graeme Posted December 12, 2015 Report Share Posted December 12, 2015 The trunnion bolts on my TR250 need replacing. Is there any problem with replacing them with grade 8 bolts of correct length? Or, are they special bolts for some reason? Cheers Graeme Quote Link to post Share on other sites
RogerH Posted December 12, 2015 Report Share Posted December 12, 2015 Hi Graeme, I would imagine that a grade 8 bolt would be fine. The correct bolt is working in shear for the majority and is cushioned by the damper and the tyre. However without the spec of the correct bolt it is impossible to make accurate assessments Roger Quote Link to post Share on other sites
jerrytr5 Posted December 12, 2015 Report Share Posted December 12, 2015 Not special, just UNF grade 8.8, but I see that grade S is similar according to Namrick. http://www.namrick.co.uk/acatalog/tech-info.html Jerry Quote Link to post Share on other sites
RogerH Posted December 13, 2015 Report Share Posted December 13, 2015 Hi Jerry, it is interesting to see from the table that they measure their bolt lengths for the whole bolt - under the head to end of thread. This is quite a shabby way of doing things (although it is what is done in the automotive world) as you do not know what the shank length is until you open the box. In Aerospace the bolt length is from under the head to the end of the shank - the thread length being a ratio of the diameter to accept the correct nut. This way all the working layers are in contact with the shank and not the screw thread Also it is easier to specify a bolt length as you would normally know the thickness of the job. Moss and ALL the others do the same as Namrick Roger Quote Link to post Share on other sites
BlueTR3A-5EKT Posted December 13, 2015 Report Share Posted December 13, 2015 As Roger says - Original bolts were a shorter thread with a shank of suitable length to support the spacer bearing tubes. If the bolt you buy is based on price you will end up with something from a stock 'that'll do' range where the bolt is the correct length but the thread is longer and shank shorter than the orig. There is an UK maker of the correct bolt but his product is more than double the price of the 'that'll do' brigade. Pay Peanuts Get Monkeys. Peter W Quote Link to post Share on other sites
Chris59 Posted December 13, 2015 Report Share Posted December 13, 2015 Graeme, Shame you are so far from me, I would have been happy to give you the bolts you need, I've so many here, that I don't use ! Quote Link to post Share on other sites
kob666e Posted December 13, 2015 Report Share Posted December 13, 2015 Namrick are very helpful if you ring them up and ask the length of the shank on a bolt, have done this several times when ordering and seem to remember did much the same when I replaced the trunnion bolt, as previous owner used bolts with too short a shank. Quote Link to post Share on other sites
graeme Posted December 15, 2015 Author Report Share Posted December 15, 2015 Thanks for your thoughts, I won't fit the Grade 8 bolts unless the shank is the correct length and diameter. It wasn't the cost that bothered me, I will have to order from Moss Europe or US and I was just looking for a local alternative. Cheers Graeme Quote Link to post Share on other sites
BlueTR3A-5EKT Posted December 15, 2015 Report Share Posted December 15, 2015 Thanks for your thoughts, I won't fit the Grade 8 bolts unless the shank is the correct length and diameter. It wasn't the cost that bothered me, I will have to order from Moss Europe or US and I was just looking for a local alternative. Cheers Graeme Try The Roadster Factory or Aircraft Spruce https://www.aircraftspruce.ca/categories/aircraft_parts/ap/menus/ha/bolts.html Peter W Quote Link to post Share on other sites
BlueTR3A-5EKT Posted December 15, 2015 Report Share Posted December 15, 2015 (edited) 139835 bolt.pdf Here is the drawing I did in 1989 to get the correct item remade file:///Users/admin/Desktop/139835%20bolt.pdf Edited December 15, 2015 by BlueTR3A-5EKT Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.