21” leaving rest to be turned off in the lathe.



When one side completed steel is turned over and the second side machined similarly.
Conrod blank now looks a little more like a conrod.



It is now put back in the lathe. The big end fitting back between the previously set jaws. A wooden spider was made to hold it off the back of the chuck (centre in the spindle is no use now). Jaws tightened and DTI used to check conrod is centred.



Then spent several happy hours setting the topslide to give 3/8” per foot taper and then swapping lathe tools around to turn the taper. This was a right pain in the ass.



Finished off by turning the material away from the tailstock end to leave a ½” cube with the little end in its centre. The tapered shaft was then cleaned up with a file and polished.

Conrod then back to mill to put a 3/8” flat 0.7” from left hand end ready to drill 4.1mm and tap 10-32 UNF for the oiler, this was followed by a 0.062” oiler hole for the wrist pin. This was then countersunk slightly using a centre drill.



Last task was to round off the little end. Did not want to remove the vice or angle plate with the jig plate on it. There was not enough space for the 6” rotary table. I then remembered a Vertex 4” RT I had bought 10 plus years ago and never taken out of the box. This just fitted on a pair of parallels and clamped down diagonally across the table. Luckily the chuck mount off the 6” RT fitted on the 4” RT. Chuck mount centred under spindle and DRO zeroised. Found ¾” dia offcut from scrap bin, chucked it up in 3 jaw then drilled and tapped it M8. Chuck then moved to RT still with spigot in jaws. An M8 allen bolt with a short plain section used to hold conrod on the spigot. Then carefully radiused the end taking quite light cuts.



Rightly or wrongly I kept left hand lightly on unsupported end of conrod in case the bolt did not hold. Bolt held but the chuck wanted to unscrew and had to be tapped firmly back into place.





Quite pleased with end result. Now onto the big end bearing itself.

[RReid]

You have good reason to be pleased with that result. Nice job!

[vtsteam]

Beautiful! 

[Kim]

Very fine looking conrod!
Kim