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Go Back   Madabout Kitcars Forum > Mad Build Area > Marlin Sportster, Cabrio, Berlinetta and Roadster builds

Marlin Sportster, Cabrio, Berlinetta and Roadster builds Enthused or Confused about your vintage Marlin build? Ask away here or show off your build.

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  #21  
Old 8th October 2015, 22:06
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yep, I'm going to check the fit of the shaft both at the diff end and the spigot on the gearbox. I do seem to remember having to open out the hole in the gearbox end so it would fit like Robin said, but that it was still a pretty snug fit. The front was custom made to my P.C.D specs where as I think the rear was an off the shelf part for a BMW. I also had to open up the bolt holes on the diff end of the shaft to 11mm as the P.C.D wasn't quite perfect but as the locating ring was ok, didn't think it would make any difference. Maybe I screwed it up.

I have the day off tomorrow so can get stuck in without having to fight the dark and the unsociable aspects of rev-ing a car at 8-9 in the evening.
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  #22  
Old 9th October 2015, 16:38
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I think I may have tracked down at least part of the problem. I carried on disconnecting the drive shafts today and the problem was still there so I bit the bullet, dropped the exhaust and then the prop. With the prop shaft out, the car runs perfectly smooth up past 60 in 5th with no issues which confirms that the flywheel, clutch and gearbox aren't part of the equation. Here's a pic of what I found when I inspected the prop.



The diff end flange on the prop has a raised section which mates with a recess on the diff input flange to ensure it is centralised. As you can see, there is yellow paint stuck tight on the flange now which is the torque paint from the diff input pinion nut. This means the flange must have been tight against the input shaft end and it's therefore likely that the prop wasn't seated properly even though the bolts were done up tight. It may even have been affecting the pre-load on the pinon nut though I suspect it would take a bit more than that.

I'm going to send the prop back to the manufacturer and get a recess cut in the end and also get him to recheck the balance, run out, misalignment and generally reconfirm the measurements from my drawings.

I now have the fun of putting all the other disconnected parts back on the car. Having the car up in the air while I'm waiting will give me chance to improve a few things I'd put off until after the IVA such as the gearbox and exhaust mounts.

Last edited by morris; 9th October 2015 at 19:46..
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  #23  
Old 10th October 2015, 09:17
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Looks like you are homing in on the problem. I'm not familiar with BMW parts but that location spigot step is much lower that I have seen on other cars. Worth putting a vernier across it and comparing with the mating recess? As there is so little to locate on it may not be very effective in centralising the flange. Peter.
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  #24  
Old 10th October 2015, 10:44
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Hi Pete,

It's exactly 2mm high but I've a drawing bailey-morris supplied for the same part way back when I was first getting quotes and that says 3mm max. You can see the diff input flange below. There is a very shallow recess to fit into and in this instance, I can see that I need to spend some time cleaning the surface up a bit too as there's a small amount of rust left in there. I really could do with getting the face of the diff flange machined too as you can see some corrosion top and bottom where it wasn't covered by the original BMW UJ.

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  #25  
Old 10th October 2015, 11:47
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Interesting. I wouldn't do any machining on the flange as you would have to reset all the diff preload as you would have to remove it to do the job. I would do some very thorough hand scraping to just remove all the rust scale and then a smear of waxoyl to inhibit further corrosion. If you have an old flat file and grind the teeth off and then put a slight radius on the end it will do a good job of the scraping.

Just a thought. Was your special flange fitted before the prop was balanced? It should have been. Did you remove the flange to enlarge the holes and if so did it go back on the yoke in exactly the same position or was it replaced 180 degrees from original? Peter.
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  #26  
Old 10th October 2015, 12:39
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Yeah, it's the pre-load issue that puts me off removing the input flange. I was thinking that some careful swipes with a fine file avoiding the un-corroded areas would be the best approach.

As far aware, the prop was balanced with both flanges fitted. When I opened the holes out 10mm to 11mm, I did it with everything still attached, I've never actually separated the slip joint as there's never been the need.

It's in the post so I just have to wait and see now.
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  #27  
Old 10th October 2015, 20:37
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Best avoid files as they cause raised areas at the edges of the cuts. An engineers scraper (made cheaply as above) is the preferred method and you will be surprised how well you can locally remove metal (or rust flakes) without disturbing the surrounding metal. Secure the flange in a vice and use both hands, one to do the pushing bit but the other to control where you are workig. Peter.
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  #28  
Old 11th October 2015, 11:36
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Good advice Pete. I actually found a broad gasket scraper amongst my tools and that did the job nicely.



I used a screw driver to scrape the corrosion out of the recess and then blocked the face of the flange with some wet and dry. I also ran a small wire brush wheel around the inside of the recess with a dremel to ensure there was no crud left in there to spoil the fit.

It's now lovely and smooth with very little corrosion left (as you can tell by the brightness of the flash reflection). I've smeared a little copper grease over it now just to keep it that way.
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  #29  
Old 11th October 2015, 17:05
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Good result eh! Will be interested to hear the results of the checks on the propshaft when you get it back. Peter.
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  #30  
Old 16th October 2015, 12:04
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Any news yet about the propshaft? Peter.
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  #31  
Old 16th October 2015, 18:22
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Best not to get me started. Having posted the prop back to Autoprop UK on Saturday morning, Parcel Force have been incapable of finding the address until 5pm today despite 4 calls in the evening over the week to explain how to get to a location that is clearly visible, with a sign from the main road. I can see it nearly 200 miles away using google street view so they must be pretty incompetent as I could find my way there with nothing more than an AA road atlas if not memorising the route.

I'm pretty sure the £17 it cost me was for a ParcelForce48 service, not ParcelForce152.

I'll let you know once Autoprop have come back to me. It should be a pretty simple job to take the yoke off, machine the back and re-assemble.
cheers
Ian
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  #32  
Old 16th October 2015, 23:17
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How completely frustrating for you. Why is it that the more automated and computerised things become, the people that use them seem to lose all sense of direction, location initiative and common sense! Ah well soap box put away now! Hope the wait for the prop is worth it in the end. Peter.
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  #33  
Old 22nd October 2015, 09:11
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Hi Ian. Any news back from Autoprop? Peter.
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  #34  
Old 22nd October 2015, 17:44
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Hi Pete,

I spoke to Mike down at Autoprop on Tuesday to make sure he understood the problem but he hasn't got back to me yet. I'm going to chase tomorrow as the days are getting colder, nights drawing in and I want to get some shake down time on the car before the winter. Hopefully he'll have good news for me.
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  #35  
Old 22nd October 2015, 21:48
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Hi Ian. Fingers crossed then. I will be really interested to hear what caused the vibration when it is finally resolved. Peter.
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  #36  
Old 28th October 2015, 16:35
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Hi Ian. Any news from Autoprop? Peter.
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  #37  
Old 28th October 2015, 20:13
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hi pete, my prop should be winging its way back to me at the moment. hopefully I'll have it by the weekend, get time to fit it and report back.
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  #38  
Old 28th October 2015, 22:06
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Quote:
Originally Posted by morris View Post
hi pete, my prop should be winging its way back to me at the moment. hopefully I'll have it by the weekend, get time to fit it and report back.
Hi Ian. That's good to hear. Did Autoprop offer any comments about the possible cause of the vibration or what they have done to fix it? Peter.
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  #39  
Old 29th October 2015, 18:07
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My prop is back



They've not done quite what I asked for which was to cut a recess a certain size concentric to the the locating part but this dish shape should still work just as well. It's the same principle used on the BMW part (pic courtesy of peterux)



I noticed that the balance weights originally welded on are now missing but there's fresh paint, so maybe it was incorrectly balanced from the start too? Or maybe it's now going to locate properly but be out of balance

No time to fit it tonight but should know if my problem's solved by Saturday

Last edited by morris; 29th October 2015 at 18:09..
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  #40  
Old 30th October 2015, 17:40
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Quote:
Originally Posted by morris View Post
I noticed that the balance weights originally welded on are now missing but there's fresh paint, so maybe it was incorrectly balanced from the start too? Or maybe it's now going to locate properly but be out of balance
Let's hope this one is good!
Looks to me like that is a completely different flange so hopefully they have rebalanced the whole shaft. The 'scooped out' cavity looks good but the raised locating spigot looks a bit shallow?
And I can't understand what could have caused those tangential scratches? As a custom propshaft builder I'm a bit surprised they don't have a standard BMW diff flange.

Hope you enjoy the next test drive
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