Hotshot very nose heavy under braking

[carparkthrasher 1]

Hi all,

After a weekend spent building my re re Hotshot I am pleasaed to say it goes like the clappers and is coping well being blast around my front garden and the road outside my house. My only query is probably a self answer sort of thing but..........

She is very nose heavy - is this normal for Hotshots? Anything close to a jump/bump will see the nose and its massive bumper bury itself in the ground and the car goes A over T. I guess this is to be expected but the thing I am not sure on is why when under full braking, the nose comes down so much that the bottom of the chassis will hit the road. Is this normal or have I got something wrong in the build? She drives ok and I am pretty sure all is in order so I think it will come down to being a personality trait of the Hotshot - do you agree?

Thanks

CPT

[HunterZero 76]

Yes, it's normal, but it's not really that the front of the car is too heavy. The main problem is that the Hotshot is very undersprung at the front, the shock unit is very soft. You can use the collar to load up the spring which will help a little, but won't eliminate the problem entirely.

The best vintage hopup for the Hotshot is the Supershot style HP suspension kit, which does away with the monoshocks for one damper per corner, if you can find it.

The RC Channel Hotshot kit has parts for 4 shocks, but all that metal does add a lot more weight to the car.

- James

[Percymon 2184]

As James says left with the spring set at its lesast compressed state its pretty useless - you need to wind the collar round one, if not two notches to firm it up. Even then it still nose dives and bottoms out. The Hotshot isn't the lightest buggy around either, which doesn't help.

You could shave 200g of weight by swapping a big NiMH pack over to Lipo, although that may make things even more nose heavy !

[carparkthrasher 1]

Cheers both for thoughts, as suspected it is inherent to the beasty!

[Saito 5]

The geometry of the Hot Shot's front monoshock is all wrong. Tamiya recognized this and altered the design for all other incarnations of the buggy that followed it with a monshock front end. The HS shock has its mounting points below and inboard the actual shock. As such, the mount points and shock travel in different paths resulting, among other things, in thrust loading to the shock body itself. Futhermore this setup allows for an "over center" point to be reached in the shock's compression stroke. Once this point is reached, the springs ability to "hold up" the car falls away dramatically and the front drops to the ground. Tamiya compensated by giving the shock a very stiff spring, but its a band aid at best. The Boomerang (and Hot Shot II/Super Saber) solved this by adding parts B11 and B10 over the existing HS mounts to relocate the mounting locations. The new locations properly compress the shock from the outer ends inward thus resulting in one linear smooth stroke. These "B" parts should be able to be retrofitted to the HS front end along with an appropriate CVA "short" type shock unit if you wanted to retain the monoshock front end style.

[carparkthrasher 1]

Right, further to Saito's suggestion - I have just ordered the parts to make this plan happen! I like the mono shock approach so will give this a go and let you know how it turns out!

[carparkthrasher 1]

Right, further to Saito's suggestion - I have just ordered the parts to make this plan happen! I like the mono shock approach so will give this a go and let you know how it turns out!

Hi all! Finally an update on this!

As suggested, using the Boomerang B parts works a treat! So the front end now has a CVA shock with B11 and B10 to bring the movement to the more usual - from the out in not halfway along the shock! With the original spring back on it this shock works really well and the nose diving has gone!

CPT

[lucasan 28]

Hi all! Finally an update on this!

As suggested, using the Boomerang B parts works a treat! So the front end now has a CVA shock with B11 and B10 to bring the movement to the more usual - from the out in not halfway along the shock! With the original spring back on it this shock works really well and the nose diving has gone!

CPT

So which shock did you end up using?

[carparkthrasher 1]

So which shock did you end up using?

Hey! Sorry for delay, I used a CVA short shock but with the spring as supplied with the Hotshot. This combined with the better mouting position of the B parts maeks all the difference.

[lucasan 28]

Hey! Sorry for delay, I used a CVA short shock but with the spring as supplied with the Hotshot. This combined with the better mouting position of the B parts maeks all the difference.

What part # is the short shock? Thanks again. Would love to see a pic of what you did.

[BennySRB 0]

I've just built a re re hotshot and have the same problem. Do you have the details on what changes I need to make?

Thanks

Ben

[Wandy 1529]

I've just built a re re hotshot and have the same problem. Do you have the details on what changes I need to make?

Thanks

Ben

Read Saito's post in this thread ...

The geometry of the Hot Shot's front monoshock is all wrong. Tamiya recognized this and altered the design for all other incarnations of the buggy that followed it with a monshock front end. The HS shock has its mounting points below and inboard the actual shock. As such, the mount points and shock travel in different paths resulting, among other things, in thrust loading to the shock body itself. Futhermore this setup allows for an "over center" point to be reached in the shock's compression stroke. Once this point is reached, the springs ability to "hold up" the car falls away dramatically and the front drops to the ground. Tamiya compensated by giving the shock a very stiff spring, but its a band aid at best. The Boomerang (and Hot Shot II/Super Saber) solved this by adding parts B11 and B10 over the existing HS mounts to relocate the mounting locations. The new locations properly compress the shock from the outer ends inward thus resulting in one linear smooth stroke. These "B" parts should be able to be retrofitted to the HS front end along with an appropriate CVA "short" type shock unit if you wanted to retain the monoshock front end style.

....and this is what your car should look like at the front end.

[BennySRB 0]

Thanks, the pic really helps, I wasn't sure what part of the B tree was used:

Makes more sense now, short shock 80mm right?

Thanks

Ben

[Wandy 1529]

Thanks, the pic really helps, I wasn't sure what part of the B tree was used:

Makes more sense now, short shock 80mm right?

Thanks

Ben

Yep, Hotshot 2 & Boomerang used the short 80mm CVA at the front.

[JeepnMike 150]

Just to add a grain of advice to this thread, the throttle will alter the nose-diving of your car when you hit jumps. Next time you hit the same jump, don't let off the throttle (usually a first response), give it a bit more gas or at least stay neutral on the throttle, your car will fly a lot more level.